OK here's what I've done and here's what's happening.
I replaced my 2.8 in my 85GT because of a horrendus rod knock, with a used 2.8 out of a wrecked 86SE. The donor car was running fine at the time of the accident but the car had set for I don't know how long. Before I installed the motor, I was able to turn it over freely with a socket on the crank shaft pulley so I know it wasn't locked up from lack of use. I drained all the vital fluids and replaced them. New plugs, wires, cap and rotor just because I happen to have a set of each laying around. (Hey you never know when they'll come in handy ). I rewired the C-500 so the NSS would work on the manual tranny I have. (The wiring harness was set up for an automatic).

When I turn the key, with the clutch depressed, I can hear the fuel pump come on briefly like it should for a few seconds, and the car starts right up but it only stays running for about 10 seconds before it dies. Then it will crank but not start again unless I let it set for a few minutes.

This tells me:
A: I have fuel
B:I have spark

If it starts, why won't it stay running? I'm pretty good when it comes to turning a wrench but lousy at diagnostics.

Help

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AIM-jaxpac257

[This message has been edited by paulcal (edited 03-22-2004).]

do you hear the fuel pump shut off after the engine dies?

Could be the oil pressure switch / relay is not working.

If the oil pressure does not trip the switch the pump will shut off and the engine will die.

While I'm cranking it and when it fires up, the oil pressure gauge is working. As soon as I engage the starter and the motor starts turning, the gauge is moving up to where it should be.

[This message has been edited by paulcal (edited 03-22-2004).]

quote Originally posted by paulcal: While I'm cranking it and when it fires up, the oil pressure gauge is working. As soon as I engage the starter and the motor starts turning, the gauge is moving up to where it should be.

Could be the relay

First of all, if the oil pressure switch is not working, the engine will run anyway. you say you hear the pump when you turn the egnition so that sounds good. check that fuel pump fuse, it is on the top row second from the left, the reason I say is I have had fuses to get coroaded and not make a good connection. The only other thing I can think of now is the ECM is not receiving a pulse signal when it starts. The distributor sends a signal to the ECM when it starts to let it know it is running. Could be a control module I just don't know. Hope you find the problem.
Don

20 bucks says it the fuel filter, thats what cured my start>dies problem

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Mark Panasevich
Black 85GT

AIM : Mjpana252
email : MJPana@Comcast.net

quote Originally posted by MarkJPana: 20 bucks says it the fuel filter, thats what cured my start>dies problem

Since I'm off work tomorrow and fuel filters are cheap, I'll take that bet. I hope you win.

Definantly wouldn't hurt. Fuel filters are recommended to be replaced every 6,000 or 10,000 miles i forget. Usually they can go for much longer but they are cheap =). Same with o2 sensors but that isn't your problem.

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-Kyle
Email: arte@sek-c.com
Aim: Littlechugger
1987 Notchback 4cyl. (Busted Tranny)
1992 Corsica 3.1L GT =P

Try replacing the ignition module with a known good one. It's probably not that, but the ignition module seems to factor in so MANY times in running problems. When the module went out on my son's car, it didn't die all at once. The car actually ran, although so badly, I had to take it to a mechanic because I couldn't figure it out. I had the module checked, too, and it checked out good. But as soon as the mechanic put the new module in, it started right up and ran fine. One other thing to check is the coil. If it's going bad, it could be that the field is collapsing after so many minutes. Good luck...

Unless both the oil pressure switch and the relay are not working it should crank and stay running. If you hear the pump run for a few seconds that tells me that the relay is working at least at first because the ecm sends a signal on the dark green/white wire going to the relay for about 3 seconds. It then uses a signal from the PU coil to continue to send a signal to the relay.

It seems to me that for what you describe to happen that either the ecm or pu coil is defective and your oil pressure switch is not working.

One easy way to tell if it WILL run is to hook up a 12V wire and connect it to the ALDL connector behind the cig lighter to terminal G. I believe it's the only one on the bottom row, but check to be sure. With it hooked up this way, the car should crank and run. If so, the oil press switch is definitely bad and the relay may be bad, depending on the readings at the relay with the car running. Give the above a try and let us know what happens. Good luck.

