Fuel Pump: Testing and Inspection

Toyota Diagphragm Fuel Pump

This test was published in 1989 and applies to the Toyota 22r engine, other carbureted engines using diagphragm type fuel pumps are similar but test data may not be available.

SYSTEM TEST:

1. Using a Tee fitting and fuel hose, connect a low pressure fuel pressure gauge in-line between the fuel pump outlet and the carburetor inlet.
2. Start the engine and observe the gauge readings.

Fuel Pressure: 2.8 - 4.3 PSI

3. If fuel pressure is zero, ensure that the fuel tank has fuel. Also check fuel filter for blockage or restriction.
4. Raise engine rpm to 3,000 rpm and check gauge reading. If a drop in fuel pressure occurs, remove the fuel pump for component testing. See COMPONENT REPLACEMENT AND REPAIR PROCEDURES.
5. If no problems are found, remove the fuel pressure gauge from the engine.
6. Reconnect all fuel hoses.
7. Start engine and check for fuel leaks.

COMPONENT TESTS:

1. With the fuel pump removed from the engine, operate the pump lever by hand and check for excessive arm play tension.
2. Block off the outlet and return pipes with your fingers and check that there is an increase in lever arm play. Ensure that the lever arm moves freely indicating that air is trapped in the pump.

Checking The Fuel Pump Inlet Valve:

3. Block off the inlet pipe with your finger and check that the pump arm is now locked (cannot be depressed easily). DO NOT force the arm to depress.

Checking The Fuel Pump Outlet Valve:

4. Check the pump diaphragm by blocking off all three of the pipes with your fingers and attempting to depress the pump arm. It should lock as in step 3.

Checking The Fuel Pump Diaphragm:

5. If any deficiencies are found, replace the fuel pump.
6. Block off the vent holes under the pump casting with your fingers. Check that the pump arm locks.

Checking The Fuel Pump Oil Seal:

7. If the arm does not lock, the oil seal is bad and the fuel pump should be replaced.