RX7Club.com - Mazda RX7 Forum

RX7Club.com - Mazda RX7 Forum (https://www.rx7club.com/)
-   2nd Gen General Discussion (https://www.rx7club.com/2nd-gen-general-discussion-323/)
-   -   Cant start my fc (https://www.rx7club.com/2nd-gen-general-discussion-323/cant-start-my-fc-1155089/)

Bravo928 01-02-22 09:05 PM

Cant start my fc
 
Can someone please help ? Engine cranks over there is spark and fuel... i remove the plugs and they are wet with fuel.. is it my injectors my dampner or fuel pressure reg
the injector are stock and when i tested with multi meter only the trailing inj. Read of 2.6 ohm. The other two go all crazy up and down on the meter...
i took apart the intake manifold disassemble the fuel rail with injectors and connected them to the the fuel line without the manifold. I bridged the yellow plug on passenger side of engine bay so pump runs as soon as u open ignition switch and when i turned the key fuel started leaking from the inlet line that connects next to the pulse dampner. The fuel line is good no hole or breaks..

mazdaverx713b 01-03-22 05:53 AM

You're all over the map with this one. First and foremost, wet spark plugs mean that the engine is flooded. Deflood the engine properly and clean and reinstall the spark plugs. That should have been your first step, as you stated that you have good spark.

Next, since you took the injectors out, I recommend replacing the injector o-rings and seals. If you have a leak at the inlet line, check the feed hose for a split or hole and check to make sure the pulsation dampner is not leaking. Get the fuel leaks buttoned up and we can go from there with helping you get the engine started.

Bravo928 01-03-22 08:23 AM

Okay i will do that.. before i took the manifold out there was a small leak from the damperr. And also i did remove the plugs and let them dry. I bridged the yellow connector in the engine bay so the pump ran constantly and cranked the engine without the egi fuse so it wouldn't inject fuel and let the excess fuel out but there was fuel still being injected .
it stopped once i remove the wire that was bridging the pump.. is that normal?

mazdaverx713b 01-04-22 05:44 AM

You do not want to jump the terminals in the yellow fuel pump test connector when deflooding the engine. You want to remove all chances of fuel being injected into the engine when deflooding.

The pulsatidampner reduced injector pulse noise and is a common leak point. Its recommended to replace it any time you have it out. People have lost cars to fires because of it leaking. While its apart, I recommend replacing it.

While the spark plugs are out, check the electrode for wear. You never said how old the plugs were and having good spark plugs is critical. The spark plugs should be different. You should have two NGK BR7ET and two BR9ET spark plugs if I remember correctly. Ensurebthe electrode is squared at the top and that its nice and tall. As these plugs wear, the electrode shrinks and wears almost to a small point.

Bravo928 01-04-22 09:21 AM

Well i just looked at the plugs u mentioned and they arent even close to what i have on there. Its a long story as to why i have the plugs i have. thank u for that i will correct it.The ones i have on have four of those hook looking things.. u cant even see the center part..

mazdaverx713b 01-05-22 06:02 AM

Sounds like you have NGK BR8EQ-14 spark plugs. Those are meant for the 81-85 RX-7. I would go to the parts store and order the correct set of plugs. After work tonight I'll post a picture of what the correct plugs look like.

Bravo928 01-05-22 09:06 AM

I removed them yesterday and they are all 9's all trailing plugs. Will that cause the car not to start?

mazdaverx713b 01-06-22 05:52 AM

Having all trailing plugs will not cause the car not to start. I've bought cars this way that were running. Running poorly but running. Recently I had an RX-8 come in with four trailing plugs. I don't understand why people just don't put the right plugs in.

Bravo928 01-08-22 08:45 PM

Im doing a spray test tomorrow. What should i be looking for? After that im replacing bad ones if any and replacing all the rubbers on the good injecyors also if any..
am i going to need special tools for what i just mentioned.
if so what kind...
I bought new fuel to replace the old one

mazdaverx713b 01-09-22 12:03 PM

How are you performing a spray test? You will need a way to pressurize the injectors and a way to pulse them when under pressure.

