Testing Check Valve

The fuel pump check valve holds residual fuel pressure in the fuel lines after the engine is turned off. This residual pressure aids in quick starting and helps prevent fuel line vapor lock. The fuel pump check valve is part of the pump assembly and not separately replaceable.




TESTING FUEL PUMP CHECK VALVE
1. Connect the fuel pressure gauge as shown.

WARNING: Fuel will be expelled under pressure when fuel lines are connected and disconnected. Do not smoke or work near heaters or other fire hazards. Keep a fire extinguisher handy.

2. Close the pressure gauge shutoff valve. Run the fuel pump in short intervals until the fuel pressure reaches the initial test pressure of 3.0 bar (44 psi). Turn the fuel pump off.

NOTE: Pressure will build quickly. Operate the pump in short intervals only. If necessary, open the shutoff valve slowly to bleed off excess pressure.

3. After ten minutes, the gauge reading should indicate 2.0 bar (29 psi).

4. If the pressure drops too quickly, check for leaks in the fuel lines or fuel injectors. If no leaks are found, the most likely cause is the fuel pump check valve. To further isolate the problem. repeat the above test and then quickly pinch off the return line to the fuel tank. If the pressure now holds steady, the fault is in the pump check valve. If the pressure still drops off, check for faulty fuel injection components.

NOTE: An in-line check valve is used in the return line near the pump outlet.