I have an 86 v6 4spd that the fuel pump will not run. Before I drop the tank I just wanted to verify everything.

What I've done so far:

I jumped Pin G on the Diag Connector to the Battery. Nothing happened. It had a load on the circuit as i had sparks and the wire heated up when connected.

I switched the relay. Now what I didn't understand is I could never get anything to happen on the relay wires. All but one wire shows nothing, one wire showed 1 volt.


The car has been sitting since 05, could potentially be a bad pump just want to verify, thank you for any help and suggestions.

Don't drop that tank until you find 12v. at the relay. I think it is an orange wire....but have to check.

edit: There is an orange-black wire from the fuel pump fuse to the relay socket. Start with the fuse.

[This message has been edited by Gall757 (edited 04-24-2017).]

Yeah thought it was strange there was no trigger power for the relay. Anyone have a diagram?

Does,the ecu supply a signal and if so what should I see.

The computer is not part of this circuit. You get a lot of extra wires with this diagram!

IMO it would be a whole lot easier to test the fuel pump by applying 12v to the fuel pump terminal on the ALDL connector... which I'm pretty sure bypasses the relay (thus eliminating another variable).

quote Originally posted by Patrick: IMO it would be a whole lot easier to test the fuel pump by applying 12v to the fuel pump terminal on the ALDL connector... which I'm pretty sure bypasses the relay (thus eliminating another variable).

If you read the post I did do that

quote Originally posted by Phirewire: If you read the post I did do that

Well, what are you messing around for then... your pump is dead.

The fuel pump may be dead, but you still will need +12v at the relay.

Make sure you are looking at the ALDL correctly. It gets upside-down a lot, and then you would be connecting to a ground.

[This message has been edited by Gall757 (edited 04-25-2017).]

quote Originally posted by Gall757: The fuel pump may be dead, but you still will need +12v at the relay. Make sure you are looking at the ALDL correctly. It gets upside-down a lot, and then you would be connecting to a ground.

So I do have 12v on the Relay the other 3 wires test as "Ground". I didn't test the actual trigger on the relay and the functionality of the relay but what I am seeing is when bypassing the relay at the ALDL it shorts out, as well as at the relay itself. So Internal short on the fuel pump? I started the process of dropping the tank YAY! 2 Tanks in one month.

quote Originally posted by Phirewire: If you read the post I did do that

Most direct way to test. Disconnect the yellow fuel pump connector at the firewall. Using clip leads apply 12V directly to the black lead - (minus) and gray lead + (positive) Colors may vary by model year though. Check for fuel pressure. If you get nothing the pump is toast. If it is the original pump its likely bad.

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