I have an injector pulse tester that I use that works great and I have a special adapter for injectors that pressurized them one at a time and feeds in a cleaning solution. Its something I made. It works well but you will need somethinsothat does something similar.

Bravo928 01-14-22 09:16 AM

I did the spray test on the injector that make the multimeter go hay wire. And it sprays should i replace it anyway?
i did the spray test by adapting the injector to some pieces of a fuel pressure test kit. And on the other end was a can of carb cleaner..

Bravo928 02-25-22 11:38 PM

https://cimg1.ibsrv.net/gimg/www.rx7...f99796f7aa.jpg
What are these called? I should probably replace the o rings on them right?

DR_Knight 03-03-22 04:15 PM


Originally Posted by Bravo928 (Post 12507893)
https://cimg1.ibsrv.net/gimg/www.rx7...f99796f7aa.jpg
What are these called? I should probably replace the o rings on them right?

fuel injector air bleeds. Looks like from the secondary injectors. Mazdatrix has them in stock.

and yes might as well put new orings. I’ve never had to replace the actual air bleed part, a bit overpriced for what they are.

Bravo928 03-06-22 05:53 PM

https://cimg6.ibsrv.net/gimg/www.rx7...8f1b4508e1.jpg
https://cimg0.ibsrv.net/gimg/www.rx7...9f7aeaed85.jpg
This thing goes to the shaft sensor but has a wire that is connected to nothing but is connected to something in tbe other end. Which is sjown on yhe other pic. Previous owners messed with it . My vocabulary is limited when it comes to cars otherwise i would elaborate more . Please help

Brrraaap 03-22-22 05:27 PM

Try to locate where that wire goes in the service manual, that could be one of your issues.

Bravo928 03-29-22 02:56 PM

Can i find that online? Or do i have to go buy one?

Brrraaap 03-29-22 06:18 PM

https://rotaryheads.com/PDF/2nd_gen/ this should be it, it can be found in the FAQ section I belive

WondrousBread 03-29-22 09:49 PM

Don't connect that wire to anything other than at the existing crimp connection.

The single braided wire with no insulation is a shield for the crank angle sensor. This shield is supposed to be grounded at the ECU side, and not grounded at the CAS side. You can check the connection by turning a multimeter to the resistance setting and holding one probe to the shield and the other to a bolt on the body. It should read zero or nearly zero.

If you ground that at the CAS end it will no longer work as intended and allow noise into the crank sensor signal. Worse, connecting it to something else could cause a short.

The way it's supposed to work is that the silver braid wraps around the four wires for the CAS. Then all those wires are sleeved in grey plastic insulation. In your case it looks like they'vr been peeled away, so if possible I would wrap the four wires with the shield and then use a piece of electrical tape to secure it at the CAS side. Then wrap the whole thing with harness tape.

The other photo where it's crimped to the harness is probably the factory connection where it goes from shield to a ground wire, terminating at one of the four ECU grounds. I have never tried peeling that part of the harness back but it looks like a factory crimp.

Bravo928 03-31-22 02:27 PM

I want to first thank all of u on this thread. I appreciate ur time and help. I'll make sure to patch up that braided wire. I was putting in a relay under the glove compartment and found some wires that dont look like they are factory crimped. Ill be turning my e mail notifications on. Once again tha
https://cimg0.ibsrv.net/gimg/www.rx7...4cdb656b88.jpg
nk u guys for ur time

Bravo928 04-11-22 10:57 AM


Originally Posted by WondrousBread (Post 12512294)
Don't connect that wire to anything other than at the existing crimp connection.

The single braided wire with no insulation is a shield for the crank angle sensor. This shield is supposed to be grounded at the ECU side, and not grounded at the CAS side. You can check the connection by turning a multimeter to the resistance setting and holding one probe to the shield and the other to a bolt on the body. It should read zero or nearly zero.

If you ground that at the CAS end it will no longer work as intended and allow noise into the crank sensor signal. Worse, connecting it to something else could cause a short.

The way it's supposed to work is that the silver braid wraps around the four wires for the CAS. Then all those wires are sleeved in grey plastic insulation. In your case it looks like they'vr been peeled away, so if possible I would wrap the four wires with the shield and then use a piece of electrical tape to secure it at the CAS side. Then wrap the whole thing with harness tape.

