masterprice33

Ahhh, man I don't know what to do. My 1985 corvette has a major stalling problem and I do not know what to do. I've been working with a mechanic I know and trying different things, like replacing fuel filter, fuel pump, fuel pump relay. The problem happens intermittently, but more so lately. Have performed fuel pressure tests, and at times when it dies, the pressure rapidly goes down to 0, other times it stays around 42 psi, which is also confusing. If anyone has ANY input, I've searched here and found a few things, but I'd like to know if anyone is familiar with this problem. It may not be relevant, but this problem started after I took my car in to have an oil change special and also get a diag test for codes as I had a service engine light on which I assumed to be the speed sensor, which it was, but had nothing to do with the stalling. The car was sitting outside for about 5 days as I was on a trip, when I came back and took the car off of the lot, the stalling problem started. I've heard solutions ranging from faulty ECM, fuel pump, bad ECM connection. I was wondering if the tinkering with the diagnostic connections would have anything to do with this. PLEASE ANYONE HELP ME I HAVEN'T BEEN ABLE TO DRIVE THIS FOR 3 MONTHS, the mechanic that is working with it has no clue at this point what to do. THANKS ANYONE, ask any questions that will help, and provide any solution if possible. I had posted a thread on this before and tried some of the things suggested to no avail. I'll put the link here.

http://forums.corvetteforum.com/show...ght=1985+stall

DESPERATE 85 OWNER, I need this baby for summer!

CentralCoaster

To be safe, check your wiring harness to the fuel pump, the insulation shrinks from heat and they can short out and cause intermittent faults.

You can actually test your fuel pump relay by hooking up a test light from ground to terminal G of the aldl port (lower left). If this light ever comes on while the car is running, it means the fuel pump isn't getting power from the relay or the relay isn't getting the computer signal. The car should still run though off the oil pressure switch.

FEDCBA
GHJKLM


I would also remove the fuel lid and rubber boot and check the harness under there.


Have you diagnosed the MAF as well?

86PACER

I know there's going to be people wondering WTF that means.

masterprice33

thank you for your input guys I'll have the mechanic at least try to check on these things, it seems like that could be the problem. Will let you know if this sheds any light into the problem. I was told it might be the MAF before so I bought a used but working MAF sensor and put that in and it does not solve the problem. Are there other components of the MAF that I should look at besides the MAF sensor? Should I be considering the MAFS module (If that is separate from the MAF sensor) I'm not a mechanic by any means, have learned more from this site than I have in my whole life haha, so detailed descriptions and help would be nice

rick lambert

Because of the loss in fuel pressure, and having already installed a new fuel pump, I think you either have a bad fuel pressure regulator or bad injectors. Have your mechanic pull the hose off the regulator..if he sees gas in it..bad regulator. I'd also have him ohm the injectors..both hot and cold, my bets on bad injector(s).

vette_tweak

I agree with Rick... That may explain why you sometimes have 0 PSI or 42 PSI FP when it stalls...if the injector intermittently sticks open, it could cause the engine to stall and the FP may read 0. I'd connect the FP gauge, turn the key until you hear the pump (without starting the motor). The FP should rise up to 42 or just below depending on the condition of the battery. If it does but quickly falls, you have a leak in the system...could be an injector or the regulator.

masterprice33

thanks again will have the mechanic check these out, I actually did buy a new FPR but he hasn't touched it yet so we'll see. will get back once he's tried this.

masterprice33

may erd

Fasterer

When my 85 pump went I made replaced it with one from Advanced. The replacement gave me more problems and the replacement for the replacement was no better. I finally spent the bucks at dealer and immediatly had 40 lbs pressure. The muffler/vibration damper/connecter that connects the pump to the fuel line could also cause problems.
But have you checked for any new codes. if not disconnect the ecm fuse or disconnect the battery to clear history and then restart car. When it stalls a couple times check for any codes. Also when it stalls can you actually see 42 lbs on fuel guage as engine quits? If you hold throttle above idle it continues to run? Is it same when engine is hot or cold? I read your other posts and before the speed sensor and dealer pulling codes the car ran fine?? This satrted as soon as you left dealership??

masterprice33

To answer all of your questions as best I can...
When it stalls, it either remains at 40 psi or drops rapidly to 0 on the fuel gauge, more often it stays at 40 psi. I'm pretty sure that open throttle no idle it has not stalled on me, the stalling happens either at idle or between the time of the end of acceleration and stopping. Hot or cold it doesn't seem to make a difference, but the car has had a harder time starting now since all this has happened, longer time to crank, multiple times to crank, etc. and YES, before the dealership pulled the codes and checked for the speed sensor the car was not stalling, so it makes me wonder what they could have done to make this happen, perhaps jar something loose, bust a fuel system component, mess with the ECM connection, i don't know. still open to anyone elses suggestions

Fasterer

Have you checked for any current trouble codes. I would do that next. IF you have no codes and it stalls with 40 lbs of fuel showing on the pressure guage i would verify spark next. You could use a timing light that uses induction and hook it up and watch the firing of one plug to see if ignition goes dead.

masterprice33

addressing another question you asked, the problem does NOT happen when accelerating, but happens when cruising at a constant speed or at idle, has stalled even at around 50 mph constant speed.

rick lambert

Have your mechanic ohm the injectors...both hot and cold. I'm thinking sticky injector(s) seems if it were the Fuel pressure regulator the pressure would drop all the time.You may even want him to check the pulsing of the injectors with a noid light.

masterprice33

we once checked the pulsing of the injectors by just feeling them, and 1 of them we could not feel a pulse and another was faint.

masterprice33

please if someone could advise on my last reply that would be great

LD85

Forgive me for not reading hte entire post, but my 85 did this and it was the HEI, put in a new HEI module and it never happened again.

I would be driving along and the car would die, or rollling to light an the car would die.

They only cost @ 40 bucks or so, it is worth it if you have not done so already.

rick lambert

Your mechanic should be using a noid light to check the injectors for pulse (signal).And you can have the ignition module LD85 was referring to checked at any Autozone store.

86Pacecar

I've had this problem before and the module would only fail once warmed up. Took it to my local NAPA and had it checked and it would fail rather quickly. Put a new one in and no more problems. Good luck with the repair, intermittants are a PITA.

MR NICE

check for gas in the oil

LD85

status