1985 CONFUSING STALLING problem
 

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!

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?

I know there's going to be people wondering WTF that means.
http://img83.imageshack.us/img83/303...nnector7ec.gif

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 :)

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).

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.

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.

may erd

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??

Response to Fasterer
 

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.:crazy: :eek: still open to anyone elses suggestions

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.

reply to fasterer
 

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.

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.

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.

help?
 

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

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.

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.

:iagree: 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.

check for gas in the oil

status:bigears

Have you checked for any service codes. You can do it your self with a paper clip and it might just point you in the right direction.

sorry everyone i've been on vacation for a couple of days, just got back and have seen your replies. This is the first time someone has suggested the HEI module, we don't have an AutoZone here hopefully Kragen or Napa will do it for free. How do you check for codes with a paper clip? If you could just lay out the steps for me here that would be awesome. Thanks again guys, the mechanic I'm working with is stupid I'm beginning to think, I'm sending him lots of information and he's slackin big time, I have to see if he worked on the injector stuff over the weekend, grrrrrrrrrrr. Oh, with the HEI module, what would ALL the symptoms be for a failed module, just basically what I've described? Does that account for the random drops in fuel pressure also?

I've had ignition modules that tested fine, but failed when warm on the car.:yesnod: There is really no way to test it aside from putting it in the oven right beforehand. By the time I would go through the diagnostic steps over again, it would cool down enough to work.

to central coaster
 

do you have any suggestions for me on what to do? just real frustrated with this whole process, i don't want to fork all the dough over for one of the so called high quality shops to mess something up again.

Go down to Autozone etc, buy an HEI module @ $40, take the distributor cap off, put the HEI module in and put the cap back on.

:iagree: Had similar issue with car - module cured it!!!

One of the reasons they run the ignition module through at least ten cycles is so that it gets hot, less than ten, you just don't know.But it's still the FP drop that brings me back to injectors,fuel pump or regulator.

what about the times that the car stalls without the fuel pressure dropping down? what would that lead you to believe?

The fuel pressure thing is a little wierd. However you stated that your mechanic is stupid and maybe he just wasn't remembering things correctly or the guage was bad. From what you describe it could be a number of things but if it doesn't happen till it's warm the HEI module is a likely culprit. NAPA will have the tester and part and will test it for free or at least should test it for free. It isn't a difficult repair and you could probably do it yourself but if your "stupid" mechanic does it make sure when he puts the new one in he uses the proper heat transfer grease(should come with the new module) so you don't cook your new one right away. The part will cost a bit more at NAPA than Autozone but I've found my local NAPA electrical parts to be the best. Without seeing your car we are just giving you some educated guesses but the guys here have given you some solid advice. Good luck and keep us posted as to the results.:thumbs:

well about the FP readings I personally witnessed them happen that way, and the gauge is a brand new Hypertech. It doesn't seem to happen. It's kinda weird, but when the problem FIRST started I could start the car just fine when it was cold and it would run fine, and then randomly down the road somewhere it would stall out, then it would either start right back up or take longer to start up, but it would in fact start up. Later on, it would start up fine cold and then eventually when it would stall, it would become increasingly hard to start, and even got to the point where it would not start at all, it would crank and crank, and the crank would get weaker and weaker, until it would not crank at all. Now at this point, even when cold and sitting for a couple days it will take forever to get the car even started and when sitting in idle without even driving it it would stall out, and either the FP would stay around 40 psi or would drop rapidly. How likely could this problem be coming from a bad computer or a bad ground? How would I check for a bad ground?

I agree with coil or spark module inside the distributor overheating.

Have you checked spark during the stalled out condition? My guess is still the module. The fuel pressure drop from how you describe it seems to happen after the car stalls which points to spark, however if it dropped rapidly causing the car to stall I would continue looking at the fuel system. At this point it is your chice to throw parts at it but the module is not that expensive.

I'm going with most on here and say the ignition module. As you say it only gives you most trouble when it's hot. I'm sure you mechanic has checked for spark. The fuel pressure is a little strange because it usually either drops or holds. The injectors need to be ohmed and a leak test done on. Your mechanic needs a process of elimination. I usually will start with fuel, then spark, then air/sensors ....that is if no codes. You will need the ignition module tested and most places will do it for free. I also wonder about the fuel pump/relay wiring.

reply to 86Pacecar's suggestions
 

When the fuel pressure dropped rapidly, it happened AFTER the car stalled, and then at other times when it would stall the FP would hold at 40. So from what you are saying this points to a spark problem, meaning the ignition module? Again thanks everyone for the input it's helping me out a lot, just wish the mechanic would make the time to perform some of these tests!!! ahhh man I need to have a corvette guy in this town but there is none, unless any of you know a corvette guy in the Humboldt County area in northern California....

