Electric fuel pump

There are several pumps that allow fuel to be pulled through the check valves by the mechanical pump. This type of pump is what I call a ‘vibrator’ or oscillating pump. It functions by having an electric magnet coil that when energized pulls a piston down a cylinder, against a spring, pushing fuel. Once the piston reaches it’s full travel, a switch is opened, which breaks the current to the electric magnet, which allows the piston to be pushed by the spring back to it’s original starting spot.

Not all of the vibratory pumps use a piston, some use a diaphragm. But the back-and-forth motion is common to this type of pump .

These pumps make a noise and vibration to go along with their function.

Also, the ability of the electric magnet to pull the piston, or move the diaphragm is often too weak to overcome a bit of varnish from old fuel, or from a bit of dirt or rust flake that has made it into the pump. A good filter before the pump is mandatory.

The Carter motor-type, rotary-vane pump is what I prefer. The motor has far more starting force to get a sticky pump turning, and pumping than the vibrating magnet type. AND, since the usual reason for an added electric pump is to prime a dry mechanical pump and/or dry carburetor, the positive-displacement type of rotating-vane pump is more effective at moving air, as well as fuel through the pump. This type of pump has a ‘whir’ noise associated with the electric motor spinning.

BUT, because of the nature of a rotary-vane pump, it’s able to block fuel flow through it’s pump, There are positions where the pump will allow fuel to be pulled through, but it also can block fuel flow. To allow this type of pump to be used as a priming pump, and secondary to the engine’s mechanical pump, a bypass valve and circuit must be installed in parallel with the pump.

A ‘Tee’ is put in the line just before the pump’s inlet, and a matching ‘Tee’ is put in the outlet line after the pump. These ‘Tees’ are connected with a line with a one-way check valve. The check valve is installed so that the mechanical pump can pull it open, letting fuel from the inlet line flow to the outlet line, which supplies the engine’s mechanical pump. When the electric pump is used, the check valve closes, preventing the fuel in the lnes from just making a continuos circuit around the pump. These check valves open with about an ounce of suction, so there is very little to no restriction to fuel flow.

Usually, priming pumps are mounted near the fuel tank, where they are not visible unless you are under the car. This also functions to reduce the noise made by the pumps in the passenger compartment.

If you are adding an electric pump to your car, it is suggested that the factory fuel line, which usually is fastened to the inside of the right [passenger side] frame rail, be relocated to the outside of that frame rail. This keeps the steel frame between the fuel line and the heat from the exhaust pipes and muffler. Vapor lock is a very common occurrence with our ethanol-tainted gasoline, and the suction in the fuel line from the engine’s mechanical pump. I usually relocate the fuel line to the outside of the left frame rail, this keeps the line in the

coolest location under the car. All the hot air pulled through the radiator, and over the exhaust manifold either leaves the engine compartment by the hood’s doors or louvres, or is exhausted under the car, which means that the two frame rails act as sides to a ‘duct’ for heated air..Just touch the wood flooring under the carpeting or under a seat cushion after a 20 minute drive in 90* weather: the floor is about 120-140*.

Hope this helps.. just google or ebay search for 6v electric fuel pump, and you will find sources and part numbers. Carter makes the motor driven vane pumps, I don’t know the manufacturer for the vibrator pumps, but my local Car-Quest auto parts store has them available.

Greg Long

I’m sure many know better than I, but you want very low pressure, in the 3 to 4 psi range. You can buy pumps with that low pressure rating.

The little chrome pressure regulators sold in auto parts stores are junk. If you must put a regulator in line, buy a quality unit.

Also, decide how to wire the pump correctly, I just heard the story of pulling power through the ignition system, drawing too much current from the system and causing issues with engine.

Make very sure you have a positive way to cut off the fuel pump in an emergency. I had an engine fire in my ’31, thought I’d turned off the pump, but didn’t….and the results were bad, luckily not disastrous. I run only a mechanical pump on it now for that reason, may take a few more turns of the engine, but that’s how it was done back then and that’s good enough for me…..

Greg I like your idea of running the line outside of the frame on the passenger side. Do you have a recommendation on where the line starting at the tank goes leaves so that its not affected by a stone that might impact it off the rear tire? Where specifically would you recommend going back in to the engine compartment to the mechanical pump?