'84 GSL-SE No Start
 

I have a 1984 GSL-SE that is completely stock with no mods.

Here is a history of the issue: I do not drive the car often, typically only 1000 miles a year or so. It sits in a climate controlled garage otherwise. The car always ran very strong and smooth with no signs of issues. When I last drove the car, it was on about 1/4 of a tank, so I filled up to the top with fresh ethanol free gas before returning home. I parked the car and came back to it a couple months later to take it out for a maintenance drive. The car would not start. I followed the usual de flooding procedures and still nothing, noting that there was zero gasoline on the plugs. I was and still am working 7 days a week at this time, so the car sat untouched for a few more months after this. I just recently finished fixing up a 90 Miata and sold it, and now have a bit of time here and there to work on the SE.

Here is what I have tried so far: Tested for spark. All four plugs produce a strong spark when placed on the top of the intake manifold and cranked.
Checking the operation of the AFM flapper to ensure that it activates the fuel pump when pressed in with a finger. It does.
Checking for fuel flow by removing the fuel hose from the fuel pump to the fuel rail, and jumping the fuel pump jumper connector next to the intake box. Fuel pump flows an estimated 1/2 gallon per minute into a gas can.
At this time I noticed the less than 1 year old fuel looked and smelled stale. I took the opportunity to drain the fuel tank by extending the fuel hose and allowing the fuel pump to pump the fuel into a gas can. As soon as fuel flow stopped, I turned off the ignition and added 3 gallons of brand new ethanol free gas.
I reconnected the fuel hose to the fuel rail, and turned the ignition on to get fresh fuel to flow through the fuel rail and to the return line, allowing the fuel pump to run for about 5 minutes like this.
I tried starting the car again, hoping that it was a bad fuel issue. No luck, spark plugs still dry.
Next I tested fuel pressure. Since the car does not run, I can only test fuel pressure with the ignition on and the fuel pump jumped. I got a stable reading of 39 PSI at the hose going into the fuel rail, when the pressure gauge was tapped in using a 3-way connector.
Next I checked the connection of the blue spade connector on the trailing coil. The connection is good, and I have continuity between this connector and the "injection" and "computer" fusible link connections. (Can someone confirm if this is the correct test procedure for checking if this connection is good?) I also checked and cleaned the fusible links and their connections. All fusible links are good and have battery voltage.
The tachometer does bounce up and down when trying to start the engine, further confirming the trailing coil connection is good. On occasion I have noticed the tach spike to over 1k while trying to start despite no audible change in cranking speed.
I also tried moving the blue spade connector from the trailing coil to the leading coil. No change.
Spark plugs are fairly new and clean.
Cap and rotor were replaced less than 5k miles ago and still look new.
Battery is kept on a float charger so it stays topped off between work sessions.
Engine does catch and try to start when spraying starting fluid into the intake, but I do not have anyone to help me, so all I can do is spray some in then walk around and try to start the car.

I am unsure of what to try next. It seems that the injectors are not injecting any fuel - but what is the cause.
Could both injectors have failed in the couple of months between my last drive?
Could they both have clogged?
Could my ECU have failed?
Is there any other sensor or wire I need to check?

I'm a 12A guy and not versed in the fuel injected subtleties, so take this with a grain of salt. It sure seems like you've done lots of good troubleshooting.

Have you ever unplugged the electrical connectors to the fuel injectors? I ask because here in the forums people have said that they are polarized, however the plugs can easily be reversed and render the injectors inoperative.

My next steps would be to check for power at the connectors to the fuel injectors and then to check the fuel injectors on the bench.

I have not touched the injectors as they are buried deep under the 'dynamic chamber' upper half of the intake manifold and cannot even be seen without removing this large component that has lots of other stuff connected to it. That was where I was probably heading next with diagnosing this, but I was hoping to avoid having to remove that thing. One of my next things to test was back-probing the ECU wires to see if the ones relevant to EFI have proper voltage as well.

I'm going to build myself a System Checker 83 to test for ECU error codes, according to this thread: https://www.rx7club.com/1st-gen-arch...ite-up-285461/

I will report back with the results once I get the bits and have time to do the work, but in the meantime if anyone has anything to add, please do so.

Have you checked the fuses for "Engine" and "Meter Back" inside the drivers footwell area? This is a block of fuses which provide power to the various fuel injection components prior to the ECU. This could be a simple fix, and with the other stuff you've tested good, I doubt it's anything under the hood to be honest. The trick you used to swap ECU trigger for fuel injection from Trailing to Leading Coil proves that your ignitors and coils are likely working fine. I also doubt its a problem with the injectors. Here's a shot of the fuse block for reference:
https://cimg2.ibsrv.net/gimg/www.rx7...241c56617a.jpg
Also, what did you work on last? Anything having to do with engine electrical?

As the Bosch L-Jetronic system in these cars is very simple, there's also not a lot to go wrong. Report back with what you find,

I did check the fuses during my initial diagnosis months ago, and they are good. I re-checked them just now, even using my multimeter to confirm they have continuity, and both of the fuses in question are good. All other fuses are also good upon visual inspection.

Last work I did on the car was changing the oil right around a year ago.
Prior to that, I did some brake work and replaced the plugs, wires, and cap/rotor, and all this was years ago. I've never done anything electrical aside from ignition maintenance on the car.

Thanks everyone for the help so far.

How many miles are on the original engine? How does compression sound when you spin it with the starter without the plugs installed? What's the outside air temperature when youve tried to start it?

Low compression usually shows up with difficult hot starts, but if a seal or two is carbon locked, you may not be getting enough compression for a solid start. You may be onto something with fuel rail, but both pressure and volume at the rail looked good. Fuel injectors are pretty solid, though the leads and connectors on them are the weak point - if you've never replaced the connector pigtails.

Quick and easy check is to thread a mechanics stethescope through the upper intake manifold runners and listen for them ticking when someone cranks the engine. They're both easily seen from above, and a long slender probe can reach the orange top of each injector.

Be sure to remove your Fuel Injection Test Shunt at the Air Flow Meter after all of your testing is done...

