OK, working on a 94 that just shuts off for no reason and will not start back up until it sits for about 30 min. I raised the hood and let it idle for about 15 min and it sounded great then just shut off, no stuttering or missing just off. I checked the icm and coil and neither were very hot but the coil wires seemed more wiggly than I see on most cars.

No engine codes and it almost starts on ether. It got dark on me before I pulled a plug and checked for spark, I'll do that in the morning. Any other ideas?

 

don't use ether on a GAS engine ! Starting fluid is/was designed for diesels...because they are built to take the very low octane of ether and the rattling it causes during its short explosive time. An OD of starting fluid can instantly bend a rod. It can also cause fires where it has collected and turned to liquid.

That's the kiss of death to aluminum pistons and standard rods/cranks.

IIWM, I'd be looking for a fuel pressure test gauge.
Plugged fuel filters do not set codes, they do not give warnings and they DO allow the engine to start and run again after sitting still for a few minutes so the crud in the filter or strainer can seep thru and reach the rail.

if there are NO codes, then look at the fuel system. Most ign problems will cause some type of code. A failing Opti might also be to blame. Your FSM has test procedures for that as well as fuel system.

 

Continue on your current course of action to determine if it is fuel or spark. Checking with a fuel pressure gauge would give you a direct result. I would also check for spark off the coil which I think is the easiest.

If it turns out to be a spark related problem, with these symptoms I tend to think of an ICM problem. They tend to just quit (on & off) when they feel like it as yours does. A test might not catch this, replacement may be the best troubleshooting direction in this case.

An opti tends to cause poor running with lots of different symptoms. If you did lose the low resolution pulse from the opti (error code 16 module 4), it would also affect the driving of the injectors since the pulse is the main clocking signal for all engine operation spark and fuel. You can monitor the injector pulse with a noid lamp and if you have the drive signal, then you can probably eliminate the opti.

There is also a procedure to check the drive to the ICM from the PCM. That would tell you if the ICM is getting the signal drive to operate. (It would also tell you if the opti and PCM were working OK). If it was there, then the ICM would look to be bad.

 

Pcolt,

do you remember the original electronic ignitions systems ?

Ford called theirs a "magic box". It was as Unreliable as the weather forecast. I had a new Ranchero that would find a way to just die and make me sit for a while. Most of the time when it was in the middle of the night, or a thunderstorm. Got to where I carried a new magic box around with me that I stored under the seat and plugged in as needed. One would act up then the other...POS system in the early days of elec ign. I hated it, so did everyone else. We were all buying points distributers to wire in our "evolving" engines of the time...(70s).

Certainly glad they improved over the years !

 

I would pull the ICM out and take it down to Napa to have it checked for free.

 

Can they detect an intermittent problem?

 

Yes I believe so, when I pulled the ICM there wasn't much thermal grease left showing and I thought that might be it but it turned out to be the ICM was failing.

 

OK, sun is out on this fabulous day so I went looked at the car again. No start again so I tried the hillbilly fuel pressure test and pressed on the test port with my fingernail. I got a tiny psst with a few drops and very little pressure. I turned on the key and the pump ran for the normal amount of time and I hopped out and checked pressure again. Seems like I got nothing. I can't even get a hiss from the Schrader valve.

 

Say never, give it a shot and get it tested. Something might show up. You might have some luck and find something. But if it checks good, it will still be suspect as defective.

Sure do. Also remember the oscillators in the electric ignition that destroyed you AM radio reception.

 

I cracked the fuel line coming out of the filter and had lots of pressure there but none at the rail. Could the regulator be cutting off flow?

 

A squirt is not a quantitative unit of measure. Pressure is about the same throughout the fuel system. Perhaps you did not depress the shredder valve hard enough. There had to be pressure there for the engine to run. You need a fuel pressure gauge, guessing does not count.

If you want to so you own work, a gauge is something you need and will have for a long time (like any other tool). You don’t often use it, but when you need it………

The FPR usually does not block the fuel from flow. It usually does not regulate correctly or leaks fuel back thru the vacuum line.

 

No squirt indicates no fuel at all. Now it is running fine again and the squirt goes to the firewall. I'm either getting plenty or nothing

 

Filter and/or pump w/strainer. Replace ALL together.

Don't be cheap here unless you don't mind doing all this again soon.

runs now. It'll die again. Plugged fuel systems are as intermittent a problem as it gets.


fuel pressure BEFORE the filter....
none after.


ummmmm?

You don't stand a chance without the FSM set, a fuel pressure test gauge, a cheap DVM, test lite, spark tester and noid lite.

THEN you can do diagnostics. Get the genuine GM paper clip as well.

 

Fuel Pump or ICM.

Follow procedures. Guessing leaves you stranded.

 

How does the ignition system and fuel system interact?

PO replaced all of the electronics and some of the connectors in an attempt to find this problem and it eluded him and he gave up and sold me the car.

 

Fuel and ignition are obviously separate systems but are related and controlled by voltage and engine computers. The ECM controls the ignition and also plays a part in keeping the fuel pump running.

I don’t know what this means. What electronics, need specifics.


There is a lot of interaction with computers (ECM & CCM) and systems in the car. Certain things are dependent on other things and many things have to happen first in sequence.

You say you have a drip from the shredder but have you ever checked for spark off the coil. Not knowing what to focus on will not give you the best direction. As said by me and others you need a pressure gauge plus other items as Leevset indicated. Help us help you.

We know you just got the car and don’t know how all the systems interact and believe me there is a lot. We all would like to help but without hard definite information accurate answers become best guesses.

I cracked the fuel line coming out of the filter and had lots of pressure there but none at the rail.
This is confusing as to whether there is fuel pressure or not.

Checking for spark should be an easier thing to do.

 

so, you're going to overlook the fact that your fuel filter or pump is failing?

ANY pressure in these rails should shoot gas all over YOU and the engine.
Heres another tidbit....that engine will start and run on 25-30 psi but it won't last long. As it starves for fuel it will buck and jerk, backfire, spit and die BUT it WILL try to idle on the remaining pressure until that's all gone.
It will die. After you wait for a bit, the fuel will again flow thru the clogged strainer or filter or the pump will run again (they stop when they get hot) and fill the rails under enough pressure to start and run again....for awhile.

How does the pump sound during the key-ON cycle? does it even come on?

You REALLY need to get the manuals so you can understand the complexity of the fuel/ignition system...and how the oil pressure effects it.

You can learn more about the health of the entire fuel system IF you know what to look for in the gauge behavior....but you need the gauge FIRST !

Without the tools...its just throwing parts. As the previous owner did foolishly. That cost him a good car.

Good luck, I know whats wrong with it. Hope you figer it out soon !

 

Of course in the midst of my diagnostic work the car started and ran for 30 min.

I guess I'll stick a new filter and a gauge on it and let it run until it quits again.

 

you may have too.. patience is your best friend!

 

Update sort of.....

I replaced the fuel filter today. Car started and ran for exactly 14 minutes before dying. When I tried to restart it the fuel pump and lights went crazy and the starter just clicked. I put the big charger on it but the battery measured 12.8 v. I checked spark and have none coming from the coil. I swapped the icm and coil with a known good setup and still nothing.

I think I have a short somewhere.

After sitting for about 2 hrs, I took the original coil/icm assy and put it in the freezer for an hour and stuck it back on the car. The car started right up and ran for 7 minutes this time before it quit with no restart. So, it quits with either icm on the car.

Another odd thing that happened after it quit the fuel pump ran for too long and the injectors went haywire clicking and I had no spark.