I have a ecu from a firebird 1992 in my hot rod, and it runs a 350 TPI engine. It used to run fine, no problem. But after lifting the body off the frame. It looks like I might have ripped a wire. I have searched a lot for an ECU Pin out diagram, but cant find any.
I hope its the ripped wire that is the issue of no start.
The ripped wire is an orange one on the yellow connector. Position 5 from left on top ( a bit hard to see though)

 

 

That was not my issue, the rioppd wire is for the diagnosis.
So I have been chasing a no fuel problem for the last 2-3 weeks.
The fuel pump primes, and have good pressure, about 47psi at the rails. It primes for about 2 sec, then stops. When cranking, no fuelpump. When I stop cranking, the fuelpump starts again for 2-3 sec.
I do not see an injector pulse using noidlights. I dont see a distribution pulse to the ECM, the wires are good though and continous.
I have 12v at the injectors prior to cranking. I have no vats in this car. I have checked grounds, and they are all good.
I have spark, its a strong spark also.
I have checked tps also, that is within range 0,5v to 3,9(WOT), smooth increase.
I am a bit stumped now on what to check next.
The car ran 6 months ago, I just had to take it apart to go the the dmv with the frame only. Most of the wires are attached to the frame, and I did not have the need to remove that many, just the ones to the dashboard.
Will this problem point to a faulty distributor/ICM? Or are there any other things I need to look into?

 

To control the fp relay the ecm does 2 sec prime when ecm
is powered on . Then it controls the fp relay when cranking the ecm
needs to see drp. Your backup ops isn’t working. Possibly you have a bad icm
or wiring from icm to ecm.

 

To diagnose the icm it can be tested at air parts stores but can unplug the pu coil first and check for acv while cranking .

 

Doesn't the ECM need to see the oil pressure sensor as well to keep the FP relay going after crank? Maybe something going on there?

 

The ops is not needed it’s backup if relay fails a parallel power circuit.

 

 

Might want to run through all the connections if you haven't already..

https://www.gearhead-efi.com/Fuel-In...2&d=1322074874

https://www.gearhead-efi.com/Fuel-In...1&d=1322074869

https://www.gearhead-efi.com/Fuel-In...0&d=1322074863

 

Everyone on this site that is not 100% familiar with all the in & out workings of the engine management systems our 3rd gens use should watch this video.

This is not a how-to, walk-through video for repairing a 1987 Firebird Formula with a LB9 5.0L TPI engine with a 5 speed manual transmission, CC1 factory T-tops and a rear cargo compartment roll-up security sun shade. If you want detailed, specific information about your exact car then refer to the factory GM service manual for your exact car.

This is a very good video explaining the how & why things work on our cars and is targeted to around the 1988/1989 timeframe and before, though it also has plenty of information that still applies to the 1990 to 1992 cars and other GM cars & trucks until 1995.

He mis-speaks a few times in the video but he corrects himself right after.

ALCL (Assembly Line Communication Link) you might know it as the ALDL (Assembly Line Diagnostic Link) or GM (OBD I) connector.

When he says Chevrolet he mean Chevrolet engine not Chevrolet car. When he says non Chevrolet he means non Chevrolet engine not non Chevrolet car.

I have the video queued up to start at the Fuel Pump Electrical Circuit portion of the video. Most people misunderstand how this system actually works. He explains it perfectly.

The oil pressure switch and wiring circuit could be completely removed and the engine would start up immediately and run just fine. The oil pressure switch and wiring circuit is a redundant power backup system for the fuel pump. It does not shut off the fuel pump if oil pressure gets too low to protect your engine from damage. It is not a rollover protection system to cut off the fuel pump if you wreck your car.

GM Port Fuel Injection Training VHS by AVI - 80s / 90s How-To Tape

 

Thanks for all the feedback, I have some things to check now.

The car is hot rod, and I have just wires from the ecm to the engine and some other bits, but not a complete body harness. The oil pressure is not connected in the ciruit as far as I can see. But the car ran fine some months ago, I havent changed that bit.

But I cant see a signal from the distributor to the ecm, so I hope thats where I need to look further.

 

Look for a open in the icm purple/white wire from icm to ecm.

 

Found this trouble shooting steps in a youtube video, and they also state the troubles might be in the purple/white . 430 - referance. So going for this today to see.

 

After perfomring the above troubleshooting, the injectors fired fine. Meaning the wires and ecm are fine. Looks like it was the icm that was the culprit this time around.

Thanks for all the feedback and diagrams.