The original engine has 301,594 miles on it. Compression sounds strong and consistent when turning over with plugs in, and on the last drive the engine ran very smoothly with no signs of power loss. I have had a bit of trouble starting the car when it was hot just a couple of times, like going into a store, then it took a bit longer to start when I came back out, but no consistent problems in that regard. Temperature in my garage is about 65 degrees.

Here is a video of me turning over the engine with the plugs removed. It sounds normal to me, perhaps one of the pulses being slightly weaker than the rest. I'm not an expert on how these should sound though.
https://streamable.com/2ty5qi

I don't have a compression tester, or a mechanics stethescope. Might need to get those. Should I try a MMO decarbon?

Also probably unrelated, I found this single loose wire when I removed all the plugs. The wire is black with a green stripe and a red/orange band about every inch. It is coming out of the harness that runs next to the oil filter along with two other wires, one that appears to be going to the oil pan and another to what could be a coolant temp sensor just below the oil filter. Not sure where it goes or if it is supposed to be unused.

https://cimg7.ibsrv.net/gimg/www.rx7...184db3383a.jpg

Is that a typo? 301k original miles? Confirm,...

Some observations;
1) in your video, its spinning over VERY fast, which could mean you have no compression. Without compression, the engine won't be drawing much air into the intake, and as such, won't be opening the Air Flow Meter door which activates the fuel pump, which would explain no fuel flow at the injectors and dry plugs.
2) your extra wire - I went out in the garage and looked closely, but can't nail down exactly what that goes to by looking under the hood. Single-spade connectors in the immediate area include: oil pressure sender (*can't visualize in your pic), engine temp coolant sensor right next to it, the ignition condenser functions as a noise attenuator, and the A/C clutch engagement lead which goes forward to the compressor. However,...
3) FSM says that's the color code for Oil Level Warning Light, code BG(YR) = Black, Green stripe, Yellow/Red tracer, as shown here on page 15-26 of the 84SE FSM:
https://cimg6.ibsrv.net/gimg/www.rx7...e5f1985897.jpg
This wire connects to the oil level sensor and while it won't prevent the engine from starting, it will show a dash light for Oil Level and should be connected at the DS of the oil pan, right next to the Oil Temp Sensor.

A sidenote; if your mileage is correct, first off - CONGRATULATIONS! This would make your 13b the highest stock mileage I've ever heard of! Most 13b engines of the Series 3 cars tended to lose compression at about 215-220k miles due to a combination of side seals and Oil Control Rings going bad at about the same time, leading to high oil consumption, smoking out the tailpipe, and difficult hot starts. I replaced my original engine at 221k miles, and several other S3/SE owners have had very similar mileage.

Here's a trick to try; take some engine oil and a turkey baster or similar squirting device and shoot a few ounces of engine oil into the Trailing Plug holes. Rotate the engine by hand a few revolutions by sticking a socket wrench on the Alternator Pulley, and give it a few minutes, then try to start it. Extremely dry seals and housings won't build compression on a marginal engine. Introducing some oil may seal things up enough to get it to catch. Good luck, report back,

Yes, 301k original miles. I have a stack of maintenance records from the first owner that go back to 1984, about an inch thick. Nothing in the records indicate anything about any major engine internals ever having been worked on. The car actually has an interesting history - The first owner owned the car until she passed away in 2008, she even put the car in her will to have it auctioned off for charity. The car had 291k in Dec 2008, so it has only been driven 10k since then. The next two owners owned the car only briefly until I bought it in 2012, if I recall correctly. There is actually a post about the car here: https://www.autoblog.com/2008/12/10/...-a-good-cause/
Because of this, I have a great deal of respect for this car and want to keep it running well and 100% stock.


In the first video I posted, the spark plugs were removed, and the engine spins over much much slower with them in. Here is a video of me trying to start the car after spraying oil into the spark plug holes, spinning over the engine slowly by hand, waiting 10 minutes, then installing the plugs and plug wires: https://streamable.com/96mkuf
Also, when I tried to start the engine with the air filter box removed, I could hear the door of the AFM flapping open and closed, it made a loud clunk clunk each time air was sucked into the intake. I noticed no difference in the speed the engine turns over with the spark plugs in after doing the oil spray trick. Unfortunately the engine did not want to start. I am still waiting on the LEDs and connectors to make my DIY System Checker 83 and will report back with results of that when I get the bits and do the work.

When I spun the engine over by hand, I could hear puffs as the compressed air was being pushed out of the spark plug holes, even though I was only spinning the engine with a wrench. After I installed the spark plugs, I tried to spin the engine over again with the wrench, and it actually wanted to spin back the other way against the compression, but I was able to overcome it with the wrench.

As for the oil level sensor, my oil level sensor is plugged into a red and yellow wire with what appears to have an orange or red tracer ring. It is using a plastic clip connector. You can see it, covered in grime, sitting just above the oil cooler line in my image. The second sensor in the service manual image you posted, situated just above and to the right of the oil level sensor, is not present on my car. I even put my phone down there recording a video to see if anything is there, and the oil pan completely lacks any sort of sensor there. The oil pressure sensor (Just below the oil filter?) and the coolant temp sensor are visible in this image.

https://cimg4.ibsrv.net/gimg/www.rx7...2e41356029.jpg

Well, you're doing all the right things! The cranking video you posted sounds fine (plugs in), though your comment about the AFM door flapping open and closed is unusual. When the engine draws in air, there's some pulses in suction depending on the rotation speed, but I've never noticed any clunking during crank. The fact that it's audible means there's nothing blocking the intake path, though.

Some additional thoughts; your last video shows a fuel gauge at empty - how much fuel is in the tank now? I know you added fresh fuel recently. Let me think on this for a few hours and see what else I can come up with. You seem to have checked everything obvious already,...

ETA; avoid the MMO treatment. There's a thing called good carbon that we don't want to throw into the mix just now.

About 3 gallons in the tank right now. I can add more if you think it might make any difference.

Also, I was considering pulling the return fuel line and checking if any fuel is making it through the fuel rail.

