Electric Fuel pump question?

Shakin66 · Nov 5, 2005

Holley's instructions say that the pump should have power that is only on when the engine is running. I had planned on using my sound system's "switched" power but now I'm back to square one. I am not as good on electrical issues as I want to be so I dont know where I can find "running" 12 volts. I am guessing the alt. but I have issues there also since I am switching to serp. drive and dont know yet how to wire up this newer alt. Does anyone know what mods would be needed to run a one wire alt?

Soaring1 · Nov 5, 2005

No need in running a one wire alternator. Just hook up your fuel pump to the key cylinder positive switch.

Shakin66 · Nov 5, 2005

But is that switched power? If so that will be much easier than I was thinking. I also have a enertia switch to wire in.....Too many projects ...Not enough time!

10secgoal · Nov 5, 2005

Don't really want that. The ignition can't hold alot. But you can use it to turn on a relay.

Shakin66 · Nov 5, 2005

See there you go leaving me in your electrical "dust"
I can built a engine but I have NO knowledge of all things electrical. The relay just acts as a switch right?

65ShelbyClone · Nov 5, 2005

You need a relay and an in-line fuse for the pump power. The relay is in fact a switch, but it uses a low-amp solenoid to close a high-amp circuit(like a starter solenoid; the key couldnt possibly handle the power of the starter). It allows you to have a flimsy switch control alot of amps.

What you do is wire the relay's low-power trigger to the key so it "clicks" when turned to "ON". Then run a wire off the battery positive side and through the relay's high-amp poles and then on to the pump. I used a 7.5A mini blade fuse for my pump.

Shakin66 · Nov 5, 2005

Hmmmm, Is your pump on switched power? Or is that term on the switch only powered when the engine is running?
Sorry for all of the questions...

65ShelbyClone · Nov 5, 2005

Thats what the forums are here for, right?

I did the cheap way out on my pump wiring; my relay gets power from the neutral safety switch wiring(no automatic anymore) which is turned on at both the "ACC" and "ON" ignition switch positions(no listening to radio with the engine off otherwise the pump runs). I should wire it off the key-on circuit. I dont know that there actually is a circuit that gets power only when the engine is running. EFI cars have them, but I dont know about our old stuff.

67coupe351w · Nov 5, 2005

This might help:

Shakin66 · Nov 6, 2005

Thanks for the help, I am wondering if this pump is going to work or not with this carb set up. I bought it with fuel injection in mind. I am worried about it flooding the carb even though I have a Holley regulator installed. I may just install a oil pressure safety switch which would have the "running" power I am looking for.

iskwezm · Nov 6, 2005

Shakin66 said:
Thanks for the help, I am wondering if this pump is going to work or not with this carb set up. I bought it with fuel injection in mind. I am worried about it flooding the carb even though I have a Holley regulator installed. I may just install a oil pressure safety switch which would have the "running" power I am looking for.

why would it flood the carb?Just regulate it down to about 6-7 psi.Do you have a boost referenced regulator?

66Runt · Nov 6, 2005

Fuel pump runs with key on is different than Fuel pump runs with engine running

Things like accidents, stuck floats, etcetera, is why they want you to wire the electric fuel pump so that it only functions when the engine is running.
A simple way is to run the relay through the Normally Open side of a SPDT oil pressure switch or a Normally Open vacuum switch, and add a bypass lead for "Start" mode. Very easy to do, and is much safer. Really don't even need the starter bypass lead with a carburetor, unless you let your car sit for weeks at a time.

Anybody ever make tech for an open-track event w/o having their pump wired up that way?

Scott

Shakin66 · Nov 7, 2005

I am gathering the fittings to use my oil pressure shut off switch to activate the fuel pump. "Iskwezm" As far as a boost referrenced regulator? I am running a Holley PN 12-803 but I am unsure what you are talking about but sounds lilke presure raises with boost. What regulator are you running? and do you still have the Radiator for sale?

10secgoal · Nov 7, 2005

What he means is if you have a fuel pump for EFI, the pressure is alot higher than that of a carb. A carb regulator will have a helluva time knocking the psi down unless it has a return system.

84convertablegt · Nov 7, 2005

what fuel pump are you running? also, the fuel pressure cut off switch is the best idea. Then you know you are wired correctly and you can sit all day with the car in the on position without the fuel pump running. you dont need a start bypass with a carb, there is plenty of fuel to get running and get oil pressure unless the motor is crap and you dont have a choke i would be careful running a efi pump with a carb, its not the flow but the pressure thats gonna be a problem. efi systems are made to run at atleast 30-50 psi and thats regulated. the pump may be higher, and im not sure that a carb regulator is capable of keeping the pressure at 6psi with an efi pump. usually theyd be knocking down max 15 psi to 6psi, and the best way is with a return line, otherwise you are backing up alot of fuel and making some serious pressure in your fuel lines. they may just burst under that amount of pressure. just a thought....

iskwezm · Nov 7, 2005

Shakin66 said:
I am gathering the fittings to use my oil pressure shut off switch to activate the fuel pump. "Iskwezm" As far as a boost referrenced regulator? I am running a Holley PN 12-803 but I am unsure what you are talking about but sounds lilke presure raises with boost. What regulator are you running? and do you still have the Radiator for sale?

i have a Paxton 4 port regulator which is 1:1 boost referenced,so for every lb. of boost it raises pressure,so if you run about 6-7 psi,you will need a pump capable of 15+ lb's of fuel pressure.
yes, the radiator is still for sale

Shakin66 · Nov 7, 2005

Just got off the phone with Holley's tech guys and the "black" pump I have is a Fuel injection pump and since I am planning to eventually F.I. this thing he suggested a Mallory return line Regulator. I am glad now I asked and thanks for the advise. I am interested in the radiator but if you are running hot I may be also with our combos being faily close.

iskwezm · Nov 7, 2005

Shakin66 said:
Just got off the phone with Holley's tech guys and the "black" pump I have is a Fuel injection pump and since I am planning to eventually F.I. this thing he suggested a Mallory return line Regulator. I am glad now I asked and thanks for the advise. I am interested in the radiator but if you are running hot I may be also with our combos being faily close.

honestly,i have always had "running hot" problems,and this radiator did help the N/A 289 i had,but didnt work with the new engine,I REALLY need the money,but if your going with a s/c,then it might not be for you,but i have seen people use it and it worked fine

maybe i've had bad guage this whole time

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