Help me fab a fuel pump circuit

[just plain john]

I have an idea for a fuel pump circuit and would like some feed back. I propose to take 2 #10(fused + and -) wires directly from the battery down the frame rail to a frame mounted relay. I'm going to trigger it with the factory wire extended to the new relay location. I'll switch the positive with the relay and use the negative for a known good ground. Sound about right? Before anyone asks, there is no circuit to begin with in this hybrid build so a hotwire won't help. So what components would be needed? Fuel pump pulls 30 amps, right? Any guesses if battery voltage would be adequate at the pump with this method? Discuss...

 

[sykegn]

I would mount the relay under the hood.I wouldn't bother running a grind wire back, instead I would run a good ground to the frame. Insuring that you have a good ground for any components that are grounded to the frame. Keep it simple.

 

[GNVenom]

You won't need anything larger than 12 gage wire. The fuel pump won't draw 30 amps - more like 16 amps at it's highest load - and the voltage drop at that current is negligible using 12 gage wire.

Besides, the relay terminals you will use for the 30 amp relay can't handle 10 gage wire.

I'd recommend you use a sealed relay and connector for anything outside of the passenger compartment.

 

[just plain john]

Thanks for the reply John. I'm curious though, would there be a need for a hotwire kit in this application? The donor car gave up it's factory fuel pump relay, but as I noted there was no circuit in the car originally. Would using this relay directly to the pump diminish voltage? Should I build the circuit like the factory set up and use it to trigger your hot wire kit, or is battery voltage adequate?

 

[GNVenom]

You can use the trigger from the ECM to fire any relay you use. No need for a hotwire kit since you're using larger wire from the start.

One word of caution; IMPO, I'd never use "used" relays. I wouldn't leave that to chance since you don't know the condition of the relay. It is a mechanical device with silver contacts, which are subject to wear and tear. Also, the factory relay is not sealed; it was originally treated (25 years ago) with tar sealant, which has long ago broken down.

 

[just plain john]

Thanks or your advice. I'm looking at some of your products as we speak. Couldn't trade a never used Caspers hot wire for a store credit could I? Didn't think so...

 

[GNVenom]

Heh, put it on Ebay...they sell for more than list price there!