Longshot379

1988 5.7 IROC. No cold start injector. No VATS. Engine was running very strong. Started shutting off like you turned the key off. found one coil connector loose, fixed that problem. On the test drive to test coil problem the engine started sputtering like it was running out of fuel. Fuel pressure is 45psi. Checked spark with a HEI spark tester{have spark}. Checked pick up coil. Ohmed good. Noid light will not flash.
The problem I found is battery voltage on both sides of injector wire. All injectors ohm at around 15.6. Disconnected all injectors and still have 12.7 volts on both wires at injector connector. What would cause this? Bad ECM?

Vader

The ECM must receive the ignition reference pulses from the distributor in order for it to count the pulses and develop the injector pulses. Considering that the coil wiring had a problem, I would investigate the coil primary and EST circuit wiring.

Longshot379

Po installed a aftermarket coil with a harness to plug into factory connecters. One had come unplugged.

Longshot379

I have a reference signal out the distributor and icm to the ecm. What I have a problem with is battery voltage on both wires at the injectors,even with all of the injectors unplugged.

Tootie Pang

iTrader: (2)

Was it shutting off at idle or at any throttle?

Longshot379

Any thottle.

Tootie Pang

iTrader: (2)

Does it just die or does it die and backfire?

Longshot379

Sputtered like it ran out of gas. It hasn't started since.

Vader

I am uncertain how to interpret that statement. Does it mean that there is NO battery voltage at the injectors? Does it mean that there is battery voltage on the ECM side of the injectors as well as the B+ side of the harness?

Tootie Pang

iTrader: (2)

Due to your first statement: "Started shutting off like you turned the key off." it should be an ignition problem. That shutoff is too fast for a fuel problem which would take noticeably longer than a key-off shut down.

Longshot379

I have battery voltage at the injectors on both sides of the injector connecter only with any injector connecter hooked up. With no connecter hooked up, I have power on the power side and no power on the ecm wire( at the injector connecter)

Longshot379

I have since received a FSM and am proceeding thru the diagnostics charts.

backtothe80s

Keep us posted!

Vader

That is normal. the INJ1/INJ2 fuses supply B+ to one side of the injectors. With no ground connection on the "switched" side of the injector harness the 12V+ supply will also produce voltage on the other side of the injector harness. The injector solenoids are only 12-15Ω each, and following Ohm's Law, without current flow the voltage at the other side of the solenoid coil (switched side) will also be 12V+.

If you ground the switched side does the injector fire? It should. That is exactly what the ECM does to operate the injectors.

Refer to the schematics for clarification.

Longshot379

Followed fsm diagnostic chart for crank, no start ended up checking injector driver wire circuits. I had continuity on both driver wires. The only thing left was the ecm. I had ordered a ecm and it came in Saturday. Installed it Sunday after putting the wiring harness back together and car fired right up.

NCC-2569

iTrader: (1)

What a nice thread. Problem, advice, solution.

Thank you very much for the info about those 12Vs on the injector wires, Vader.
That'll help me some day along the road, I'm sure.