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Best way to wire fuel pump for carburetor

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mc1984ss
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Best way to wire fuel pump for carburetor

Post by mc1984ss » Mon Oct 21, 2019 9:30 pm

I've finally started working on my car a little bit after many years. I will be using an electric fuel pump ( no boss on block) and a carburetor with a bypass regulator. What is the best way to wire this? Should I use the Holley oil pressure switch so it is only on when there is oil pressure? The only problem I see with this is if the float bowls ever go dry for what ever reason the car won't start because the fuel pump won't turn on. I'm trying to eliminate a manual switch and am wondering what the best way is. Thanks in advance. Also is there another option for the oil pressure switch besides the Holley one? I think it's about $30
1984 Monte Carlo SS
454 w/ mild hydraulic cam
Edelbrock Performer RPM Air Gap intake
Holley 800 double pumper
Hooker super comp headers and torque tech 3" true dual exhaust
th-400
12 bolt w/ SSM lift bars, 4.10 gears, moser axles, c-clip eliminators, and brute force limited slip. ta cover
Weld pro stars and Harwood fiberglass hood

Damon
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Re: Best way to wire fuel pump for carburetor

Post by Damon » Fri Oct 25, 2019 1:47 pm

I've always run them off the "IGN" terminal of the fuse block. It's hot in both the Run and Start positions. I tried the oil pressure switch thing once but the sometimes long cranking thing is real. And, lets face it, by the time oil pressure drops the damage is pretty much already done, especially when you consider the motor will keep running for some period of time just off what's left in the bowls.

Depending on how many amps your electric pump draws, you may or may not even want to use a relay. Yes, everyone says use a relay, but my experience is that it's just added complexity and one more potential failure point. I use an ancient Carter Street Pump as a booster to my block-mounted mechanical and it draws practically nothing- like 2.5A. Even something like a typical Holley Blue fuel pump only draws about 3-4A. We are definitely not in a power range where you need the power switching capability of a 30A cube relay and big wires. Some 12ga wire run back to the pump and a female spade connector shoved on the open IGN terminal of the fuse block has worked for 12+ years for me without a single problem.

Now, if you're going racing and your car requires a battery disconnect switch on the rear bumper, obviously you need to wire it such that the electric pump turns off as well when you hit the kill switch. But again, there is no requirement for a relay to trigger the pump that I am aware of.
78 'Amana White' Malibu- My grandmother's go-to-church car with 35K original miles. Out with the smogger 2bbl 305. In with a really mild 383 topped with ancient AFR heads, Summit's finest K1103 house brand flat tappet cam, a Weiand 142 "underhood" blower and a home-brew QJet. GN rear, DRs. 11.85 @ 116. Nitrous coming.

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