Phil

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87 FIERO GT 2.8 5spd

GM auto tech for 27 years. Specializing in electrical and computer problems. I enjoy helping all that need and appreciate help.

Again I say, The oil pressure switch does not have to be good for the engine to run. The oil pressure switch makes a direct connect to the fuel pump when it receives oil pressure, and the relay kicks out. if the pressure switch does not see pressure then the relay will continue to run the pump. Just try it. disconnect the oil pressure sender connector and all you will notice is that the oil pressure guage will peg but the engine will run fine as long as the relay is good.
Don

quote Originally posted by MarkJPana: 20 bucks says it the fuel filter, thats what cured my start>dies problem

This is going to get done regardless (sp) Thanks for pointing that out to me Mark. Easy to overlook the obvious.

quote Originally posted by litespd: Try replacing the ignition module with a known good one. It's probably not that, but the ignition module seems to factor in so MANY times in running problems. When the module went out on my son's car, it didn't die all at once. The car actually ran, although so badly, I had to take it to a mechanic because I couldn't figure it out. I had the module checked, too, and it checked out good. But as soon as the mechanic put the new module in, it started right up and ran fine. One other thing to check is the coil. If it's going bad, it could be that the field is collapsing after so many minutes. Good luck...

I know the one on my old motor is good so that gets swapped out tomorrow too. The only reason I didn't change it out to begin with is that I didn't have any di-electric grease around but I guess I'd better go get some.

quote Originally posted by GTDude: Unless both the oil pressure switch and the relay are not working it should crank and stay running. If you hear the pump run for a few seconds that tells me that the relay is working at least at first because the ecm sends a signal on the dark green/white wire going to the relay for about 3 seconds. It then uses a signal from the PU coil to continue to send a signal to the relay. It seems to me that for what you describe to happen that either the ecm or pu coil is defective and your oil pressure switch is not working. One easy way to tell if it WILL run is to hook up a 12V wire and connect it to the ALDL connector behind the cig lighter to terminal G. I believe it's the only one on the bottom row, but check to be sure. With it hooked up this way, the car should crank and run. If so, the oil press switch is definitely bad and the relay may be bad, depending on the readings at the relay with the car running. Give the above a try and let us know what happens. Good luck. Phil

Thanks for the info Phil. Can I just use the one from the cig lighter since it's right there?

quote Originally posted by ka4nkf: Again I say, The oil pressure switch does not have to be good for the engine to run. The oil pressure switch makes a direct connect to the fuel pump when it receives oil pressure, and the relay kicks out. if the pressure switch does not see pressure then the relay will continue to run the pump. Just try it. disconnect the oil pressure sender connector and all you will notice is that the oil pressure guage will peg but the engine will run fine as long as the relay is good. Don

Since this motor had A/C, this is an easy one to test with the pressure switch up where it is. Since this is the easiest, it goes 1st on my list of things to do in the morning.

Thanks everyone +'s all around and I hope to meet some of you at Ed Parks for those that are going. Hopefully I'll be driving mine by then.

[This message has been edited by paulcal (edited 03-22-2004).]

Went to the parts store and picked up a new fuel filter, some di-electric grease so I could swap out the Ingnition module and a 3/8" bolt to finish up my new grounding system. (pics later today of this)
I took the connection off the oil pressure sensor and that didn't help at all, sorry guys. Before I jacked the car up and got really dirty again I thought I would try someone else's suggestion and that did the trick. It still runs a little rough and won't idle but I think that's just a matter of the timimg being off since I Know I was off by at least 4* when I eyeballed it.

And the winner is................. Drum roll please...........................................

quote Originally posted by litespd: Try replacing the ignition module with a known good one.

Thanks again everyone for all your help on this.

P.S. Mark you owe me $20. you can paypal it to me at....ah the heck with it. I'm still going to replacde the fuel filter anyway. Forget the $20 I'm so happy to hear it run again I could forgive the national debt right now

[This message has been edited by paulcal (edited 03-23-2004).]