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Super Mechanic
Super Mechanic, Master technician
Category: Chevy
Satisfied Customers: 17220
Experience:  29 yrs. exp., ASE master, cert. in G.M. electrical, a/c, susspension, brakes, electronic steering
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96 Chevy Astro: no power going to my fuel pump..pump

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I have a 96 Chevy Astro. I have no power going to my fuel pump. I have changed the pump relay since it was a cheap try, to no avail. I have probed all 4 of the wires of the harness, and only have low power for the sending unit. I have checked fuses too, but all are ok and none say anything about the fuel circuit. I know it could be tied in with another circuit, but I thought with as important as the fuel circuit is, it should be marked in one of the two fuse boxes I checked. Any thoughts?    Ken

Hello and welcome to Just, Super mechanic here. About your vehicle.

You will want to check the ECM 'B' fuse in the under hood fuse box for power on both sides.

There is also a fuel pump prime connector that you can run power too just to see if the wiring is okay from the relay to the pump. If I remember right, there were some that had connector packs under the driver seat, that would sometimes get a bad connection. Here is a diagram that may help find the power loss.


Super Mechanic and 3 other Chevy Specialists are ready to help you
Customer: replied 8 years ago.
OK, lots more questions. First, there is power to both sides of the ECM "B" fuse, with the fuse in. I looked under the driver seat and did not find a red wire for a fuel pump prime. But under the fuse box under the hood, there is a red wire with a spade connector that I put a positive jumper to, and nothing. I tried both with the key on and off. I used my meter and probed the wire to the plug of the fuel pump relay and was able to get a resistance reading on one post. So it must be the correct wire. I did not find any connector pack under the seat either. Everything looked to be for the power seat. Looking at the diagram you sent, it looks to me the next place to look would be maybe a faulty oil pressure switch. My last question, it seems like we are heading in a direction of solving this. With the diagram and such, if we resolve this, I would like to pay you more for your time. Do I hit accept and pay you personally, or is there a way to change the amount I am willing to pay. Thank you for your time!! Ken
You can always add a "bonus" after the initial accept, thanks.

Sorry when I said under the seat, I meant on the under carriage, below the seat, sorry.

It sounds like you found the fuel pump prime connector. So you can run power to it and see if it is getting to the rear connector at the tank for the pump. Then, the power will run through the pump to the ground, (another thing that could be a problem) and you want to make sure that the ground wire, (from the tank) doesn't have power. If it does, you can ground it and the pump should come on.
Customer: replied 8 years ago.
Ok, when I jump the fuel pump primer, it gives me power going back there. I was not able to get the pump to turn on though. Using your wiring diagram, I probed the oil sending unit. I had power to the orange wire all the time. And had power on the grey with the jumper in place. None with out the jumper, and none with the key on or in the cranking position. The fuel pump did not prime any of this time, and I was not able to get a good ground. Sounds like the oil pressure sending unit huh?
No, the oil pressure switch is only for after the engine starts. It sounds like the fuel pump is not working. Try hitting the gas tank with a rubber hammer, (or your foot) while the primer is powered. You might hear it start to humm. That will sometimes jarr them to start working again, but you would still need to replace it.
Did it start after you hit the gas tank?
Customer: replied 8 years ago.
No. I pulled the fuel tank and was going to pull the pump out, and I noticed the one connection in the plug had melted. There was no contact at that plug. I ordered a new fuel sending unit, and we are now up and running. Sorry it took so long to get back to you, I just wanted to see if this was the whole problem. Thanks again for your help! I would definitly like your help with any future problems. Thanks again!
Good job!...They can be tricky sometimes. Thank you and do come again, anytime. Glad you found it and thanks again.