Just wanted to chime in... had my injectors serviced in 2016.. they were bad AGAIN in 2023.. must be that ethanol% these days. ( or bc the car just sits.. lol)

But anyways, sent 4 ( 2 spares) total to RC to service, 1 out of the 4 were still clogged/closed when I got them back. So definitely bench test the injectors and make sure they open, or it's a #wildGooseChase #GL

The fuel rail Is a very simple setup with a Pulsation Dampner on the end along with a vacuum assisted Fuel Pressure Regulator powered by intake plenum vacuum. The Pulsation Dampners don't tend to go bad on these, but if the screw in the end is loose or it's leaking fuel, you might take a closer look at it. As for the Fuel Pressure Regulator, think of it as a flow restrictor - as vacuum increases, that vacuum closes a valve leading to the return line, shutting the flow and effectively dead-heading the fuel rail, bumping up fuel pressure seen by the injectors. Fuel Pressure should be ~28psi at idle and bump to ~34-40psi with vacuum. Signs of a bad or disconnected FPR are lack of power at higher RPM and really good fuel mileage(!).

The only other thing I can think of is tied to the flapping AFM air door when youre cranking it. That seems odd to me. Take close look at the rubber air intake tubing, the air filter box, and anything else leading to the Throttle Body looking for cracked fittings, air holes, and anything else that could be letting in unmetered air, and releasing your vacuum at the intake. Could be that when the engine shakes during cranking, something comes loose or opens up an air gap that allows the AFM air door to slam shut, turning off the fuel pump (*as long as you've removed your Test Shunt...). I'll keep noodling on it,

Here is the source of the sound I mentioned: https://streamable.com/ohvgcx

And here is what it sounds like while cranking: https://streamable.com/dp810r

Note that you can't hear this when the air filter and filter box cover are installed.

I still have the fuel pump shunt in, so it is still running any time the ignition is on.

I'll get a better look at the intake piping while cranking to check for cracks or loose joints. Right now the passenger side is about 6 inches from the wall of my garage, so I'll get to that when I move the car to check the ECU.

EDIT: I tested to see if fuel is exiting the fuel rail, and it is. I went ahead and added another gallon of fresh gas since I drained a bit during this test.
Also, while cranking, sometimes I see the tach 'jump' up above the actual RPM, here is a video showing that: https://streamable.com/u4edtl

Your 2nd video above of what he AFM door sounds like when it's cranking does not sound normal. In fact, the cadence of when it's slamming shut would have me believe that you have an Apex Seal stuck or missing on one of the rotors that's preventing a steady flow of air. This should not prevent a start, however if an Apex Seal is stuck down, you're missing 2 chambers of volume, not just one, and that's 2 out of 6 total, which is substantial. The intake pulse on a good engine is very slight, and not enough of a loss between pulses to allow the AFM door to close.

I still hope it's something simpler, but that's what I'm hearing in your videos.

Another thing you can try is pull-starting it using another vehicle and a tow strap. Be advised, this takes some effort and could damage the engine further if the seal comes dislodged and falls out of its slot, but pulling the car up to 10mph and releasing the clutch in 2nd gear will likely spin the engine fast enough for it to start. On tired engines with poor compression, this can usually get you home, but we're pulling at straws at this point.

The high mileage on the original engine is definitely in the back of my mind. Plus, your posts so far read like a diagnostic manual on troubleshooting. You've done all the right things, and yet - it's still not running. Let us know your thoughts, and take a deep breath - your car has an amazing story behind it, and 13b engines are readily available. Even Mazda still sells 13b rotor housings for rebuilders. Good luck, man.

The high mileage is something that has always been in mind for me, and I knew a rebuild would be coming eventually. 300k is a great run for a 40 year old rotary. But before I buy a compression tester I want to rule out all other options.

The spark plugs being totally bone dry even after extended starting attempts makes me want to verify that fuel is actually getting into the engine. Is there any way to 'trick' the engine into injecting more fuel than normal during a starting attempt? I want to see some fuel on the spark plugs. Is my only option to verify that the injectors are actually spraying fuel to pull them loose and try to start the car with the injectors still hooked up to the fuel rail and look for any fuel spray? Is that even advisable?

Tomorrow I am going to move my Miata and push the RX-7 to where I can actually access the passenger side, and have someone come help me to spray starting fluid and see what happens. I'm still waiting on my 12v LEDs with pigtails to arrive so I can check the ECU for errors (Shipping is slow.)

While we are talking, I have a couple of questions.
If I end up needing new injectors - Should I only get used stock injectors, or are the "modern replacement direct fit" Denso injectors I am seeing on ebay, that come with an adapter pigtail any good?
Second, if I end up needing a new engine, does anyone know of a good engine builder and installer in the southeast? Installing an entire engine is likely beyond my capabilities and I would like to look into having a good rotary shop do that instead. I'm a computer technician by trade, so I'm not bad at diagnosing things and replacing bolt on parts, but I've never replaced an engine, transmission, or done a timing belt or intake manifold replacement.

Sorry for the repeat posting.

I tried spraying four seconds of starting fluid into the intake by removing the breather hose at the top of the black intake pipe just before the throttle body, spraying in there, then putting the hose back on and trying to start it. Here is the result: https://streamable.com/4crzxj

I tried this again while standing outside the car and sprayed more into the AFM's intake, here is the result of that: https://streamable.com/tzv2lk

The engine purrs when it has something to burn. I still feel like this is a fuel issue. I'm going to keep working at that until proven wrong. Feels good to hear it spinning, even if its just on starting fluid.

I also noticed a suction sound coming from the rat's nest near the distributor/oil filter area after the engine shuts off. Sounds like something trying to suck air and fluid through a tiny hole. Could a vacuum leak here cause a no start?

Hey! That's encouraging!

You may be right that it's fuel starvation. The FSM has a page that talks about testing the fuel spray pattern with the injectors loose but mounted to the fuel rail using coat hanger wire to hold the seals together. I don't recommend it, because it's spraying vaporized gasoline all over the engine! However, here is the FSM troubleshooting guide, along with the Fuel Injector in-vehicle test protocol:
https://cimg2.ibsrv.net/gimg/www.rx7...05e42d902e.jpg
https://cimg0.ibsrv.net/gimg/www.rx7...34e6f1dc6e.jpg
Did you order a mechanics stethoscope with the long wire probe? This would make listening to the injectors easy, as the probe can be inserted between the UIM runners, as both injector tops are visible from above. If you hear clicking, they're getting electrical signal, at least. They could still be clogged, but at least the wiring harness and pigtails would be proven good.

