[briann]

I have never run a fuel pump relay on any of my cars (race and street ones) in over 33 years and have never had a mishap or problem.

I just put a new electric pump on the car and noticed this car has 14 gauge wire from the +bat to toggle switch (which is rated plenty at 40 amps) and then 14 ga toggle to fuel pump in rear of car and I know fuel pump wiring should be 12 ga usually unless its a really short run. So I was just looking for some opinions if I should ditch the 14 ga wiring and go with 12 ga instead. Or go with a relay now which of course is all the correct 12 gauge wires anyway but just a tad more time putting one in.

Since this car never had a problem with the 14 ga thats in there in over 30 years I guess I'm looking for reason to get in, under and sideways and such to replace the wiring with 12 ga or go with a relay which ive never needed before.

[george kujanski]

The larger ga. wire will produce less voltage loss to the pump, especially since it's in the rear of the car. Search for wire tables on the 'net and find the ohms per foot for 14 ga. wire. Multiply the ohms per foot times the length of wire that you have; that'll give you the resistance on each leg (Pos and neg.) of the run. Multiply the resistance in each leg times the rated current draw of the pump. That'll give you the voltage loss in each leg.


You probably want no more than a 2 volt loss to operate the pump properly. I f more than 2 volts, up the wire size to the next ga.

George

[Jagtec1]

I would certainly use a relay. You can use small (14-16) wire to trigger it, but I would use 10-12 on the power leg. Ensure a good ground with 10-12 also. The longer the pump runs, and the addition of heat (whether ambient or otherwise) will increase your potential voltage drop. Better to have too much than not enough when it comes to wiring.

My$.02

["QUICK-SILVER"]

If all you need is a good reason?
Safety
Function
Modernization
Something to do if nothing else.

[briann]

Well I decided to wire up the relay and after it was all done the relay didn't even work. Went to 3 different places to try and find a new relay part to replace bad one with and none to be found that would match up with it. Since I needed to drive the car this afternoon I took it out and rewired it all with 12 gauge right off the remote solenoid to toggle switch then to pump and a fuse and all is well and fine. Checked for voltage drop test and its fine. Worked fine this wired this way for last 30 years with 14 ga so I'm just leaving it now.