With that explaination of the fuel pressure it definately sounds like the module is getting hot and failing. It's a very likely culprit and you can do this rather easily.:thumbs:

thanks guys I'm really hoping that the module will cure the problem.

Thegood part is that you can change thisout in less than 20 - minutes.:cheers:

that's good to know, i'll remember that if my mechanic ever says, umm yeah that took about a couple hours :nono:

as a test, hot wire the fuel pump 'on',
see if anything changes.

Do you know anyone that would loan you a ecm for test purposes I have seen several cases that one would cause the problems you are describing and not throw 1 code I even have had one go bad and lock the injectors open,with no code.Also I have had one have a bad fuel pump relay and a oil sending unit go flakey at the same time.
(From experiences I have had ):thumbs:

in response to mr. kidd........I do not have access to a good ECM to test with, we replaced the fuel pump relay already, had no effect. One thing I thought was rather peculiar was that the mechanic noted that the fuel pump fuse was blown before, and when he put a new one in there it also blew eventually. But even with a new one in now it is still having the same problems, according to my mechanic. Does this lead any of you to change your opinions on what's going on? And what exactly would the oil sending unit have to do with these problems? is it pricey to replace?

Have the mechanic run a hot wire from the + battery to terminal G of the ALDL. It should run the pump continiously until the wire is removed. You might have a short in the tank, connector, or anywhere inbetween the fuse and the pump.

another question.....could any of these specific symptoms i've described have to do with messed up oxygen sensors or a bad catalytic converter?....I can't get a hold of the mechanic so until then I can't give an update.

I didn't see in any of your posts that the O2 sensor or cat would be the problem. A clogged cat will usually glow when hot and make your car feel like there is no hp when giving throttle, but not stall unless it is completely blocked. If completely blocked it probably wouldn't start, kinda like a potato in the muffler type thing. The O2 sensor doesn't start sending signal until the exhaust temp reaches 600* and/or the engine temp reaches 140*. With a faulty O2 sensor it will make the car run rough and either tell the ECM to add more or less fuel, associated with rich or lean exhaust smell and exhaust color. The O2 sensor can be tested for volts....ranges from .1v lean to .9v rich. The numbers will vary every second depending on engine load. Did you get the ignition module tested yet? More things would be to check the color and smell of the spark plugs and ohm the wires.

a little update here........I will be definitely getting the module checked tomorrow, another thing I wasn't aware of until now was that at its CURRENT state, when I got together with the mechanic, the fuel pump WILL NOT turn on with the ignition key on 'ON', at least that's what happened today. I swear this is getting crazy. At least after I get the module checked we can eliminate one of the things many on here think would be the problem. The wiring is all jacked up in the car I swear, but still I got this car a couple years ago and it hadn't ever continuously and intermittently stalled like this until after I brought it into the shop and had oil change done, codes checked, and had the radiator replaced. I forgot to mention RRTvette's advice about seeing if the pump would run with a hot wire from the battery to ALDL port G to the mechanic, I think I'll tell him tomorrow to do that and then I'll report back

Progress!!!
 

PROGRESSS!!!, I just had the ignition module tested at Napa and, after the first run the guy there said it passed, but once hot, started failing over and over, so we may have our culprit. I will write another post once I have the mechanic put the new module in and see what's happening from there.

I guess I was lucky, the mechancs I took my car too, when I first got my 85,, told me straight away, its the HEI,,, and he was correct.

I could be driving along & depress the clutch and the car would die, turn it on, then die, let it cool for a bit, then it was OK.:crazy:

update.....well we THOUGHT the ignition module cured everything, it only made it better, now it will stall less often, and after stall it will start RIGHT back up, so I'm thinking there were a couple of problems. So the stall is still there. Upon stall fuel pressure maintained, so at a loss here once again, advice anyone?

O.K. you fixed one part that was bad...good. Now describe what it is doing all over again. If fuel pressure builts and holds then the pump is probably good. Have you checked the spark plugs and/or PVC?

I hope your mechanic is using a factory service manual or Helms manual. I'm thinking he should be checking the voltage at the TPS=throttle postition sensor.Accoding to the FSM, this is one of the most important sensors on our cars!

Ok, i'm back from Redding CA to report what happened the other day with the installation of the ignition module. So before the new one was installed, the car would have a hard time starting, and even when it did turn over, it would stall in park/idle pretty quickly, and every start thereafter took longer and longer, until eventually not being able to start at all. So after seeing that the old ignition module was bad, we replaced it with the brand new one. Although it took awhile to start and actually died rather quickly (mechanic says he 'thinks' he saw the check engine light come on right before it died), we tried it again and it started right up and held good strong idle for quite some time, shifting from park to drive and back and forth, idle held very well for about 5 minutes, so we decided to take it for a drive...