The other photo where it's crimped to the harness is probably the factory connection where it goes from shield to a ground wire, terminating at one of the four ECU grounds. I have never tried peeling that part of the harness back but it looks like a factory crimp.

thank u 4 ur help. Its much appreciated.. well it turns out that my ecu has a few mods. If u want to call it that.
there are two pressure boost sensors or watever they are called. One where it should be and the second one on passenger side kick panel. They are spliced to the same wires except for one. Is this normal or no?

WondrousBread 04-11-22 11:16 AM


Originally Posted by Bravo928 (Post 12513776)
thank u 4 ur help. Its much appreciated.. well it turns out that my ecu has a few mods. If u want to call it that.
there are two pressure boost sensors or watever they are called. One where it should be and the second one on passenger side kick panel. They are spliced to the same wires except for one. Is this normal or no?

I'll preface this by saying I don't really know how those two sensors interact with the ECU because I've never dug into it. Both mine test out fine. If I unplug the engine bay one, not much happens. If I unplug the kick panel one, the engine runs terribly. That's the extent of my knowledge on the topic, so the following is speculation:

I believe both of those sensors are the three wire type. Meaning they have a +5V terminal, a GND terminal, and a signal terminal. The way this works is the ECU compares the output voltage against the 5V reference voltage to determine the reading. You can see a complete pinout and some other diagnostic info here:

https://www.rx7club.com/2nd-generati.../#&gid=1&pid=1

I wrote that for a different purpose, but the first spreadsheet and the included FSM pages may be of use to you. Anyways, this is a roundabout way of saying that two terminals being shared between those sensors is not unusual, and I believe you'll also find that the 5V splice ends up at the TPS and MAF. Same for GND. As for whether those are factory crimps, I don't know. The factory used little brass crimps that were uninsulated, then wrapped them with electrical tape before wrapping the whole harness.

Looping back to the original issue, an engine needs four things to run: Air Fuel Spark Compression. I listed these in order of severity and ease of diagnosis.

- You have air if the intake is unobstructed. Make sure the MAF is plugged in, and that there is nothing under the filter. Make sure the MAF door moves freely.

- You should have fuel because the plugs are wet.

- Spark can be checked using a spark checker. They're cheap and very easy to use. If you have a timing gun that works too, and doubles to let you check timing (although it is unlikely to be incorrect unless you've altered it).

- A compression test is simple too, at least to get a ballpark estimate. Take a normal compression tester, look down the bore of the threaded end that goes into the spark plug hole, and remove the little valve. Install into the spark plug hole (I think it's supposed to be trailing, really it isn't critical for an estimate). Pull out EGI fuse. Have friend floor gas pedal and crank car while you watch the gauge. You need three even bounces above 90psi or so at a minimum. Repeat for rear rotor.

Also, check the green sensor at the back of the water pump housing (directly below alternator). Make sure it's plugged in firmly. Having wet plugs implies that you have a spark issue, but this sensor controls cold start enrichment and can cause a no-start.

If you follow the above steps, you should find the issue. I know in real life it isn't always that simple but this is a good starting point. If you have all four of the above things, it may run like crap, but it should at least run.

Bravo928 04-11-22 02:01 PM


Originally Posted by WondrousBread (Post 12513783)
I'll preface this by saying I don't really know how those two sensors interact with the ECU because I've never dug into it. Both mine test out fine. If I unplug the engine bay one, not much happens. If I unplug the kick panel one, the engine runs terribly. That's the extent of my knowledge on the topic, so the following is speculation:

I believe both of those sensors are the three wire type. Meaning they have a +5V terminal, a GND terminal, and a signal terminal. The way this works is the ECU compares the output voltage against the 5V reference voltage to determine the reading. You can see a complete pinout and some other diagnostic info here:

https://www.rx7club.com/2nd-generati.../#&gid=1&pid=1

I wrote that for a different purpose, but the first spreadsheet and the included FSM pages may be of use to you. Anyways, this is a roundabout way of saying that two terminals being shared between those sensors is not unusual, and I believe you'll also find that the 5V splice ends up at the TPS and MAF. Same for GND. As for whether those are factory crimps, I don't know. The factory used little brass crimps that were uninsulated, then wrapped them with electrical tape before wrapping the whole harness.

