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204 East 15th Street

Eldon, Missouri 65026

 

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Electric fuel pumps, regulators, and older vehicles

 

There are a number of reasons car enthusiasts look at electric fuel pumps. The most common being hard initial starting due to modern fuel evaporating from the carburetor overnight. Whatever the reason, there are a number of considerations when deciding to install an electric fuel pump:

 

(1) Is the installation legal? Electric fuel pumps should be installed with the permanent wiring activated by something like an oil pressure switch, such that in the event of an accident and the driver becoming incapacitated, the electric fuel pump would automatically be turned off. Temporary wiring to a push button can be used to activate the pump and fill an empty carburetor. Release of the pump button will kill the pump, but there will be sufficient fuel in the carburetor bowl to start the engine and run until the oil pressure comes up to activate the permanent wiring.

 

(2) Does the pressure produced by the pump fall within the parameters required by the carburetor? This question has more than one issue and should be considered carefully. Think of the difference in methodology of the electric pump vis--vis the stock mechanical fuel pump. The electric pump is more or less a constant pressure, constant volume pump (assuming the GPH of the pump is greater than the maximum demand of the engine). The stock mechanical pump is driven by the engine; therefore volume, and to a lesser extent, pressure, is a function of the RPM of the engine. Thus it is quite possible, if the wrong electric pump is chosen, to have a pump that floods the engine at idle, and has insufficient volume to maintain proper carburetor bowl lever at wide open throttle.

 

(3) Because of (2) above, many enthusiasts opt for an adjustable inline regulator. Many of the less expensive regulators regulate pressure by regulating volume. Thus getting the pressure sufficiently low to not flood the engine at idle then limits the volume necessary to drive the vehicle at highway speeds. And just because the dial on the regulator states some number, do NOT ASSUME that the output pressure from the regulator is what the dial indicates. ALWAYS check the output pressure with a calibrated fuel pressure gauge. A return fuel line from a connection just before the carburetor back to the fuel tank is MUCH better at reducing idle flooding than a regulator.

 

Summary the electric pump IF properly selected and properly installed, may be of benefit to the enthusiast. Do it wrong, and one had better check with their insurance agent about fire BEFORE installing the pump!