As to replacement Injectors, the Series3 SE uses 680cc, Low Impedance Injectors and factory used are better than aftermarket based on forum user input. E bay and Rock Auto replacements are questionable at best. I tried some "Scorpion" brand injectors and RC Engineering couldn't get them to flow properly, and I ended up using one of my originals and a OEM replacement after cleaning and rebuilding. They're fast, if you have time to send them out - and when you get them back, they're 100% good to run.

The fact that it's running on supplemental "fuel" (*starter fluid) negates my previous comments about sealing and compression. Focus on fuel, namely Injectors and the pigtails that connect them - they get brittle and can lose contact after the retention tabs crack off. Borg-Warner sells new pigtails if you need them.

Added; you asked about a slight,vacuum hiss after shutdown, and that's normal. The Vent & Vacuum solenoids tend to bleed off pressure or vacuum and you can hear this after the engine goes quiet. Additionally, the Brake Booster is in the vicinity and also stores some vacuum which bleeds to atmosphere.

One other question; when you parked it before this trouble started, did you take it for a good, long drive, getting it fully up to temperature before parking it? I ask because that's how carbon locking occurs on these engines. Mode of action is that someone pulls the car out of the garage to wash it, running the engine for less than a minute or two, washes the outside of the car, and then the engine either won't turn over (*carbon locked) or starts but runs wonky (*carbon stuck an Apex seal).

You may have several things going on, but focus on Fuel, first. Good luck,

Last time I drove the car, my wife and I went to eat (about 10-15 minutes drive to the place) and shut it down, ate, then came back out to go on about an hour long drive on some twisties, then got gas, went home, shut it down. So no short drives. I always let the car run for a minimum of 10 minutes, ideally with running it through the gears before shutting it down. We've been a rotary family since I was born (My dad had R100s, RX2s, and RX7s) and know the normal rotary stuff.

I'll be heading over the Harbor Freight to buy a top-quality, surely better than snap-on, stethoscope and a set of back-probe leads along with a different multimeter that has removable probe leads (Mine does not.) The LEDs for making my system checked 83 should be arriving tonight so I can get started on that diagnostic as well.

My list of diagnostic possibilities is narrowed down to this:
1: ECU is not getting a signal from the trailing coil due to the black wire in the blue spade connector being damaged (Does this same wire feed the tachometer, or does the other wire in the blue spade connector feed the tach?)
2: ECU is not sending the signal to fire to the injectors due to the ECU being faulty (Perhaps bad capacitors leaking their juices out onto the board?)
3: Injector wiring damaged.
4: Injectors clogged.

I will report back with test results.

I have a sinking suspicion my gas tank may look like the one in this thread: https://www.rx7club.com/1st-gen-gene...creen-1164119/
Hopefully not the case, but I will be replacing my fuel filter after this regardless.

Update with a question:

I got the stethoscope, but I cannot see the orange top of the injectors at all through the runners of the dynamic chamber. I can clearly see the fuel rail, pulsation dampener, and the rear most part of the fuel pressure regulator on the back of the fuel rail. The injectors are closer to the middle of the fuel rail. Is the only way to see them to remove the black intake tube so I can see through the center opening of the four runners?

I did the test anyway, pressing the long probe of the scope directly onto the fuel rail. I had my wife turn the key on (fuel pump jump still in) and could clearly hear the flowing of fuel through the rail. Cranking the car, I could not hear even the faintest ticking or clicking sound, but the sound of the engine turning over was clear and loud. Can you hear the injectors by pressing the scope to the fuel rail?

EDIT: Update with photos of how I tested.

https://cimg5.ibsrv.net/gimg/www.rx7...df9dcccd48.jpg
https://cimg1.ibsrv.net/gimg/www.rx7...cea6fb43fb.jpg

A few responses here;

1: ECU is not getting a signal from the trailing coil due to the black wire in the blue spade connector being damaged (Does this same wire feed the tachometer, or does the other wire in the blue spade connector feed the tach?) Your tachometer is bumping when you try to start it - I'm betting the signal is getting through. The trigger for the Injectors is shared with the ECU and Tachometer, so I've never seen a case of one but not the others...
2: ECU is not sending the signal to fire to the injectors due to the ECU being faulty (Perhaps bad capacitors leaking their juices out onto the board?) Unlikely- the ECU on these cars is pre-OBDanything and rudimentary simple, basically storing a hard-core fuel map for open loop, and the very minimum for closed loop operation (*when in 5th gear). The ECU doesn't typically go bad, but wiring should always be checked cautiously. This would be a low priority for me...
3: Injector wiring damaged. MOST LIKELY CAUSE.
4: Injectors clogged. NEXT MOST LIKELY CAUSE.

In your pic, where your probe is inserted is almost directly above where the top of the injector sits. Where you're pointing to the fuel rail, follow that down about an inch toward the block and you'll see the top of the front Fuel Injector. For the rear injector, you may have to probe from the left side of the air tube. You don't have to remove the air tube to reach them, in fact, listening for them can be done with a running engine with it all hooked up and working.

You MAY be able to hear injectors clicking through the fuel rail, but I've never tried that. The rubber seals at the top of the injector probably damp quite a bit of noise.

To jog my own memory, I went out in the garage to be sure I could reach both Front & Rear Fuel Injectors, and I could with some maneuvering. I've tried to show where the probe needs to go to touch the top of the injector, but you may have to poke around a bit. Sorry, I only have 2 hands holding a probe, a flashlight, and my tablet, then clicking to take the picture! Rear injector to the left, and Front injector to the right;
https://cimg1.ibsrv.net/gimg/www.rx7...d40086dd2c.jpg
Also, note that you can bend the probe rod a bit to angle in if needed. Honestly, a bent wire hanger might work as well, as you could feel the inector ticking on your fingertip once you're on it, but hearing it is unmistakable.

Thanks for the help and the pictures!

I was able to find and get the scope onto the injectors - With your photos plus looking up what the fuel rail looks like when removed from the car, I was able to understand the geometry better. I can visually see a bit of orange on the front injector, but the back injector is still not visible, but I could feel it with the probe. Alas, no one is able to turn the key for me at the moment, so I decided to use my free time tonight to check the ECU.

