This is mostly electrical, sorry if I put this in the wrong spot.


I installed a new external fuel pump and got rid of the mechanical one on my originally LG4 car. I'm now running a built 383 so the original pump wouldn't keep up. For a while, I was fine. Now every time I turn the car on and the fuel pump relay switches, the 20amp fuse for the radiator fan blows and the alternator no longer charges the car..... Super confusing. I already unwired the pump and just tripped the relay. This by itself blows the 20 amp fuse. Once the fuse is popped for the fan, the pump continues to push fuel (when it is wired up). None of this makes sense. When the FP relay is removed, the fuse no longer pops.


Any ideas guys?

 

Something's back-feeding through the fuel pump/relay straight to ground somewhere. Can't be more specific because I have no idea how you wired it up.

Alternate idea: fuel pump has gone bad and is suddenly drawing multiple times more current than it would ordinarily require to run it.

 

I reused the purple/white wire that switches the relay and reused the hotwire from the stock pump to drive the new carter external pump. Maybe the carter uses an extreme amount of current to run? what could be back feeding through the relay? Like I said, I took the pump out of the equation by unwiring it and just switching the relay caused the fuse to blow. Must be a short somewhere, right?


Why would the 20amp fan fuse pop before the 3 amp fuel pump fuse?

 

I just put a new high pressure fuel pump in my sons 89 z28 i rock. i ran a new wiring harness that was bigger wire. ran hot wire to alternator hot side.wired up factory harness for gauge. installed a new relay in rear of car. fired up and is running. hope this helps.

 

Hi liftem, I see your new here, welcome to TGO. As a point of future reference, you may want to check the dates of the threads you respond to, the thread you just bumped is from 2015, and in the seven years since I'm betting the guy has got his fuel pump sorted .

Lastly, your Son has an "IROC" , as in "International Race Of Champions" , and not an "i rock" , , , notwithstanding whether or not you, or he, actually do in fact, rock......