Was on the highway the other night, and the car suddenly shut off.. Coasted to the side and got her towed home. Car cranks, just wouldn't start. Found the fuel pump fuse to be blown.. replaced it and the car fired up and shut off immediately. The fuse blew again, and now blows anytime the key is turned to the on position. Looking for a possible short in the wiring or possibly the fuel pump. Harness was built by Pocket, but he doesn't seem to be on the boards much these days, so does anyone know how the relays are suppose to be wired? I tested the relay terminals with the ohm meter and three of the four prongs are grounding out.

 

After searching threw Pockets threads it looks like the fuse thats blowing is connected to the PCM constant 12v as well as the fuel pump. Could something on that side be blowing the fuse?

 

I dont know how Pocket has the relay wiring setup on his harness but there are ways to isolate what the cause is.We need to narrow down at what point the fuse is being I would be looking for bad grounds at the fuelpump/tank,pinched/nicked wires leading up to the fuse/relay.I would also isolate the pump from the relay output..turn the key on and see if the relay/fuse function without an actual draw.If the fuse does not blow and the relay clicks/primes..you know your looking more indepth from there back to the tank itself(worst case) the pump is failing for some reason and needs to be addressed.

From past experience on my car over time my pump(walbro 255) got weak and you could hear it whine.I found at the tank the original ground wires to be brittle corroded garbage and replaced it.that helped alot.I then got a dedicated highamp fuel pump relay hooked directly from the battery and ive since never had issues of poping fuses or going through fuel pumps.

 

I doubt Pocket would put fuel pump on same circuit as ECM 12V constant. The ECM has low current draw, and the fuel pump has high current draw. You should not use​​ the same circuit protection for both.

First figure out what is really on the circuit with the fuse that is blowing. The nice thing about a short is that it can be tested with a simple continuity check and isolated to the wire, connector, or device that has the problem. You might have to unplug things to do the check but as far as electrical problems go, it doesn't get much easier than that.

 

The factory has the ECM and fuel pump on the same fuse, not sure why but they do.

 

Huh, go figure. Lovely 80's GM engineering. There are other reasons why you would not want fuel pump motor on the ECM power input but what's done is done.

 

The pump could be going bad and pulling too many amps get a amp clamp or put a multi meter in line and see what amps it pulls before the fuse pops

 

Thanks for the reply guys!

So I did a continuity test with the ohm meter on the fuel pump relay. First I unplugged the fuel pump at the bulkhead behind the rear seats. Then probed the fuel pump power wire at the relay and it was grounding out. I unplugged the c207 connector under the dash and found that it wasn't grounding out anymore. So I probed the interior side of the c207 connector and it was grounding out.. I ran a new wire from the interior of the c207 to the fuel pump bulk head behind the rear seats, and it fired right up.

 

Awesome buddy,celebratory burnout for good measure?

 

Great trouble shooting right there! Good job!