Fuel pump wiring, will this work???

[dsmputz]

Allright here's the scoop, my buddies turning his 91 GSX into a poor mans drag car. We just recently got into an argument over the way he wants to wire his fuel pump. He bought a fuel cell with a walbro 255hp and ran -8an ss braided lines to the the fuel rail and back. His battery has been relocated to the hatch (in a sealed box with the disconnect switch out the back) and wants to run his fuel pump right off the battery using only a toggle switch on the dash to turn it on/off. Keep in mind that there is a fuse on the power wire to the pump but it sounds pretty unsafe to me. Like what happens if he's in a crash on the street (he plans on driving it on the street every once in a while) and nobody knows how the hell to turn off this pump thats spewing gas all over the place. Have any of you guys gone this route before??

 

[dsm-onster]

Drag car vs. street car. which is it?

Why not do it right and add a relay for the stock wiring to control. What's the difference in voltage?

 

[dsmputz]

The car is 95% drag with a cruise down the main strip every other sunday. I don't know much about electrical but I can't see there being a difference in voltage.

 

[GVR4592]

It should be wired so the kill switch cuts power to the pump, if he wants to use a switch then that's his choice.

 

[eclipsh]

Why not just do the standard rewire with the relay in the back and wire the kill switch into the ground for the relay. It'd be stupid easy to do and safer. I cannot think of a single reason not to do it other than being lazy.

 

[GVR4592]

Why not just do the standard rewire with the relay in the back and wire the kill switch into the ground for the relay. It'd be stupid easy to do and safer. I cannot think of a single reason not to do it other than being lazy.

The kill switch has to be wired to the positive side of the electrical system.

 

[eclipsh]

The kill switch has to be wired to the positive side of the electrical system.

Oh, is that a rule? I think you could argue it is on the positive side since by turning off the relay you are interrupting the positive wire, not the negative.

To put that more clearly, the cut switch is interrupting the ground for the relay on the positive wire, not the ground for the pump, and is therefore a positive-side kill switch.

 

[project_tsi]

Yes, its an NHRA rule that the switch must be wired in the positive side.

 

[dsm-onster]

The car is 95% drag with a cruise down the main strip every other sunday. I don't know much about electrical but I can't see there being a difference in voltage.

I can't either. So there's no benefit of increasing the fuel pump flow. There's only the risk of fire and getting caught breaking the NHRA rules; all for going the easy route.

 

[steve]

The kill switch has to cut power to everything so the fuel pump has to connect after it for the power feed. The Relay for the pump is still the right way to go and continue to use the factory wire to the pump to trigger the pump so you keep the minimal protection against running the pump after the engine stops.

What your talking about now is pretty much a normal rewire but with the battery in the back the new power feed is really short.

Steve