95 GMC Jimmy

Sometimes the relay works and some times not. If I put in a new relay it starts. If I put the old one back in it starts. Meaning the fuel pump runs. I'm burning through relays. I must always have a backup ready. What might cause the relays to burn up?

 

You have a short circuit or high voltage, verify connections to the fuel pump first.

 

There is a wonderful "test port" available to you under the hood, near the battery distribution buss out-board of the brake booster. There should be a wire with a connector hanging loose.

IF the fuel pump relay is "DE-ENERGIZED" THEN connecting juice to this port will cause the fuel pump to run. If the relay is energized, but failed (contact burned open) then putting power to this port will NOT make the pump run.

It should draw 4-6 amps, AND you should get pressure to the fuel test fitting behind the air-valve. If the current draw is in this range, then your fuel pump is not drawing too much current.

IF, as you say, the fuel pump relay "fails" AND applying voltage to this port makes the fuel pump run THEN the relay may not have failed at all, but may be de-energized by the ECM or some safety circuit.