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Q: No power to the fuel pump

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I was driving home one friday, and stopped at a light. The light changed and I started to accelerate and bam my truck stopped accelerating and I pulled over to the shoulder. After getting towed home I looked for the problem. I discovered my fuel pump was not working. So I ordered a new fuel pump not testing the old one. I took off my bed, and replaced the pump. But to no avail, I wasn't getting power to my pump. So I decided to test the old pump using a power source and the damn thing ran... I don't know where to go from here, I tested my fuses and relays and they were all good. What's my next step?

My car has 220000 miles.
My car has an automatic transmission.

Hi. I would go back over a few things. Specifically, the fuel pump relay and fuses. Check the voltage drop across the fuel pump relay while trying to start it. An older relay will pass a resistance test (the contacts do indeed touch) but won’t pass enough current because the contacts are burned.

Also check the fuses for the ECM as well. Check the oil pump pressure switch - this is a low oil pressure fail-safe to protect the engine. Last but not least, make sure the ground for the fuel pump itself is good and clean. When you removed the bed, you removed several ground wires for taillights, and the fuel pump. Make sure it’s back on with a good clean ground. If these checks are not successful, I would recommend having an expert, like one from YourMechanic, inspect the loss of power and address this issue properly.

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