How to Fix a Lawn Mower Fuel Pump

What You'll Need
Pliers or adjustable wrench
Small brush

As anyone knows who has had experience with gas engines, a fuel pump performs a vital function in keeping the engine running properly. Without an efficient fuel pump, your lawn mower engine will either run rough or will not run at all. The cause of fuel pump inefficiency will typically be a clog or damaged to the pump. In either case, you should be able to repair the pump in less than two hours. By following the steps below you will be able to unclog your fuel pump, repair it, or replace it and soon have the mower running as good as new.

Step 1 – Locating the Pump

You will be able to quickly locate the fuel pump. It has two small rubber tubes connected to it. One connects to the gas tank, and the other to the engine's carburetor. The pump will be mounted on the mower, near the gas tank. On some mowers the pump is powered by an electric current. If you find an electric wire connected to the pump, chances are, the pump is one of those that is powered by electricity. If it is, you should use a voltmeter to verify that it is getting electrical power.

Step 2 – Testing the Pump

Before assuming that your mower's fuel pump is defective, you should perform a quick test. To do this, disconnect the fuel line from where it is connected to the mower's carburetor. Turn on the power supply and check to see if gas is spurting from the fuel line. If it is not, the problem is most likely in your fuel pump.

Step 3 -  Inspecting the Pump

Remove the pump from the mower, using a wrench or pliers, and a screwdriver. Disassemble the pump by carefully removing screws that hold its parts together. Be careful not to damage seals or gaskets. Once you have the pump open and are able to see its various parts, look for damaged, broken, or bent parts. Next, look for foreign matter such as sand or gasoline resin deposits that could be gumming up operation of the pump. If you find resin deposits (a brownish color), spray surfaces with resin solvent and let it sit for 10 minutes to dissolve the resin. Then wipe the resin off with a clean cloth. Remove any particles of sand or debris using a small, soft brush or cloth.

Step 4 – Reassembling the Pump Parts

Put the pump parts back together, replacing any gaskets or seals that became detached. If gaskets or seals are damage, you'll need to replace them before completing the assembly of the pump's parts. Attach the pump to the mower and connect electrical wires and all fuel lines except the one between the pump and carburetor.

Step 5 – The Final Test

Follow the same procedures you used earlier to test the pump. Once you have turned on the pump's power supply and can see fuel being pumped out of the detached fuel line, you'll know your repair job was successful. Finally, replace the fuel line used for testing, and start your mower.