Fuel Pump Functional Tests

NOTE: Prior to performing fuel pump tests inspect all hoses and lines, for kinks and bends that may cause restrictions. The following test will check fuel pump pressure, volume, and vacuum.
1. Remove the air cleaner assembly and disconnect the fuel inlet fitting at the carburetor.
2. Disconnect the fuel return hose at the fuel filter and plug the nipple on the filter.
3. Connect a pressure gauge 0-104 kPa (0-15 psi) range, to the fuel line.
4. Using the starter motor, crank the engine several times while observing the pressure gauge. The pump should develop 40-50 kPa (5.75-7.25 psi). If the fuel pump does not develop the listed pressure and the fuel filter is in good condition, the pump is defective and must be replaced.
5. Disconnect the pressure gauge.
6. Connect a sufficient length of hose to the fuel line and using an approved container, START the engine and let the fuel from the fuel pump run into the container. The fuel pump should supply .95 L (1 qt) of fuel in one minute or less at idle. If the pump fails to supply the listed volume and the fuel filter is in good condition the fuel pump must be replaced.
7. Reconnect the fuel lines at the carburetor and fuel filter, START the engine and check for leaks.
8. Disconnect the inlet and outlet fuel lines from the fuel pump. Wrap a suitable shop towel around fittings to catch any fuel spills.
9. Connect a vacuum gauge 0-85 kPa (0-25 in-hg) minimum range, to the fuel pump inlet fitting. Using the starter motor, turn the engine over several times and observe the vacuum gauge. The pump should develop a minimum of 37.4 kPa (11 in-hg) of vacuum, and may read as high as 74.8 kPa (22 in-hg). If the pump does not develop the minimum listed vacuum it is defective and must be replaced.
10. Remove the vacuum gauge, reconnect the fuel fittings, reinstall the air cleaner assembly, START the engine and test for leaks.