Not starting

[Channeled 91]

OK... I went out to the shop, Put a test lead with a light between the power wire and ground wire on an injector.No light. Turned the ignition. No light. Pulled the wire end off of the ground connection and grounded it to the block. turned the key on and the light lit. I am starting to think the ECM may be dead.

 

[PlayingWithTBI]

It could be but before you go there trace the wires back to the ECM and check those ground connections. look up your year and go to the truck wiring manual.

https://www.gmt400.com/threads/88-95-service-manuals.43575/

 

[Channeled 91]

It could be but before you go there trace the wires back to the ECM and check those ground connections. look up your year and go to the truck wiring manual.

https://www.gmt400.com/threads/88-95-service-manuals.43575/

I have done that.I checked the grounds for the ECM. The grounds are good straight to the engine. I replaced the end of one of the grounds. I did not like the fitting that was there.

 

[PlayingWithTBI]

What about the wires and any connectors going to the ECM, the pins in the connectors, etc?

 

[Channeled 91]

What about the wires and any connectors going to the ECM, the pins in the connectors, etc?

I have unwrapped all the wiring behind the dash and under the hood. everything is connected good.

 

[PlayingWithTBI]

How about sounding out the wire from the injector to the ECM?

 

[Schurkey]

Put a test lead with a light between the power wire and ground wire on an injector.No light.

Of course. It's not going to be powered until the ignition is on.

Turned the ignition. No light.

Of course. It's not grounded. The ECM isn't going to ground the wire until it gets a cranking signal from the pickup coil/ignition module. When the ECM does ground that wire, it's going to be for a fraction of a second--enough to pulse the injector. If the engine continues to crank, the ECM should continue to pulse the injector by grounding/un-grounding that wire.

Pulled the wire end off of the ground connection and grounded it to the block. turned the key on and the light lit. I am starting to think the ECM may be dead.

Wire end? WHICH WIRE? Ground connection? WHICH GROUND CONNECTION? The wire on the ground strap of the test light? And you grounded the test light to the block? With the ignition on? Of course the light lit. We've been telling you that the injectors are powered whenever the key is on. All the magic is on the GROUND SIDE of the injector circuit, and that means the injectors ground through the ECM, in pulses.

 

[Channeled 91]

tomorrow I will check the crank shaft position sensor.

 

[Channeled 91]

How about sounding out the wire from the injector to the ECM?

I lost you on that question.

 

[Channeled 91]

Of course. It's not going to be powered until the ignition is on.

Yes I know this. I turned the ignition on to test it.


Of course. It's not grounded. The ECM isn't going to ground the wire until it gets a cranking signal from the pickup coil/ignition module. When the ECM does ground that wire, it's going to be for a fraction of a second--enough to pulse the injector. If the engine continues to crank, the ECM should continue to pulse the injector by grounding/un-grounding that wire.

Yes I know this also. I was expecting the light to flash on and off when I turned the truck over.

Wire end? WHICH WIRE? Ground connection? WHICH GROUND CONNECTION? The wire on the ground strap of the test light? And you grounded the test light to the block? With the ignition on? Of course the light lit. We've been telling you that the injectors are powered whenever the key is on. All the magic is on the GROUND SIDE of the injector circuit, and that means the injectors ground through the ECM, in pulses.

The injector ground (ECM wire). The engine block. I understand the magic is in the ground side of the injector circuit. I was expecting the test light to flash on and off when I turned the engine over.