Stalls while driving???[SOLVED]

[micbrody]

This seems to be heat related. Maybe a long shot, but easy fix.
Since it is a fuel issue, check the AFM terminals 39 and 36 (I believe they are the first two pins closest to front of car.
Check the resistance on these terminals. Take air filter off and use screw driver to keep air flap open. This should cause fuel pump contacts to touch each other in AFM. Resistance should be essentially zero. If there is any resistance, then the resistance will cause contact points in AFM to heat up, eventually not conducting circuit.........fuel pump shuts off.
If this is the case, a very easy fix, though you have to remove cover on AFM

[RRoller123]

+1

Still think this sounds like an AFM problem. If someone has a known good AFM they could temporarily swap in for him, that may finally answer it?

[76was124]

I don't quite understand. Does the timing light still activate while you are turning over the motor during a no-start condition??

If it does still spark, the next step I would take is to test if you have pulses firing the main injectors. All the main injectors fire at once so you would only need to test one of them. During a no start, disconnect the connector for one of the injectors and connect a noid light ($8 tester from the local auto parts store) or a volt meter. It probably would be easiest to have a helper hold the tester to the connector. You should then try starting the car and you should see pulses on the tester

If you do, then maybe putting an inline fuel pressure gauge is in order. I read a post where one member made the hoses long enough from the fuel rail to the gauge to tape the gauge on his windshield so he could see it while doing Test drives.

[76was124]

Remove duplicate post

[MarkKrieger]

Longtime lurker, rare poster here. I have owned a lot of 'classic' cars, some of them before they were classics, like my long-ago rusted out lovely 1972 Spider.

You said the only thing you changed over the winter was to add a battery cutoff. Some brands are notorious for your problem (I've seen this many times in one of the C2 Corvette forums). Remove the battery cutoff.

[micbrody]

If AFM fuel pump pins have little or no resistance when flap open, then check three other connections: The first would be check the double relay. Looking at schematic, this is what I would do:
1) unplug double relay
2) connect ohmmeter to 88y and 88c(or 88d). Resistance should be infinity
3) take 9 volt battery and energize 86b and 85 (use alligator lead clips on battery). When energized, the infinite resistance should change to zero resistance when relay activated. Like the AFM fuel contacts, if there is resistance, heat will be generated and eventually electrical contact with cease.

The other place to look is the inline fuse for fuel pump (I believe it is tucked way under dash to the left of steering column) I don't remember color of fuse holder (red? white?) . unscrew to inspect; clean contacts with file or dremel tool; clean with deoxy.

Lastly, ignition switch and/or its plastic harness could have bad connections/corrosion; though I would think the coil would have cut out.

[RRoller123]

As an easy alternate way of checking to see if the injectors are actually firing, you can use a mechanic's stethoscope, and very clearly hear them clicking on and off. Very simple and inexpensive. This will also tell you, even though a noid light will show that the signal is getting there, whether the injectors are indeed firing or not.

Pete

[ekstrandt]

So here is a few updates.
AriK
The no start is fairly short only about 10 seconds at the most. Yes the timing light will fire before during after stall and anytime I turn the key to start. Fuel injector is getting signal, confirmed with light. The light does not pulse its is steady on both connectors. Whether car is trying to start or when it is running(it fires up shortly after the stall).

MarkKreiger
Battery cutoff installed in Nov. ran great all winter. Is it something that "creeps" up a while after install? I will be trying it later today.

micbrody
AFM terminals work as you described, infinity then 0 when flap is moved. Heat is not a problem I can stall it before she ever gets warm. i just don't like to rev it that much cold, but i had to check.

I have connected fuel pressure gauge and got 32 psi idle, remove vacuum from pressure regulator and it goes to 40 psi. It will idle and run fine. When I start revving the engine to stall it and suddenly fuel pressure gauge maxes out 100 psi engine stalls. Pressure drops rapidly and then you can start it??? Pressure regulator? Why does it not fail at idle or during steady RPM only when I'm revving it up and down. Obstruction in return line? Is there a check valve in return fuel system that may be failing?

[micbrody]

There is a two way valve for fuel vapor that is located just before lines enter the trunk. (Round, gray, maybe about 1.5 inches in diameter) It vents gas tank to charcoal container of pressure builds too much in gas tank ; but also provides makeup air to gas tank from charcoal container.
Maybe a previous owner installed it on return fuel line that goes from fuel pressure regulator to gas tank

[ekstrandt]

Replaced fuel pressure regulator and it seems to be running fine now. Time will tell. Thanks for all the help and suggestions guys. That was a hard one as everything tested fine when running. Hope this helps someone else.

[AriK]

Great that you have it figured out

[76was124]

The light does not pulse its is steady on both connectors. ........I have connected fuel pressure gauge and got 32 psi idle,

Injector pulses are very short duration, and the injector turns on by the pulse grounding the one lead. I find it hard to see the noid lights flicker myself, so use and old school analog volt meter which shows the needle bounce a bit with pulses. Regardless, sounds like you narrowed down or hopefully solved the problem!!

Just out of curiosity, was the pressure guage on the supply side? And did you check the pressure after replacing the regulator?

[ekstrandt]

I had the fuel pressure gauge connected to the cold start injector hose. It was cold this morning so I had to reconnect cold start. I did not reconnect fuel pressure gauge after it ran fine. Do you think I need to?

[76was124]

Do you think I need to?

Not if everything is good...I was just curious