My LEDs arrived, and I built my DIY system checker 83. The ECU displayed no error codes, even after trying to start the engine. I tested to ensure the diagnostics were working properly by disconnected the blue spade connector on the trailing coil and trying to start the car, and the code for that appeared. I also tested disconnecting the throttle sensor, and the code for it also appeared, so diagnostics are working properly.

I followed the instructions for checking the ECU found in this PDF, on page 4B-70: http://wright-here.net/files/manuals...ssions_13B.pdf


https://cimg1.ibsrv.net/gimg/www.rx7...1432d2fa3a.jpg

All voltages were within the expected range, except the throttle sensor was 2.14v instead of the expected 1v. I doubt this is the cause, but felt it was worth noting. To be thorough and test, I placed a folded piece of paper between the throttle sensor and the piece that pushes it in until the reading was about 1v, then tried to start the car, and of course no change. Does this sensor need to be adjusted somehow? I noticed solenoids clicking on and off as I pushed the throttle sensor in with my finger. If I pushed it in slightly, I would hear one click. If I pushed it in further, I would hear a second click.
Most important: Both "Injector (#10)" and "Injector (#20)" read 12v when probed. I would assume if the connection to the injectors was broken, this would read 0v?
I did not test any voltages on the left side connector with the lowercase letters, as these seemed secondary to engine running.

I will report back tomorrow with final results of injector scope listening, now that I know where to probe. (Need a key turner.)
Looking like the problem is the injectors.

That all seems to test fine with your Volt meter. On the Throttle Sensor (*aka Throttle Position Sensor or TPS), that will be a highly variable reading, depending on how the TPS has been adjusted. On the SE, the TPS controls so much of the idle circuit for idle quality that its very mich a tinker until you find the right setting kind of thig. I've written full instructions on how to set TPS many times over the years, but I would say: if it ran well when you parked it - DON'T CHANGE THE TPS SETTING. Doing so would throw the whole thing out of balance and you'll be chasing all manner if weird issues... Same for Idle Speed, Air Bleed, and Idle Mix. Leave all of those alone for now, as you need a running engine to fine tune any of those.

As for the Injectors, the voltage you measured at the ECU connector is power coming FROM the ECU to the part in question, right? (I haven't studied this part of the diagnostics...). If yes, then that still leaves wiring TO the sensor or device as an area to check, i.e. going to the Injectors and measuring pulsing 12v at each Injector pigtail when cranking ensures that your 12v is getting to the Injector. A 12v constant power to the Injector runs it WOT, per the FSM test for fuel flow, so I wouldn't expect to see 12v constant OUT to the Fuel Injectors.

If the 12v pulsing to Injector pigtails when cranking tests good, then it's bad injectors - but you'd know that by listening to them, as they wouldn't be clicking open and closed when cranking, possibly due to gumming up the plunger, or an internal short. At this point, I'd have removed the UIM and be looking at the pigtails, connectors, and the Injectors themselves, because I had to replace the pigtails in the past due to connector brittleness cracking the retention tabs. Theres a thin wire spring clip that locks the connector to the Injector, and without the plastic tabs, the pigtails pull right off.

Even if you wanted to send the Injectors out for cleaning, you'd need to remove the UIM. It can be done in about 15min, if you're shying away from that for some reason. It would be prudent to have a new UIM/LIM manifold gasket in hand before doing it though, as the original paper gasket is likely to be ruined on removal. Plus, while you've got it apart, might as well do a full LIM & 6-Port cleaning if it's never been done, and then you've got the whole intake apart...!

Let us know what you hear at the Injectors under cranking. Wish you were here - this all goes faster with 2 sets of brains looking at it!

I was able to get the key turned for me with the scope directly on the orange plastic of the front injector, and I could not hear even the slightest ticking of any sort, but could clearly hear all the other noises of cranking coming through the scope. I think I got the rear injector too, but couldn't actually see it from above or the side. No sound there either.

Going to be removing the dynamic chamber/UIM now. I assume the gasket I need is N304-13-114A ?

Once I get the UIM off, to test the injector wiring/pulses, can I just wire in a 12v LED just like how I did with the ECU diagnostic port?

Also, I was on the Mazdatrix website and found an "Injector inlet filter" https://mazdatrix.com/product/inj-in...92-inj-filter/
Is this something my car has, or is this an upgrade that Mazdatrix sells, and should I get them?

It took me about two hours to remove the dynamic chamber and the injectors.

Problem found.

Both injectors are completely clogged with reddish-brown goo and particulates.


https://cimg7.ibsrv.net/gimg/www.rx7...0f35708cf8.jpg
https://cimg8.ibsrv.net/gimg/www.rx7...d488a11053.jpg
https://cimg9.ibsrv.net/gimg/www.rx7...56d1d775ba.jpg
https://cimg0.ibsrv.net/gimg/www.rx7...82fe574126.jpg

One of the injectors I cleaned off the top before taking pictures. The other I did not.

Course of action: Test injector wiring still, its probably fine.
Get injectors sent off for cleaning, or just buy a pair of used ones right now and send these off to be cleaned and kept as spares.
New fuel filter.
Possibly new fuel pump.
Get gas tank checked, cleaned, and relined if necessary.

Is it safe to send an inspection camera down the fuel filler neck, or is that risking an explosion?

Might want to also check your tank. Just run the fuel pump into a bucket.

I drained the entire tank using the fuel pump already, and the gas that came out was stale with a small amount of dirty water at the bottom of the first gas can I filled up (I drained out about 11 or 12 gallons) The dirty water that came out didn't have any chunks in it, but that must still have been enough to clog the injectors. Time for a tank inspection for sure though.

Well, you found the problem!

I've never seen those Injector Inlet Screens before. I wouldn't buy them, but I would recommend buying 2 sets of these (*pintle caps - the spraying end, and lower grommets where the Injectors mount to the engine center housing);
https://cimg0.ibsrv.net/gimg/www.rx7...f41e8b519b.jpg

Who knows how long these parts will still be available from Mazda, and when you find replacement Injectors, you may need these parts to recondition them. Whatever you find, I highly recommend sending them to a Fuel Injector repair facility to get them cleaned up, flow tested and spray pattern balanced. Since the Series3 intake only uses 2 Injectors - one for each rotor - it's critical that you get a good, matched spray pattern for best performance.