Looping back to the original issue, an engine needs four things to run: Air Fuel Spark Compression. I listed these in order of severity and ease of diagnosis.

- You have air if the intake is unobstructed. Make sure the MAF is plugged in, and that there is nothing under the filter. Make sure the MAF door moves freely.

- You should have fuel because the plugs are wet.

- Spark can be checked using a spark checker. They're cheap and very easy to use. If you have a timing gun that works too, and doubles to let you check timing (although it is unlikely to be incorrect unless you've altered it).

- A compression test is simple too, at least to get a ballpark estimate. Take a normal compression tester, look down the bore of the threaded end that goes into the spark plug hole, and remove the little valve. Install into the spark plug hole (I think it's supposed to be trailing, really it isn't critical for an estimate). Pull out EGI fuse. Have friend floor gas pedal and crank car while you watch the gauge. You need three even bounces above 90psi or so at a minimum. Repeat for rear rotor.

Also, check the green sensor at the back of the water pump housing (directly below alternator). Make sure it's plugged in firmly. Having wet plugs implies that you have a spark issue, but this sensor controls cold start enrichment and can cause a no-start.

If you follow the above steps, you should find the issue. I know in real life it isn't always that simple but this is a good starting point. If you have all four of the above things, it may run like crap, but it should at least run.

https://cimg3.ibsrv.net/gimg/www.rx7...8203528aee.jpg
Those are the plugs for boost pressure sensor. Thanks for the link very helpful .. Ill post once i make progress One other ?... The resistor pack has to have continuity on all 5 prongs? I ask cuz i read that low imp. Inj. Have to have that resistor and high imp. Inj. U can just bypass it by splicing all the wires. So im assuming that there shouldn't be continuity an all prongs. Im i on the right track?

WondrousBread 04-11-22 02:06 PM


Originally Posted by Bravo928 (Post 12513813)
The resistor pack has to have continuity on all 5 prongs? I ask cuz i read that low imp. Inj. Have to have that resistor and high imp. Inj. U can just bypass it by splicing all the wires. So im assuming that there shouldn't be continuity an all prongs. Im i on the right track?

I don't know exactly, but there is a test procedure. It's in the factory service manual at Foxed.ca, in the fuel and emissions section. Take a look and it will show you which pins should have which resistances.

Bravo928 04-11-22 06:50 PM


Originally Posted by WondrousBread (Post 12513816)
I don't know exactly, but there is a test procedure. It's in the factory service manual at Foxed.ca, in the fuel and emissions section. Take a look and it will show you which pins should have which resistances.

ill check it out... on ur spreadsheet on pin 2c its labled black for ground on my harness its a brown black wire is that wat u ment? And pin 2o and 2p are not connected at all they end at a green connector on passenger strut tower. I still havent checked what those solenoids are connected to.

WondrousBread 04-11-22 06:55 PM


Originally Posted by Bravo928 (Post 12513856)
ill check it out... on ur spreadsheet on pin 2c its labled black for ground on my harness its a brown black wire is that wat u ment? And pin 2o and 2p are not connected at all they end at a green connector on passenger strut tower. I still havent checked what those solenoids are connected to.

So, 2O and 2P end at the green connector for a different reason. That's the TPS check connector, and when you plug two lamps into those pins (third is gnd I think) it tells you what the ECU is seeing from the TPS. Keep in mind these cars are from before check engine lights and standardized error codes. Those wires will also likely be plugged into those solenoids on the rats nest, and then spliced somewhere in the harness. Unless it's been messed with.

2C is black on my car, but I wouldn't worry if it isn't. As long as it's a ground.

Regardless, I would start with the diagnostic steps I mentioned first before digging into the ECU. I know you have some wiring weirdness going on from the previous owner, but 99% of engine problems will be solved using those steps. For example, none of those solenoids are required for startup.

It's possible the PO messed up some wiring, but way more likely that it's something simple. Just my $0.02.


All times are GMT -5. The time now is 09:53 PM.


© 2024 MH Sub I, LLC dba Internet Brands