How do I find, fix and install a lawn mower fuel pump?


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What Is a Fuel Pump & Where Is It Located?

A fuel pump is used when the gas tank is mounted lower than the carburetor and gravity cannot be relied on to carry gas through the fuel line. Briggs & Stratton pulse type fuel pumps have either a plastic or a metal body and develop pressure using the varying vacuum in the crankcase, which is created by the motion of the piston and the operation of the crankcase breather. A fitting on the crankcase cover or the dipstick tube draws the pressure to pump the fuel.

Where can you find the fuel pump in your small engine?

The fuel pump is typically mounted in one of four places:

  1. On the carburetor

  2. On the engine

  3. Near the fuel tank

  4. Between the tank and carburetor

How to Check Small Engine Fuel Pumps

On a normally operating fuel pump, there should be no gasoline present external of the pump or in the pulse line.  If there is fuel present in these locations, or if the pump is simply providing fuel to the engine, then follow the steps below to inspect and replace the pump.

 

  1. Turn off the fuel valve (if equipped) at the base of the tank where the fuel line is attached. 

  2. If there is no fuel valve, stop the flow of gas using a fuel line clamp.

  3. Loosen the mounting screws and remove the pump from the mounting bracket or carburetor.

  4. Check for hairline cracks and other damage to the external surfaces of the pump. 

  5. If it is damaged and has a metal body, discard the pump and perform a fuel pump replacement.

How to Fix a Fuel Pump on a Briggs & Stratton engine

  1. With the fuel valve closed or the line clamped, remove the mounting screws.

  2. Then, disconnect the fuel hoses using needle nose pliers to loosen the clips.

  3. Remove the screws and disassemble or replace the pump.

  4. Inspect the body for cracks or other damage. Soak metal parts in all-purpose parts cleaner. The pump body may be soaked for up to 15 minutes.

  5. Check the hoses for cracks, softening or hardening, and replace any worn parts.

  6. Discard old gaskets, diaphragms and springs, and replace them with parts from an original manufacturer's repair kit.

Installation Instructions for Fuel Pump Replacement

  1. Place the diaphragm spring and then the cup over the center of the pump chamber. Also insert a valve spring.

  2. Install the diaphragm, gasket and cover and attach with pump screws. Tighten the screws using a torque wrench.

  3. Attach the pump to the carburetor or mounting bracket, using the pump mounting screws.

  4. Always run the engine after new pump installation or repair to verify that there are no leaks.

Different pumps will include some variants in the part configuration, but these basic instructions can guide you through installing the replacement fuel pump. Round fuel pumps are one of the most common variants. It cannot be repaired, only replaced.

You can also check out our Fuel Pump Replacement PDF for more guidance in replacing this small engine part.

For more information about your fuel pump, contact a Briggs and Stratton Dealer.


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