You're onto the root cause of the fuel tank needing work. That you removed rusty water from the tank is a good sign that maybe the fuel pump sent some water up front which caused the rust issue at the Injectors. Regardless, since the pump is running fine, I'd remove the Fuel Injection Hose from the inlet on the pump and check the wire screen filter there for rust and sediment. Then, replace the metal, high pressure Fuel Filter while you're under there, and lastly, flush the Feed and Return lines to be sure you got it all. The Fuel Pump is probably fine, they last nearly forever (*and are $345 last time I bought a spare...).

In the meantime, also inspect the Injector pigtails for damage and replace, if needed. Otherwise, I'm about 99% confident that once you get it all buttoned up again, it should start right up. Let us know how it goes,

I'll be sending my injectors in to be cleaned and tested.

As for the injector inlet screens, it looks like the injectors have them inside already, and they can be replaced, according to Atkins: https://www.atkinsrotary.com/84-92-r...n-are964-.html
I think RC says they replace these as well when you get a cleaning done.

I've ordered a set of grommets and pintle caps, and I've also sent an email to RC asking if they can replace these if I send them in with the injectors.

My fuel pump has always sounded a bit 'off' with varying tones and pitches, like a failing computer fan, and who knows how long you will be able to buy fuel pumps at all, so I went ahead and ordered a new fuel pump along with the gaskets that go on the fuel tank for the pickup lines and level sensors, since the tank will need to be removed, opened, and cleaned anyway.
Here is a video with sound of the pump running: https://streamable.com/x0z6ij

Question about replacing the fuel pump and fuel filter - Do I need to get fuel line pinch off tools, or will only a small amount of gasoline come out when I pop these lines off?
Another question: For replacing the pigtails, all I need to do is cut the factory pigtail off the harness and splice in the new ones? One of my two pigtails broke one of the clips on the side off. These things are incredibly brittle after 40 years.
Third question: Should I add anything to the gas in the future to reduce the risk of this happening again. Sta-Bil is okay to use, right? What about any sort of pre-mix oil or other common 'fuel system cleaners'.

When you send the Injectors in, include the Pintle Caps with a note to use your parts. The rebuilders replace a lot of things, and the caps may or may not be included if they don't have them in the parts bin. Keep the grommets with you; these fit over the spray end of the Injector and seal the bottom of the Injector to the center housing, and would probably get lost along the way as they're not an Injector part, per se. There are also matching O-rings at the tops of the Injectors that seal to the fuel rail - these are typically replaced by the rebuilders.

On Fuel Pump, that pump doesn't sound bad, but it doesn't sound good, either. I'd keep the original one in the parts bin as a backup, since you ordered a new pump anyway. Fuel Pump replacement is easiest with the back of the car on Jack stands, crawling in from behind and once you remove the protective cover plate, it's straight-forward. The Fuel Injection Hose MUST be high pressure rated hose from the pump forward. You can't use standard fuel hose, as it will expand too much and burst. Fuel feed to the pump is easily accessible, but note that as long as there's fuel in the tank, its going to want to run out when you detach it. For this reason, empty the tank first with the drain bolt on the bottom. This will also help you remove sediment and rust from the tank. Once you catch it, screen it to see how bad the internal fuel tank rust might be. This should help you decide how you want to handle correcting it.

I mentioned this before, but you definitely need to replace the N304- FI Fuel Filter under there, as well. With the pics you shared above, your Fuel Filter is likely clogged up, and could be part of the noise you hear back there. Buy 2, so you'll have a spare, just in case anything else is still in the system and it gets flushed back into the tank.

Fuel Injector pigtails are available from Borg-Warner last I checked, and as long as you splice them in with solder and heat shrink tubing, taking note of the polarity of the original wiring, it's an easy fix. Also be mindful ofmthe spring steel clips that hold the connectors onto the Injectors so you can remove them in the future without damaging them. At 40yo, every plastic thing on these cars is brittle and fragile.

I don't use fuel additives, though some of you guys who store your cars may have better suggestions. My SE gets driven occasionally year-round, so I'm constantly cycling fresh gas into it. In the aviation world, you always store aircraft with full fuel tanks to limit the air gap, which allows moist air to corrode tanks and fittings. That might work if the car will sit for months to years. Around here, we get oxygenated fuels which are hard on fuel systems of this era - but it seems that either draining completely or cycling frequently has kept my car running well.

Can't wait to see the video of your startup once you get it all back together. Nice work sorting out the various systems to find the culprit. I knew once you got a stethescope on those Injectors, it would tell the tale. Report back,

Sidenote; while the Injectors are out for service, do you have the gumption to remove the LIM and clean the 6-port sleeves? It's only an over 6×12mm bolts and nuts, a LIM to engine gasket, and a time-consuming de-carboning of everything around and inside the sleeves. Something to consider if you have the time and inclination, but be aware that it miht open up to become a lot more work if you have broken crispy rubber seals or stuck rotary valve sleeves. Quick test: how easy is it to rotate the 6-port actuator rods? You should be able to rotate the bellcrank on each one by hand, but with resistance. It should hurt your thumb, but rotate about 100deg (*CCW for the rear port, and CW for the front port actuator).

I just got a set of 4 injectors cleaned by RC just last month, they included all NEW pintle caps and new grommets (top and bottom) when they were returned back to me. (didnt have to buy any from Mazdatrix)
( My only problem was that 1 out of the 4 came back still closed, and I picked the closed one to install 1st try, which furthered the frustrations...)

I fully intend to change the fuel filter before running the car, so that this doesn't happen again right away. I'll hold onto the new fuel pump until after I get the tank cleaned and lined, install the new pump, and probably change the filter again some time after that just in case.

As for the things on the LIM, I was not able to push them by hand, but I didn't push too hard as it felt like I was about to cut myself on them. The rods coming out of the round actuator things are clean compared to everything else around them, indicating to me that they do still open and close. I'm not feeling super adventurous with all the fuel system work still ahead of me, so I'll probably skip trying to clean anything in the LIM.


https://cimg9.ibsrv.net/gimg/www.rx7...cb6f00b0d9.png
https://cimg0.ibsrv.net/gimg/www.rx7...1ee56e0a1e.png

Your 6-port Actuators look good; I'd leave them alone, too. Let us know when your injectors come back, as I'm curious what the replacements rate as far as fuel flow and spray pattern. These things don't last forever, and buying a few known quality parts now buys years of driving down the road. Take care,

Psst,.. new guy - see Post #27. This is what he found:
https://cimg4.ibsrv.net/gimg/www.rx7...a25a3d0eb2.jpg
He's ordering new Injectors and waiting for them to arrive, I think.

