Ok. I just installed a '94 Camaro 3.4L engine with SFI and DIS into a previously carbureted car. So, I converted the harness to stand alone the best that I could figure out. I took care of the pass-key security feature etc. and I got it to start up. Here's the problem, it starts up - runs for about 2-3 seconds - sounds fine doesn't sound like it sputters or the ignition timing gets retarded or anything like that - then it just dies. I wish that I could narrow down a few possibilities on my own -- but I'm really not very familiar with troubleshooting all of the electronic systems. I know that for the most part, if the PCM (powertrain control module) was hooked up wrong, it just wouldn't start at all. I also know that 95% of the problems that could be caused if a sensor was bad, etc. would not cause the engine to just die. I don't know where to start -- please help!!!

 

does it stay running longer if u give it gas?
what does it idle at before it stalls?

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- David
88' GTA 5.7L TPI MODS---> air foil, K&N, Shift Kit, 180* therm, TB bypass, Gutted CAT, Flowmaster 80 Series

http://www.geocities.com/david_angel_16

 

It instantly dies if I give it any gas. Approximately 900 rpm.

 

Will it idle indefinitely?

If it dies after 2 seconds no matter what, it's the oil pressure switch that supplies power to the fuel pump. The FP relay only operates for a couple of seconds right after you turn the key to "On", and after that, only while the key is in "Start". Once the engine is running, power is supplied to it through an oil pressure sending unit, suchthat if the enginestops running, the fuel pump stops too (safety).

This is a very common problem when people do major work that involves the car's wiring. It's not an "electronic" problem, just an electrical one. You'll need to find the plug for that in whatever harness you have, and equip the engine with an appropriate sending unit.

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"So many Mustangs, so little time..."
ICON Motorsports

 

It dies after 2 seconds no matter what. Good guess. But, this was an engine swap, so for testing purposes, the fuel pump is hot wired -- so I know that it's running.

 

Do you guys know of any sensors that will cause the PCM to shut the engine down? (To my knowledge, most of the time, even if a sensor isn't sending feedback to the PCM, it will throw the PCM back to a default 'failsafe' like limp home mode rather than shut the engine down.)

 

So is the fuel pump really running? Have you checked for fuel pressure at the injectors immediately after it shuts down? Can you keep it running for a few more seconds by pouring more gasoline in it or spraying carb cleaner (NOT brake parts cleaner) or starting fluid in it?

You have a fuel problem by the sound of it. I'd investigate that thoroughly before moving on to more complex theories.

"The simplest explanation that fits all the facts is usually the right one."
— Occam, ancient Greek philosopher (uttered before FI, I think they were still using carbs at the time, but it still applies)

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"So many Mustangs, so little time..."
ICON Motorsports

 

It's hot wired. I manually connect a positive and negative lead to the fuel pump directly for the purpose of getting everything running and tested. I have the fuel pump inline -- so I'm able to hear and verify that it remains running past the point in which the engine dies. However, I will be testing that, just to be on the safe side. Do you have any other suggestions in the case that it is not the problem (which I'm 99.9% sure that it is not.)