SOLVED: Fuel system electrical diag road block

[Curious Hound]

The pump needs to be ground by the ECU correct (its the LB/O wire that I am jumping and that goes to the ECU).

The pump RELAY is grounded by the ECU. The pump is grounded by the black wire at the pump connector.

 

[ecgreen]

The pump RELAY is grounded by the ECU. The pump is grounded by the black wire at the pump connector.

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Gottcha, that makes more sense. Eitherway, I can safely assume at this point that the ECU is to blame, yes?

 

[ecgreen]

Another ECU on the way

 

[ecgreen]

New ECU, same problem... must be the wire. Have to think it through again

 

[ecgreen]

So I jumped the obd wire for the fuel pump and the pump runs just fine. If the ECM is OK, then the problem has to be the going from the junction to the ecm, or the junction to the relay.

At what point do I tear into the harness?

 

[Curious Hound]

I think you should check the grounds for the ECU. The black/white wires at pins 40 & 60. Make sure all their connections are clean and tight.

 

[ecgreen]

OK, I'll check that, thank you.

Maybe you can clear me up on understand this system. I checked the continuity on the wires and connectors going from the ECM to the OBD and then to the fuel pump relay, they are all fine. They are actually tan with a green stripe (unlike the chart that say LB/O). When I ground the pin connected to that wire on the obd the pump runs. So what I am doing is providing the ground the ECM is failing to provide?

 

[ecgreen]

SOLVED: dumby of the year award goes to me. It was a ground issue! There is a connector off the battery wire that has a plug that ground the ECM. It was Freekin unplugged...LMFAO!!! Plugged it in a she fired up lmao.
Got the idea from this guy who did the same thing:

fuel pump not working.

hello I have a 1986 ford ranger super 4x4 2.9 with a/c. my problem is that my fuel pump is not turning on. I thought i ran out of gas one day. so i stopped and filled up then my truck would not start. so i checked the valve on the fuel rail and no gas. so i turned the key on and could not hear...

www.therangerstation.com

Thanks for the help guys!

 

[Curious Hound]

So what I am doing is providing the ground the ECM is failing to provide?

I don’t think so. I don’t have a diagram in front of me. But I suspect that when you do the obd jumper, you are bypassing the normal circuit that the ecu uses to energize the pump relay. It’s a function just for testing.

 

[Paulos]

Thanks for letting everybody know. I've seen that ground wire with a connector on mine many times, but never bothered to check where it went to.