Fuel Return System Diagnosis EFI/MFI

Any restriction in the fuel return system could greatly effect the driveability of the vehicle. If other diagnosis indicates or if the fuel return system is suspected of being restricted, the fuel return system should be tested.

1. Disconnect the hose of the fuel return line at the fuel sender.
2. Disconnect the hose of the fuel return line at the injection pump.
3. Connect a vacuum pump with a gauge to the hose.
4. Apply vacuum to the return line.
5. Observe the gage reading.

•	If the vacuum does not build and hold, Go to Step 4.

•	If the vacuum builds and holds, repair the return line restriction.

6. Connect the fuel return line at the injection pump and the fuel sender.
7. Clean any fuel spillage.
8. Run the engine to check for fuel leakage.