No Fuel No Fire in 94 s10/4.3z TBI

[russellaporter3]

I would greatly appreciate some insight into this problem with this truck. I have a 1994 Chevy S-10 with a z code 4.3L TBI on an auto. This truck was runnning fine, I parked it and shut it off and 3 hours later it would not start.
It does turn, the starter is strong.
It is getting power (+12v on the plugs) to the injectors, as well the resistance on the injectors themselves are fine. There is fuel line pressure to the throttle body. There is voltage going to the coil, but no spark coming out.


#10 Fuse labled ECM/IGN is good, has +12v as checked from the hot side of the fuse socket to ground.

Replaced:
Coil
Fuel Filter
Ignition Control Module
Fuel Pump

Any Ideas?

[old_master]

1) Check for ground pulse at the dark green and dark blue wires at the injectors while cranking.

2) Does the fuel pump run for 2 to 3 seconds when the ignition switch is initially turned to the RUN position?

3) Does the fuel pump run continously while cranking?

4) What is the fuel pressure with the ignition switch in the RUN position, (engine off) when the pump is running?

5) Does the pink wire at the ignition coil show battery voltage when the ignition switch is in the RUN and START positions?

6) Does the white wire at the ignition coil pulse ground while cranking?

[jdash]

1. Dark Green Wire and Dark Blue(at injectors) both have power to them when key is tuned on. No pulse, solid power(injector will click when push grounded light tester in wire, as well as light to show power).
2.Yes, fuel pump runs for a few seconds when turn key on.
3.No fuel pump does not run while cranking(only when first turn key on).
4.Unsure what fuel pressure is, not sure how to check.
5.Yes pink wires show power with key on(at injectors).
6.Not an issue for me, truck will run whn pour fuel directly in top of throttle body.

*note: TBI injectors simply will not deliver any fuel from them. Fuel pump comes on, power at injectors. Just do not know enough about these tbi to know where to look next. Is there a fuel relay that could be the culpret?

Please help if you know.

Thanks
jdash

[old_master]

1. Check for ground pulse at the dark green and dark blue wires at the injectors while cranking.

You're not looking for power at the injectors, you're looking for ground. Use a non-powered test light, or a "noid light". Connect the ground lead to battery positive and the test probe to each of the injector wires while cranking. The test light should pulse, (blink).

With the ignition in the RUN position, (engine off) all 4 wires at the injectors should show battery voltage. The injectors are supplied battery voltage when the ignition is in the RUN and START positions. The PCM sends a ground pulse to open them. When the PCM sends the ground pulse, the dark green and dark blue wires should show a pulsed ground at the injectors.

If that checks out ok, here's the next step:
If the engine runs when you manually put fuel in the throttle body, your ignition system is fine and the problem is fuel delivery. Check fuel pressure at the throttle body. TBI requires 9psi to 13psi measured at the throttle body. Some auto parts stores rent the tester, but you need to make sure it will test TBI systems, (some don't).

[jdash]

Thanks for the advice on checking the blue and green wires on the tbi. It appears I hae no ground pulse. When connecting the test light to the battery positive and the blue &/or green wires, the light will come on with key in off position. As soon as you turn key in on position the light goes out. Of course when cranking the light remains off. When I turn key back off, light comes on. Again, thi is with alligator clamp end on battery positive and probeend on blue 7/or green wires(seperately).
Therefore, appears pcm may most likely be bad(correct) where is the pcm located on this 1994 s-10 4.3 tbi?

Thanks again for the great advice.
JD