Whats up? I've had my GTA for about 3 weeks already since its been in the shop from getting a re-rebuild. Anyway, I developed a wierd intermittent stall issue where it just dies and won't start until about 5-10+ minutes of sitting. This has happened to me 3 times already: The first time I was with a buddy of mine and made a sharp right turn while giving it mid throttle (WS6 suspension handles good ) when it flat out died in the middle of the street. I cranked and cranked it but it wouldn't fire up. We both pushed it around the corner into a parking lot while we called to get some help from a friend to push it back to my friend's house which we did. It sat for about 10-20 min. cranked it and it fired right up. Later that night, we went for a ride again and I decided to punch it pulling hard as hell until it flatlined once again. The car was still moving to where I parked it in a not-so nearby neighborbhood. My friend forgot his cell phone this time so we had to walk back to his house which took about 15 min. We got ahold of his neighbor once again to help us push it back with his truck but I wanted to see if it would start first. A few cranks and it started up and drove it back. Since then, I cleaned and adjusted the IAC Valve (not the passages). I thought this helped out since it was running smoothly until yesterday when I was with another buddy of mine who dared me to punch it. I did and again it pulled nicely. All was well until we we're leaving the mall backing out of the parking spot when it just stalled again. I cranked and cranked this time but nothing. I waited 5 min. before I cranked it again and nothing. Finally after about 10-15 min. I cranked it and it started right up. Its been running good since then. I guess this just happens when I give it semi to WOT. I've looked at other threads but none relate to my issue. I guess I should also point these important details: my EGR valve is not hooked up at all and just noticed last week that I have no EGR valve solenoid, A.I.R. tubes are possibly not hooked up properly either since one check valve is missing (been like that since I bought it), TPS appears to be 'skipping' when adjusted properly with a VM, and lastly, hot or cold when I crank the car it will fire up but won't stay on unless I give it some gas for about 15 sec. then it will idle on its own. Occasionaly it will idle really low in "D" and die out but it happens rarely. Anyone got a clue of the cause of my wierd problem???? Thanks alot guys for any input. Later, Phoenix

Thought I'd mention also that my SES light comes on after about 10 min, of driving, I tried pulling trouble codes but only get code 12. Quick question, would bypassing the OPS cause something like this to occur? Thanks again in advance.

Phoenix

Today I took a cousin of mine for a ride who also dared me to punch it which I did. He was impressed by how quickly it picked up. I headed out a while later after it had been sitting for 2-3 hours fearing the car would stall again after a putting it through a few WOT sessions but low and behold, it didn't. I don't know why but for some reasom I'm thinking its the TPS since it appears to be the original unit, I think I will replace that first and see what happens. I'll keep you guys posted.

Later,
Phoenix

Replace the ops if it is bad, don't leave it bypassed, check for vacuum leaks, also check the relay connectors on the firewall for exposed wires and insulate if necessary.
I had issues with all of these on both my cars. They all caused my car to act like yours is.

The shop I had my car at recently for the rebuild is responsible for bypassing the OPS (didn't even let me know about it). I was facing a continuous running f/p problem which long story short caused a bent piston rod. Apparently the dumb***** at the shop thought bypassing it would do the trick which it did I'll admit but I'd rather have my car working the way it is supposed to. I already have a new ac delco OPS waiting to be installed since the shop didn't want to install it; the shop said the OPS' function to cut off fuel when no oil pressure is present doesn't occur in my year of vehicle . Today I'm going to readjust the TPS to .54+/- volts since its currently at .50 volts, I'm going to clean the passages as well and adjust the idle properly since the idiots at the shop probably didn't do it right either. I'm waiting for my new TPS to arrive so I can install it. Thanks very much for that input john 89 formula I will do that.

Later,
Phoenix

The oil pressure sensor is only for backup power to the fuel pump, in the event of a relay failure. It will supply power to the pump once oil pressure comes up. (which tends to make for long crank times if the relay doesn't work.) It is in no way shape form or manner a "Low pressure cutoff switch". If it was, you car would NEVER start until oil pressure came up. This is true for all thirdgen cars, regardless of year.

^^^^ What he said.^^^^^^

on your '89 the ops also is the sending unit for the oil pressure gage, if you've noticed it's not working, thats why.

john

Thanks for clearing that up. The reason the shop didn't bother to change out my current faulty OPS is because they thought that it just marks oil pressure. Also the reason they bypassed it.



