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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.
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:
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.
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.
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:
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.
Last edited by Augownage; 02-12-24 at 11:44 PM.
Reason: Added note about AFM door
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.
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,
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.
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?
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:
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.
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?
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;
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.
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.
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!
02-10-24, 11:35 PM
