Small Engine Repair: Checking Fuel Pump Diaphragm & Inlet Needle on a Diaphragm Carburetor
**Always follow the instructions in your repair manual when doing repair or maintenance work on Outdoor Power Equipment. Manuals can be found at the manufacturers website.**
In this video I show how to check the fuel pump diaphragm and inlet needle for leaks on a diaphragm carburetor. A diaphragm carburetor is used on hand held power equipment, and are popular because they will work in any position. All chainsaws, trimmers and blowers that I have seen use a diaphragm carburetor. To check the fuel pump and inlet needle, pressurize the carburetor to 10 psi through the fuel inlet. The carburetor should hold the pressure fairly steady, and if it doesn't than there is a leak around the fuel pump diaphragm or inlet needle. You can pin point the leak by dunking the carburetor in water while it is pressurized. If the leak is around the fuel pump diaphragm, than either the fuel pump diaphragm, fuel pump diaphragm cover or the body of the carburetor is at fault. If the leak is coming out of the venturi, than the inlet needle or seat is faulty.
- 3/8" wrench to remove carburetor
- Mityvac to pressurize the carburetor
- Needle Nose plyers
- Carburetor should be pressurized to 10psi through the fuel inlet. Never exceed 10psi. Its important to run fuel through the carburetor before testing. A wet carburetor will hold the pressure better than a dry one.
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