How do I wire an electric fuel pump

[louie the fly]

I've seen things on the web about wiring an electric pump into an oil pressure sender, or through a relay, and so on. What's the easiest, &/or best way to wire a pump? I want it to be safe so it will need to cut out if the engine stops. But it's obviously got to supply fuel when cranking. I plan to gut the original mechanical pump and just pump fuel through it. To keep it looking proper, you know...

[chopt50wgn]

1st thing is you want to use a relay for the pump. You can wire it up to a switch that you turn on from inside before you start the motor or have one wired to the ignition so when you turn the ignition on the pump runs.

I don't know if gutting the mechanical pump would be a good idea. The gutted pump may not allow the flow from the electric pump to be a steady flow.

[Cpt.Fred]

a few folks here run electrical pumps through their mechanical ones without problems, if i recall correctly.

then again, most people only use them for starting aid and switch them off afterwards, now running mechanical only.

the setup you mean is quite complicated,

when i put my electrical pump in i wanted it to be like that as well but found it impossible to stay on a 6V system.

to be honest, i still haven't fully understood how these "kill" relays work...

so now i am running electrical only

(original pump was broken, so i just took it out and fabricated a metal cover for the hole in the block)

through a switch under my dash and from there to the ignition.

works fine and since i have it working on low pressure i don't even need a return line.

[greg g]

you can pick up a hot terminal on the ignition side of the coil. That way it is only hot when the ignition is on (and you don't need to crawl up under the dash to access it. You can power the pump direct through an illine fuse or power the relay from there.

I might still put a toggle switch in the circuit. There is a hole in the far left end of the dashboard under the lip near the hood release cable. That way if you need to run the carb out of fuel and shut the pump off as a rudimentary anti theft device.

[desoto1939]

I have a 39 Desoto and have a toggle switch setup on my car to runthe electric pump. The wire comes off the iginition switch to the toggle switch and then to the pump.

i still have the mechanical pump on the car. The electric pump is a backup to the mechanical and also is used to prime the carb after it has sat for awhile. Keep the mechanical pump and do not gut the pump. The electric will pump the fuel throught the mechanical pump. So when I turn off the key on the ignigition switch the electric pump is also killed. So there is not battery drain onthe car and also this eliminates the issue of the pump still running after the engine is off.

Rich Hartung

Desoto1939@aol.com

[builtfercomfort]

I have a feul pump relay on the ignition circuit, and rather than adding an oil pressure switch I found a Ford rollover / collision switch off a F150. It shuts off the pump on impact. I forget the accurate name of the switch; it was $10 from eBay. (

[Kevinb71]

Here is a diagram from a Holley book I have. It would shut the pump off when oil pressure drops, but would run the pump when cranking.

fuel pump.pdf

[55 Fargo]

Whats up with all the complications of wiring in an auxillary/emergency electric fuel pump?

Am I missing the point, I thought it would be wired from the igniton swtich to a toggle swtich, maybe an in-line fuse to the fuel pump, and thats about it.

Anyone care to enlighten me on this topic....Fred

[teardrop puller]

No one wants fuel still spewing out if you have a wreck. So the Ford rollover/collision switch or an oil pressure switch is necessary when you run an electric pump.

I would use a push button switch in parallel with the solenoid switch to prime the carb if needed. Push button is good because you can not forget to turn it off.

kai

[Don Jordan]

Wow! I didn't know it could be so complicated. I just ran a wire from the pump to the ignition. Turn on the key it turns on the pump. I would hope if I get into an accident I would be able to turn off the ignition. I had always thought about putting the fuel pump on a switch but not because of an accident but a cheap anti theft device.

[Mustang6147]

In street car application, I always wire them to a circuit that is hot only when they key is on.

In race application, I give the pump its own switch on a panel...

There is no need for a relay unless you are runnin a huge pump. 15 amps is enough, but I run 20 or 30 amp fuses. Just use the proper wire, solder all connections, and use shwrink tube, because over time a corroded connection will cause a bigger amp draw.

[55 Fargo]

In a rollover or major wreck, I think most of us would be toast, not to be negative or discount safety. I would not think anything would help much in these old girls in a major wreck, perhaps I am wrong about this, and am all ears if my opinion is incorrect....Fred

[55 Fargo]

In street car application, I always wire them to a circuit that is hot only when they key is on.

In race application, I give the pump its own switch on a panel...

There is no need for a relay unless you are runnin a huge pump. 15 amps is enough, but I run 20 or 30 amp fuses. Just use the proper wire, solder all connections, and use shwrink tube, because over time a corroded connection will cause a bigger amp draw.

I agree, this is how I would do this wire-up, if and when I ever install an electric fuel pump on my 47.............

[58Regent]

I like the idea of having the pump on a pushbutton for priming the carb only and stick to the mechanical pump when the engine is running. Would fuel still flow through an electric pump if it's not running?

[Mustang6147]

I like the idea of having the pump on a pushbutton for priming the carb only and stick to the mechanical pump when the engine is running. Would fuel still flow through an electric pump if it's not running?

In short, you have to check the pump you choose to buy, to know about its bypass or relief/ flow... More importantly, Will the electric pump burst the diaphram of the mechanical pump? I say if the preassure is to high, Yes

I dont know what engine your runnin, but on my flathead, I run a low pressure pump. 3 to 5 psi. Dont run anymore then 7 at an idle or engine off pump on. And going down the freeway you dont want to drop lower then 5 1/2 psi...That is based on a current v8. Drop down 2 psi on both sides for a flathead...5-3 1/2

respectivly

[james49ply]

i have thought of installing one on mine, but to push the fuel through the origional pump under pressure??? if the diaphram leaks, fuel will go into the engine, and toast everything. maybe for a prime to the carb, then shut it off, that seems like a good idea

[Rollie���]

The replacement fuel pump that was installed less than a year before I bought my car failed within a month of me getting the car on the road. I bought a 6v electric pump, mounted it lower than the tank on the frame, wired it to the ignition switch, took the lever off the mech. pump and made a block off plate (so no fuel could get in to the block), and have been driving happily every since (minus the down time for the motor rebuild).

[louie the fly]

Thanks all for the ideas and opinions. Once I get some time to work on my car again I'll sort out what I'll do. Pro's & con's of all ideas here I think.

Cheers