Welcome aboard, and hope to see you around the forum!

Just an update, the injectors were sent off for service and should be arriving back in about a week. I've got the rear lifted up and the fuel filter bracket loose, but ran out of time so didn't finish the filter swap just yet.

I should have labeled all the bolts I removed from the UIM as well as I've forgotten which ones go where, but at least I took pictures during the disassembly to compare against.

Fuel Filter is a 17mm wrench for the banjo bolts and 19mm wrench for the filter to hold it stable when removing and installing the fuel lines. Might want to give it some time to depressurize (*if you've run the pump recently) or you'll get spray mist when you loosen the connections. Wear safety glasses.

Note also that there are copper crush washers on both sides of the banjo bolts, inlet and outlet, which can be reused as long as you don't drop them and lose them. Good luck, and can't wait to hear it running again soon,

New fuel filter installed. The old filter had a film of rust on both the inlet and outlets. I cleaned the fuel lines and bolts before installing them, and used the new crush washers that came with the filter from Atkins.

Any idea why the old filter failed to filter out the rust coming from the tank? Does it bypass once too clogged?

The good news is that the fresh gas that dripped out when removing was perfectly clean and clear, not the slightest tint of rust to it. Hopefully I should be able to at least drive it a bit to get the tank cleaned and sealed.


https://cimg3.ibsrv.net/gimg/www.rx7...817ef56b61.jpg

Nice work. The Fuel Filters DO NOT bypass when clogged. They tend to build up crap over time and even though there's plenty of filter volume, once they fill up with enough garbage, they restrict fuel pressure, which results in poor volume and spray pattern at the Fuel Injectors which results in poor performance. Since this is a gradual process over a period of years, I recommend SE owners change Fuel Filters about every 5-7 years if you're driving it regularly; more often if it sits for long periods, you have poor quality fuel in your area, or if your Fuel Tank is eroding.

To answer your question about the rust; my theory is that you had water in the fuel tank that went through the Fuel Pump, through the Fuel Filter, and that water was sitting in your Fuel Rail and Injectors for a few weeks to months, rusting the internals of the Injectors. The Fuel Filter doesn't care what liquid goes through it, and is only a sediment filter. This belief is supported by your observation that the fuel which came out of the tank showed no signs of rust. Water mixes with alcohol impregnated gasoline (*aka oxygenated gas), and it may have been drained out when you did your troubleshooting - as water is more dense than gasoline and settles to the bottom.

The first sign of Fuel Filter restriction is that the car will accelerate poorly above 3k RPM, and power will drop out suddenly at 4k RPM and cause jerking behavior at anything higher than that as the fuel pressure fluctuates at the rail. Usually, the car won't be able to accelerate in 4th gear at highway speeds due to reduced fuel volume and pressure and will barely hold speed, much less accelerate, when you floor it.

For the $57 cost of a new N304- Fuel Filter, I always keep a few in my box of spares, as they're cheap insurance. Going from a clogged filter to a new one feels like adding 50hp in 4th gear on the freeway When you step on it, it goes!

I have a tank with rust , not horribly rusted mind you, just 40 year old surface rust. After 12-14 months I start to get that 3-4k Hesitation. If you let the car sit long enough , the rust settles and causes major blockage. Since I have bought my car 7 years ago , I have gone through 5 gas filters. I always change them in pairs because the top filter starts to yellow and fatigue due to engine heat.

The only real fix is dropping and cleaning the gas tank.

It's a never ending war with tank rust .

Update: The injectors arrived back from RC with a clean bill of health after cleaning.


https://cimg4.ibsrv.net/gimg/www.rx7...d7a63a5294.jpg


I will begin putting the car back together over the weekend, hopefully get it running again!


In preparation of a gas-tank cleaning and re-seal, I ordered a new filter screen to replace my likely destroyed one. I followed this thread to find the part to order: https://www.rx7club.com/1st-generati...ution-1164133/
The thread shows Jaguar part CBC5649. I ordered the filter screen from JagBits here: https://www.jagbits.com/product/CBC5649.html


https://cimg7.ibsrv.net/gimg/www.rx7...96a55316d9.jpg
https://cimg8.ibsrv.net/gimg/www.rx7...9b85970d97.jpg


The filter screen that arrived is not the same as the one in the photos from the other thread. The photo on the site did indeed look different from the one in the other thread, but I hoped it would at least be the same size. The part appears to have been discontinued, and replaced with a different design that supersedes multiple previous filter screens from Jaguar. The filter screen I got appears much smaller than the original part, with far less mesh surface area. Do you think that this filter screen will do the job? JagBits says that it replaces the older part, so if it is good enough for the Jaguar fuel pickup, perhaps it is good enough for an RX-7 fuel volume as well. The mesh does not appear to be as fine as the others, either.

If anyone has a better part to use for replacing the GSL-SE fuel pickup filter screen, please let me know. I want to use the best part possible for this.

What matters is the flow rate; did you read anything in the paperwork about max flow rate or similar? I would think it'll work fine, as most of the vintage Jags would be V6, V8 and V12, and well above what our 2 tiny (680cc nominal) injectors require.

Plus, keep in mind that the Fuel Pump inlet hose is larger than the others because it's low-pressure. This gives a lot of volume to the pump, which then converts it into lower volume, higher pressure. Your filter is doing the fine filtering, and is located after the pump.

Good news and bad news.

Good news first. It runs!

The old gasket had hardened into Stalinium and required substantial effort with multiple fresh razor blades and multiple soaks in Permatex gasket remover.
After cleaning off the old gasket from the UIM (Took multiple hours) I got it put back together and everything reconnected.
The car started after about 15 seconds of cranking, and immediately idled up to just over 3k.