Right! It actually doesn't appear to be working since the gauge needle is pegged all the way to the right aside from the continuous running fuel pump problem it also caused . This might mean the OPS might have an internal short huh?

I received my new TPS a couple of days ago and will be installing it later today. So far the car has been running like a champ but it should run a bit better now that the voltage won't be skipping. Hopefully this will end my wierd stall problem which could happen at any time when I give it WOT. I'll let you know. Thanks for the info guys. I appreciate it.

L8r,
Phoenix

If the ops is properly connected and the fuel pump will not shut off, it is defective. replace it, a good one will cost you about $20.

In the future steer clear of that shop they never should have done that, it was unprofessional.

I already have a new ac delco unit from oehq.com waiting to be installed, just haven't had time. I agree about the shop bieng unprofessional, they shouldn't of stuck their hands in a car they knew nothing or very little about.

Thanks again

Phoenix

This subject comes up and someone always says the ops backup power thing.
Then in contradiction say if the pump won't turn off the ops is shorted?
It's my understanding that the ecm powers the pump for a few seconds to pressurize the rail for quick startup then leaves the relay dead and under control of the ops for obvious key left on reasons.
If I am wrong and the ecm continues to supply the pump based on ignition signal, what then turns the pump off in the event of a roll over?
I get the feeling someone unplugged the ops wire and since the rails still had pressure and the engine didn't die, started claiming the ops only provides "backup" power to the fuel pump if the relay dies, hence long crank times....HUH? doesn't this prove the ecm only primes?http://www.thirdgen.org/techboard/im...lies/hmmmm.gif
Shut off engine no oil pressure no pump, turn on key fuel pump primes then turns off, turn key to start, engine turns, oil pressure builds as engine starts on rail pressure, oil is up to pressure, fuel pump runs, turn ignition off oil pressure dies and fuel pump does as well. So what am I missing?
I don't care if this is an old thread, age means nothing to me.

So it may be possible the ECM is defective and causing the fuel pump to continue running? The switch is still bypassed at the moment which also temporarily fixed my continuous running fuel pump problem but will definately get it hooked up the proper way soon (with the new switch).

You need to do your homework. Breifly, the ECM runs the pump, via the relay, for a few seconds at initial key on to prime the pump. It then waits to see crank referrence pulses, indicating that the engine is cranking, before it re-energizes the relay. The OP switch is intended to act as a safety fuel cutoff in the event that oil pressure drops off but GM didn't program this function into the PROM of the ECM until 89. Thus, on 85-88 cars, the OP switch acts as a back up for the relay. Stupid I know.

Its very unlikely that your ECM is causing the fuel pump to run on. The ECM controls the fuel pump relay. If it was keeping the relay energized at all times, the pump would have run on without the OP switch. Check your wiring carefully for any shorts. The pump only runs on with the OP connected so start there. Be sure that the new OP switch/sender is right for the application and that it's not causing the problem.

As far as your stalling/no restart after hard acceleration. It really sounds like fuel supply. Use a fuel pressure gauge taped to the windsheild to monitor fuel pressure while trying to recreate the failure. If fuel pressure drops off as the engine stalls and wont come back up when cranking, suspect the fuel supply system(pump, filter, lines). Also, check spark using an inline spark tester taped to the windsheild so you can see it while driving. Watch for spark to drop off when the engine stalls and no spark while cranking after the stall. If no spark, suspect ignition module or pick up coil in distributor. Note: Pick up coil failure and certain ignition module failures will also cause a loss of crank referrence pulse to the ECM. Loss of this pulse will cause the ECM not to energize the fuel pump relay or fire injectors. In this way it can mimic a fuel system failure. The difference is the no spark.

Thanks for the info ASE doc! The stalling issue I had with my car when I would mash the gas hasn't occured for about a year and a half now ever since I replaced the TPS.

I kinda ruled out the ECM as well since I replaced it with a "new" 16198259 (1227165 equivalant) unit. I'm leaning towards a bad OPS or a possible short in the wiring harness which I'm going to have to replace evantually since the dumba**** hacked the wiring up to bypass the switch. Other than that though the car has been running fine.

Phoenix

ASE Doc, I went back and did some homework and I understand what this circuit is about now. You are correct, I was over thinking the whole thing because I was so wrapped up in the safety aspect, that I just couldn't believe there is no provision for fuel pump shutoff (in the event of an accident or roll over other than loss of ignition signal.
I am seriously considering an inertia switch now as I am not comfortable with a low oil pressure shut down switch scheme (as stock it is a relay helper) regardless Aloha