Can't resolve this no-fuel issue

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weba
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Can't resolve this no-fuel issue

Postby weba » Wed Sep 23, 2015 12:03 pm

So frustrated that I'm about to get my car crushed, I've battle with this for 3 weeks now and running out of ideas.
All started when I swapped in 'new' injectors to replace the ones I suspect leaking.

1992 3.1 V6

It has the following issue:
- Engine dies randomly, may sputter before. After it dies, can take several hours before it starts again
- Can run fine for hour, and then die, or die after one minute.
- When 'issue is on' it will crank just fine, and will start with spray can, but quit asap when I stop spraying

What I'm sure of:
- It's not the fuel pump (runs great, also tried hotwiring it)
- It's not the crank position sensor (ECM sees 250rpm when cranking)
- It's not the coils or ICM (there is spark)

What I'm pretty sure it is:
- There is no fuel spray from the injectors, meaning the injectors wont get the electricity they need.

- 12V+ is coming to the injector leads and ICM when measured with key on, that would lead the issue being ECM side (grounding of the fuel injectors, positive side is connected to the battery)
- Test light wont blink on the injector connector when cranking with issue on
- I've measured the resistance of the injectors and they were OK.

What I've done so far:
- Followed the factory manual troubleshooting guide to find the issue, it told me to replace ECM
- Replaced ECM
- Re-insulated all the wires in the injector harness in case of possible cracks
- Added new ground for the ECM <> body, to fuel injector driver wires, making sure grounding works
- Added jump-leads from ECM straight to injector harness to make sure it's not the wiring thats cutting the ground
- Tried other fuel pressure regulator
- Checked vacuum lines for damage

And yet, nothing works! =@

Here's the relevant page from factory manual:
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HELP! :Bravo:



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Re: Can't resolve this no-fuel issue

Postby Asylum » Wed Sep 23, 2015 12:17 pm

Simple question.

Is the fuel filter clogged?

Certainly sounds like the symptoms.


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Asylum Motorsports
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Re: Can't resolve this no-fuel issue

Postby SuperLbody » Wed Sep 23, 2015 12:22 pm

Are the injectors the correct replacements? Curious that it would run fine with the old but not work at all with new injectors. Verify they are the correct ones than get a fuel pressure test kit to verify your getting fuel pressure.



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Re: Can't resolve this no-fuel issue

Postby weba » Wed Sep 23, 2015 12:52 pm

Asylum, Haven't checked that yet, my experience is that clocking fuel filter wont affect idle, but high rpm. and this thing drives just fine until it dies.. May have to check that too to be sure, thanks.

SuperLbody, they came out of 2.8 and should be just the same.
I bought a fuel pressure gauge but it wont fit to my fuel rail, was meant for carb engines... to get a proper tool is overseas order and another 2 weeks. :(

I was just moving my car with starter motor only and it actually gave few chockes while at it, I'm now suspecting that this has something to do with massive drivetrain rotation issue i have with the mounting.. first step is to check engine ground.



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Re: Can't resolve this no-fuel issue

Postby weba » Wed Sep 23, 2015 1:11 pm

Wasn't the engine ground either, I have finger thick cables there...
Also, ALDL sensor data is all great, no error codes either



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Re: Can't resolve this no-fuel issue

Postby themixer » Wed Sep 23, 2015 3:32 pm

If the injectors are not firing it has to be either computer related or wiring related. for the sake of 3 wires run new ones even if its outside the car. did you try a new chip inside the ECM when it was replaced?



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Re: Can't resolve this no-fuel issue

Postby 1988GTU » Wed Sep 23, 2015 4:27 pm

Fuel pump relay or OPSU short circuiting?


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Re: Can't resolve this no-fuel issue

Postby ifixalot » Wed Sep 23, 2015 5:19 pm

If the injectors are not firing, the ECM has a flood clear mode. When you put the gas pedal all the way down, I assume it shuts off the injectors
to clear fuel from the engine.
If you have a short at the TPS or if you got the connector on wrong, (I don't know if thats possible), maybe the ECM thinks you have the gas pedal down to clear a flooded condition and so the injectors don't fire. Just a thought.



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Re: Can't resolve this no-fuel issue

Postby 3X00-Modified » Thu Sep 24, 2015 6:12 am

I was also going to say have you ohm'd the injectors when hot? I've seen one bad one kill a whole bank so if you happen to have two that act up when hot it could be killing the whole circuit.



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Re: Can't resolve this no-fuel issue

Postby weba » Thu Sep 24, 2015 8:15 am

themixer, already ran the 3 suspected wires. (both injector grounds and ECM ground). Also using custom-burnt own chips, but wont work with stock chip either.

1988GTU, fuel pump runs, also hotwired, so it's not the OPSU either.

ifixalot, "ECM will stay in clear flood mode as long as the throttle is 80% or higher and the RPMs are less than about 600." Well this can die at any rpm and any throttle position, also haven't noticed anything wrong in the sensor data, so I doubt it's that.

3X00-Modified, Haven't done that, for obvious reasons. Means pulling the upper intake and everything off to make that happen, but I could try that,
however both banks die together always,it never tries to run on 3...



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Re: Can't resolve this no-fuel issue

Postby ifixalot » Thu Sep 24, 2015 9:37 am

Have you ever watched the voltage off the alternator when this happens?
After we had an engine swap done on my daughter's Beretta,
she would hit the gas and the engine would bog.
It took awhile to discover the heavy wire from the alternator was pinched
and would occasionally short out causing the engine to stumble.
Maybe you drop below 12 volts intermittently from a short?



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Re: Can't resolve this no-fuel issue

Postby weba » Thu Sep 24, 2015 9:54 am

I just got raped by local parts dealer, fuel filter for 40 USD... #)%")%"!@£@[€

ifixalot, the voltage is fine. also remember that this issue can make the car immobile for several hours after it appears, and all that time the engine cranks great.



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Re: Can't resolve this no-fuel issue

Postby ifixalot » Thu Sep 24, 2015 10:17 am

If you haven't opened or installed it, I would take it back.
Can you blow through the old filter??
I doubt your filter is so clogged that it would not allow fuel to pass at idle or while cranking
and then all of a sudden it will pass enough to start the engine at times.
Since the engine ran better before swapping the injectors, I'd say something wasn't put back
together correctly. It seems like some intermittent electrical problem.



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Re: Can't resolve this no-fuel issue

Postby weba » Thu Sep 24, 2015 12:10 pm

Fuel filter did not help.

I installed 'injector light' to both banks on cylinders 1 an 6(?). and now it seems they are indeed blinking (dim) while cranking, so there may be some other issue. but last time I checked, there was spark at least.. HMmm



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Re: Can't resolve this no-fuel issue

Postby weba » Thu Sep 24, 2015 12:55 pm

I measured the 2 injectors I could without removing the intake, and after 2 minutes of engine running, other was 6 ohms and other 11.x

They were all close to 12 ohms before installing.

Seems like my replacement injectors may just be bad :(




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