Bad news: After starting, it stayed at 3k for a long time, then idled down and the idle started bouncing up and down around 1500. I've triple checked for loose hoses and connectors, and there is slack in both the throttle cable and cruise control cable.
Could a small leak at the new gasket between the UIM and LIM cause this? I cleaned both pretty well, especially so on the UIM. I didn't use any harsh abrasive that could have harmed the metal, but I did get a few tiny nicks into it with the razor blade, didn't seem like anything that would cause problems, especially not this much of one.

Videos:

https://streamable.com/k648bg

https://streamable.com/q4te9n

There is hot coolant flowing through the hose that runs to the UIM.

As for the in-tank pickup screen, it is rated for V12s, so I'm sure its probably fine, as far as flow rate goes.

Your 2nd video tells me everything I need to know; that's called "surging". Search on my name and that term and there are copious threads on what it is and how to fix it.

Here's what I think happened; your Fuel Injectors are now operating to spec. Over the years, you (*or someone) may have been making small adjustments to the Air Bleed Screw, the TPS, etc. to keep the idle steady as things deteriorated. Now that the culprit has been corrected (clogged Fuel Injectors), you're going to need to invest some time in getting everything back to normal again. The surging issues can be caused by many things, but usually - and with the age of our cars - it's due to galling between the aluminum throttle body and the steel throttle rods. This creates a feedback loop between incoming air, the TPS, and the Air Bleed system, sometimes also affected by the BACV getting in on the action if you have the A/C on or other electrical loads. Search and you shall find!

Also, I wouldn't worry about your UIM gasket install being the source of a vacuum leak. These aren't that big of gaskets and it's a straight forward install. Im sure its sealing just fine. Before you start taking things apart again, though - take a close look at your rubber vacuum hoses at the Dynamic Chamber. There are 4 at the front PS edge that go to the air distribution spider, 2 at the back PS edge that go to the Air Control Valve above the exhaust on the LIM, and then 2 more at the DS on and under the BACV that are easily forgotten, because they're hard to see. If every vacuum port is attached, then start in on fixing the surging.

If you get lost, post back, and Ill walk you through it first-hand. You've come so far, I feel like I owe you that! Great videos, by the way. I wish everyone could do that,...

Thanks for the info! I distinctly remembered only connecting one vacuum hose on the driver's side of the UIM. I forgot to connect the line that goes to the brass colored cylinder device mounted to the driver's side of the UIM.
Connecting this hose instantly solved the idle issue.

Image of the hose in question that looked connected at a glance but was not!

https://cimg5.ibsrv.net/gimg/www.rx7...298475fca2.jpg
https://cimg6.ibsrv.net/gimg/www.rx7...1c0fa6e89c.jpg


The car now runs and drive perfectly.
https://streamable.com/g304ia


Side note, but still related to the fuel system - When I backed into my garage, I noticed a high pitched whistling sound coming from the gas cap. After turning the engine off, I slowly opened the gas cap, and a lot of pressure came out. More than I've ever experience when opening any gas cap. I could hear the gas tank popping back into shape as the pressure was released. This is also the lowest I've ever run the gas tank in the car, the gas light came on as I was pulling back into the driveway. Is this amount of pressure normal? Is it caused by the new (Genuine Mazda) gas cap I just installed? The new cap looks different from the old one, and lacks the plastic thing in the center of the cap. This is the first time I've driven the car with this cap.


https://cimg4.ibsrv.net/gimg/www.rx7...f44ed989d4.jpg

SHE BANGS! SHE BANGS!!

Okay, great to see the car running so well. Your brights are on, btw. On the Fuel Cap, the new one you have is unvented and relies on the Charcoal Canister to purge the system. The old gas cap had a vent built into it. It's most likely that the vacuum lines between the Fuel Tank and the Charcoal Canister may be clogged. These are easy to check by disconnecting at the Charcoal Canister and attempting 5o blow air through them. There is a Vent Solenoid against the firewall that's supposed to open when the Throttle reaches above 2,500 RPM or so to suck the gas fumes stored in the Charcoal Canister into the intake to be burned. If you remove that hose and sniff around the Canister, you may smell the scent of gas, which is somewhat normal.

Emissions testing in my home state fails the car with an unvented gas cap, and it has to be manually passed by visual inspection for me to get new tags. Regardless, the only other vent is located at the "Roll-Over" valve under the car, between the tank and Fuel Filter which can also become clogged and prevent air passage. These rarely go bad, though. It's a beige plastic cylinder which has a few small vacuum lines going to it.

I'm also betting that if you fill the tank more fully, it won't build or retain much pressure, as there will be less air volume in the tank. If it doesn't bother you, I'd just fill it up and drive it. Nice work!

P.S. - that vacuum hose you missed goes to the Idle Compensator at the front of the BACV. It bumps up idle speed when electrical or power steering pump loads slow the idle speed, and it's controlled by the Air Solenoid located directly below it (*the 2nd from the left).

The brights are intentional, no one else was on the road and the headlights on this thing are so awful no one would noticed they were on even if there had been someone. I need to do an H4 upgrade.

I'll just switch back to my old fuel cap, I don't want my gas tank reenacting an East Palestine railroad tank car. I was able to blow air through the smaller hose on the charcoal canister that goes to the fuel tank. I was also able to blow air through the larger hose that seems to lead to near the oil filler neck. When blowing through this one, I could hear some valve opening after pressure built, and releasing the pressure. The service manual says the check and cut valve (I assume the thing you're calling the roll-over valve) should open at no more than 1psi, and it certainly felt like there was more than 1psi inside the gas tank.

Thanks for all the help! You're an encyclopedia of knowledge and your effort does not go unappreciated. Not sure I could have worked up the courage to take apart the intake manifold and fuel rail to fix this myself without help. Good to know that there are people out there with the knowledge and a willingness to help keep these increasingly obscure cars on the road.

This thread should be pretty much done, I just need to drop the gas tank and inspect it, clean and reseal if necessary. Removing the gas tank is another seemingly daunting task, but I suppose it really shouldn't be that bad. I'm just afraid of damaging any extremely rare connectors or bits in the process. Not sure if I'll get to that soon or not. I need to do it before more rust breaks free and clogs the fuel system up again.

This is my favorite thread of 2024! Great feedback, suggestions, and results.

Question for the group: would it be safe to run a cheap borescope into the (drained) gas tank?