Drove it around pretty good for about 10 minutes around time, everything seemed back to a no stall condition, at idle, cruise, acceleration...So we bring it back to the shop and let it idle for awhile. Idle was still holding very well, engine was all warmed up. Then....as I almost expected to happen, it died. When we tried to start it back up it started up RIGHT away, good strong start, but the idle seemed a tad jumpy on this go round, and then it died again a minute later, but would start right back up quickly. The thing is...sorry this is taking so long I must explain everything here....This was the problem IN THE FIRST PLACE, I believe the ignition module actually failed maybe a few days AFTER, as my car overheated because my radiator went out, which I have since replaced, which is why the problem appeared to be getting worse, so now its back to the beginning. So there it is RRTvette, if you have any more questions, let me know....I'll have to have the mechanic check that TPS voltage and maybe the code that the first stall may have created. Mechanic was wondering what types of things make an ignition module go bad...

To Rick Lambert
 

Mechanic is not using an FSM, just the Haynes manual, I know I should get the FSM I was hoping I wouldn't have to but it seems like a GREAT idea now. I'll have to see about the TPS tonight and see if he can test it tomorrow.

Well you seem to have this problem only after it warms up. The SES light came on but does it stay on? If you try and pull the codes it might not show up if the SES light isn't on. I would try and put a fuel pressure guage on while driving and at idle hot to see if there is any drop in pressure causing this...to rule out fuel problems. When it stalls the pressure should hold between 36-40 psi and not drop much at all. It seems to crank back up everytime when hot so the new ignition module should be o.k. I know this is an aggravating situation for you. Could be so many things, so the only other thing I can think of besides guessing, is to run a scan on the car until it happens again to see what the ECM is seeing.

The SES light does not stay on, and it only came on right before the FIRST stall RIGHT after we installed the ignition module, and it did not stay on. After the ignition module was replaced and we drove it around awhile, then stalled, there was no SES light on before it stalled. We checked the fuel pressure right after it stalled and the fuel pressure remained constant at around 40 psi. We have not noticed drops in fuel pressure BEFORE any of the stalls we noticed during all this time when working with the vette. Like I said in the past, there were a few odd times when the fuel pressure would drop very fast, but this did not happen very often, and it hasn't happened since placing the new ignition module in. Thanks for your help I really appreciate it everyone.

I have to ask if the mechanic installed the ignition module properly with the proper heat transfer grease between the module and the distributor. If the grese is not applied correctly it will not transfer heat properly away from the module and it will heat up and quickly start to fail again. This sounds like what is happening, and it is a common misstep when the module is replaced. My money is still on the module, but hey I'm a long ways away and cannot see what is happening.
Seems too coincidental that it ran good for awhile after the module was replaced and that it has now gotten back to the same point. Not unheard of for a new part to fail even if installed correctly.

One other possibility on this, I've had a HEI that acted exactly like it had a bad module, but it turned out to have a bad wire on the inductive pick up (the little, round, pointed (kinda like a throwing star, but shorter points) star looking thing down below the module. You may havew to remove a plate in the base of the Dist. to see this, can't remember for sure right now. I know if you have to change it, you have to drive out the roll pin that holds the gear on the bottom of the Dist. on, and then knock out the shaft to change it (you've pretty much got to dissassemble the complete Dist. to change it), or you can just order a performance Hei Dist. with a better than stock module, etc... for Summit for about $130.00. Before you do that though, make sure you've traced the problem to the Dist.

I personally watched him do everything with the transfer grease on the ignition module, and he was very careful about it, so I doubt it was installed incorrectly. In response to Blownfuel1, it was proven that the old module was in fact failing, as I had it tested at Napa. Will report back when I can rule out the TPS, that's my next move, if that doesn't do it I'll look back at the module

I just received a message from another member saying that he strongly felt it may be the pick-up coil causing these problems. If I could get some backup on this one I would greatly appreciate it, it this could also be a culprit in this.

Very well could be the pickup coil...that's what Blownfuel was refering to. I'm at work so I don't have my FSM...but your mechanic should be able to ohm the pickup coil....just make sure to tell him to wiggle the wires while he is checking it, that is an important part of the test.And, I'm thinking if the pickup coil is bad it could explain why the fuel presssure dropped....unit fails, no signal to the ECM to fire the injectors.

Yes, that's what I was refering to, should be two wires leading to/from it (orange and white, if I remember right). they are the two wires that plug into one side of the module and the disappear underneath it. Mine failed just outside the entrance to the Like Like tunnel in Ohau, Hi! :willy: That probably doesn't mean much to most of you, just picture driving up the side of a volcano on a two lane road with no shoulders! At least it failed JUST before I entered the tunnel (instead of waiting till I entered it, cause I would have had to roll backwards back out against traffic, cause it's a steep uphill, and there's NOWHERE else to go! :eek: ) and there is a maintenance vehicle pull off right at the edge of the tunnel! Feild stripped and repaired it right there on the side of the road, was back in action in about an hour.

ok sounds like that may be the next thing I look at, I believe the wires are green and white. That's crazy about the tunnel story haha. What should the wires ohm at while wiggling?? what makes a pickup coil go bad?

