Testing Relays

[79F1504X400]

Trying to get fuel pumps to prime. But I was wondering if there's a way to check relays with an ohm meter. I'd like to check the pump relay and the ECM to make sure they are good. Every truck I've found in wrecking yards has already been picked clean of relays, so swapping out with a cheap one is a no go.

 

[Psychopete]

Trying to get fuel pumps to prime. But I was wondering if there's a way to check relays with an ohm meter. I'd like to check the pump relay and the ECM to make sure they are good. Every truck I've found in wrecking yards has already been picked clean of relays, so swapping out with a cheap one is a no go.

I can really only thing of 2 ways, but both are going to require that you figure out the wiring to test. First would be to apply 12 volts to the switching side of the relay and check for connunity on the other side that the actual fuel pump runs through.

Second would be to ground the fuel pump test on the diagnostic circuit and start checking where the voltage isn't to the relay.

FWIW, the computer controls the fuel pumps, it applys ground to the switching side of the relay from pin 22 on the computer main harness. The other positive is routed through the PCM relay. So it could be either the PCM relay or fuel pump relay. It could also be a bad fuse link.

The second method above would greatly narrow down what the problem is. Pulling diagnostics codes and getting nothing would also be some sort of verification that the computer is not getting power, or check for power on the large yellow wire running to it on pin #1.

Pete