strange problem with fuel pump, and question about the harness

[SPOT MY 6]

I have a strange problem with the fuel pump. I have a hot wire kit which has a 14awg wire running from the alternator all the way to the back of the car to a relay. The factory wiring harness plus into the relay, then the fuel pump plugs into the harness that is coming out of the relay. Everything works fine. But when I disconnect the fuel pump from the relay, turn the relay on, and jumper only the power wire (so the middle wire and the ground wire are disconnected), the fuel pump turns on at like 20% power. As soon as I jumper the ground to the harness, the pump powers up like normal.

Why does the fuel pump turn on when ONLY the power wire is hooked up? I have a double pumper setup and for some reason the other pump in the tank doesn't work like that. Only the primary pump that is wired to the factory harness is goofy.

Thanks.

 

[unix_punk]

ground

I'm pretty sure it turns on because its somewhat grounded to the tank already. u figure the locking ring on the hanger touches the tank, and the tank touches the body... racetronix hotwire kit has an additional ground that goes on the hanger inside and a ground that actually clips on the tank itself. 14ag wire seems kinda small. u know who made that harness? I'm pretty sure racetronix's is at least 12, maybe even 10.

 

[SPOT MY 6]

Ok I think I might know the problem. The pump is to the hanger on the inside of the tank. The ground wire from the factory harness is fastened to the top of the hanger on the outside of the tank. My guess is that the hanger is touching the floor of the car which is creating a very weak ground. I am going to pull the tank down and try rewiring the ground.

 

[SPOT MY 6]

unix_punk, looks like we posted at the same time.

The hotwire kit was purchased a long time ago from Modern Musclecar (now Full Throttle Speed). Yes I am sure it is 14awg. I may consider upgrading it to something larger though so I will check out the racetronix kit. Thanks for your reply.

 

[unix_punk]

oh yea, one minute off. the extra ground inside the tank comes with the walbro from racetronix, im not sure if you can buy just the extra in-the-tank wires seperate or not though.

Grand National PnP Fuel Pump Upgrade Harness