Green and white sound kinda familiar too, the insulation breaks down on them and allows them to short, thats why you have to wiggle them. I'm not an electrical genius (so if I get this wrong, somebody jump in and correct me), but I don't think you need a specific reading, your just checking for continuity, and for a possible short. All this is is a magnetic switch, the voltages induced are pretty tiny.

ok, i'll keep that in mind thanks bud

well....kinda bad news...the problem seems to have regressed, while I was gone for the weekend my mechanic said the car died on him a few times in a row, and the car would NOT start up right away and had to wait for a few minutes before he could start it...could the module have failed again??? this is just getting stupid now

had a discussion with mechanic, he believes strongly it could be a bad ground causing these problems, can anyone support that? The main thing he noticed is that the fuel pump doesn't always power on with the key turned to the ON position, as it is supposed to, and those are the times when the car will not start right up and maybe take a few minutes to be able to start. At the other times when the pump DOES come on, it starts up right away as it should, good and strong. Anyone know where I should go from here?

One step at a time. Re; pickup coil, it should read a steady 500-1500 ohms while wiggling the wires, he should also connect the ohm meter to each terminal of the pickup coil and ground it to the distributor base..it should have an infinite (OL) reading on the digital ohm meter.

Since you're back in the dist. it wouldn't hurt to run that ign. module back down to NAPPA, highly unlikely it failed..but you wouldn't be the first to get a bad one.

Two other things I'd have him check 1. behind the battery is a power terminal..several wires attached, make sure they're clean and tight! one of these is a fusible link which provides power to the FP relay and also the oil pressure switch.2, I'd have him check to make sure the connections to the ECM are clean and tight.

The fuel pump relay will not come back on in less than 10 seconds.So, if you turn the key to ON, you should hear it energize, but if you turn the key off and right back on you will not.Hope this helps.

The pump should prime when you turn the key on, but after turning the key off, you have to wait for about 5 seconds before it will prime again. Listen for the click. Other than that, the pump primes entirely based on a signal from the computer, and does not require anything else. If this is intermittent, your ecm, or ecm ground signal to the relay, or the relay, or the pump harness, or the pump is failing intermittently.

Yes, this could all be over a loose ground/open circuit. On my 86, I can turn the key on and off as many times as I want and hear the fuel pump prime. The power supply wire/ground wire on the fuel pump assembly, in the tank, could be loose causing the pump to cycle on and off. I would take the igniton module to Napa and have them check it again too make sure. Attach a fuel pressure guage and drive. Test the fuel pump connection harness while wiggling, light should be bright the whole time. You will have to use the hot wire terminal G to get power to the pump for more than 2 sec. When the key is turned on it will only send power to the pump for 2 sec then it cuts off.

My 85 had ground issues too so I ran a 2 gauge ground from my battery to the chassis, then daisy chained another 2 gage up to the driver side head.

It could be a bad pickup coil when it stalls does your mechanic check to see if it has spark at one of the sparkplug wires?Also does your mechanic have a noid light if so when the car is in a no start condition plug the noid light into the injector harness and crank the car if the noid light flashes that will let you know that the computer is signaling the injectors that still doesnot say your computer is ok because they can some time work some fuctions and not others,your computer could be bad and not know its bad and not show a code indicating its bad.I have seen it happen on more than one occasion:thumbs:

Alright, again thanks EVERYONE for the detailed input, this must be getting frustrating for you guys i bet. I want this to be over! but i'm being extremely patient. I'll try to report back whenever I can get him to perform these tests, and I ordered a new pickup coil for like 10 bucks on ebay should be here in a few days, but will perform everything else suggested this week or weekend sometime.

Just a little info for everyone that gave advice. In the beginning of all this, when we thought it was the fuel pump, mechanic noticed that fuel pump wasn't turning on with the ignition in the ON position, so he installed a manual switch to the fuel pump, that gets the fuel pump to turn on so that the car will run. So I don't know if that helps at all.

Did you find the problem yet?:thumbs:

no, pretty much back to square one. waiting on the pickup coil, and in the meantime still going over things we've tried before. Seems like too many angles to go from, do you know of a FSM that is relatively cheap anywhere?

Can't help you with that,I use my snapon scanner when troubleshooting it has a troubleshooter program that is a big help,keep us updated. :thumbs:


LATERRR

Look on ebay, just make sure you get the ones for your year! And with the trouble shooting guides they provide...your problem most likely would have been resolved by now, and for alot less $$....sorry.

So how is it coming find the problem yet?:willy: