8A - Electric Fuel Pump Inlet Restriction

8a. Electric Fuel Pump Inlet Restriction





Purpose:
To determine if there is excessive restriction of fuel flow between the fuel tank and the inlet line to the electric fuel pump.





Fuel is drawn from the fuel tank through the primary filter (the screen on the fuel tank sending unit) by the electric fuel pump. Pressurized fuel (approximately 30-80 psi) is supplied to the secondary filter (the fuel filter housing is located in the V on top of engine) by means of electric pump and regulator valve. The regulator relieves the pressure, sending fuel back to the fuel tank. Only the filtered fuel going through fuel filter will go to the heads. A check valve is located on both heads to prevent fuel pressure spikes in fuel rail.





Recommended Procedure:
First verify that there is fuel in the tank and battery voltage going to the fuel pump, using a digital multimeter connected between the two circuits going to the pump. Battery voltage will be present for approximately 20 seconds when the ignition key is turned ON. If no voltage is present, go to Pinpoint Test FK. FK - Fuel Pump Monitor/Control

Remove the fuel line to the inlet side of the fuel pump. Install Rotunda Low Fuel Pump Adapter 014-00931-2 or equivalent between the fuel inlet line and the electric fuel pump. Connect test adapter to gauge (0-30 in-Hg vacuum). Measure restriction at wide open throttle (maximum engine speed out of gear with the brakes set and the wheels blocked). If restriction measures above specification (6 in-Hg), there is a blockage between the fuel pump and the fuel tank.

Possible Causes:
- A plugged, kinked or severely bent fuel supply line.
- plugged fuel sending unit screen