Testing a Stovebolt Fuel Pump


  • Disconnect the fuel line at the carburetor and attach a length of rubber fuel line long enough to reach over to the fender, or somewhere similar. Start the engine and let it idle - - - - - it will run on the fuel in the float bowl for a while. In 30 seconds at idle, it should pump at least a pint of gas.
    Now you have done the first of three tests - - - don't stop now.
  • Attach a pressure gauge to the line you removed from the carburetor - - - clamp it if necessary. Run the engine for a few seconds. You should see somewhere between 2 and 4 pounds of pressure, and this is important - - - - the pressure should stay there for several seconds after you shut the engine off. There is a one-way valve in the pump that prevents back flow.
  • Now, attach a vacuum gauge to the inlet side of the pump. Run the engine. You should see 10 inches of vacuum or so, and it should also stay put for a few seconds after shutdown.


If the pump can pass the pressure and vacuum tests, but is low on volume, start looking for a restriction between the pump and the fuel tank, or a clogged pickup tube in the tank. It's also possible to have an air leak in the flex line between the frame and the pump that will suck air but won't leak gas.

Good luck!
Jerry

Jerry “Hotrod Lincoln” Herbison

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
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