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This is a quick test to see if your accelerator pump is working. This test will work on most engines.

Watch a video:
Accelerator Pump


  • Warm up your engine
  • Turn it off
  • Remove air cleaner
  • Choke valve should be open - if not it could be stuck on the fast idle. Open the throttle a small amount which may allow it to open.
  • Pump your throttle to wide open watching the inside of the carburetor bore.
  • You should immediately see a stream, or streams of gas squirting in the throat. 1 barrel will have 1 stream, 2 & 4 barrels will have 2 streams. Some 4 barrels will pump gas in both primary & secondary bores. These will have 2 accelerator pumps.

This test cannot be done accurately when the engine is cold. The carburetor may not have the proper amount of gas in the bowl. This test is being done while the carburetor is on the engine. We have other tests you can perform while the carburetor is on the bench with the top off.

Squirt is weak, or none at all.

  • Main discharge could be missing the check valve (check ball, or check weight)
  • Passage from the pump well to the main discharge may be plugged.
  • Accelerator pump well may not be filling up completely.
    • Check valve is dirty, or missing (check ball usually). Some carburetors don't use a check valve. They are filled over the top of the accelerator pump well.
  • Accelerator pump deteriorated, or it's the wrong pump.
  • Accelerator pump installed incorrectly.

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