Fuel Return System Diagnosis

Fuel Return System Diagnosis

FROM THE ENGINE TO THE TANK
1. Disconnect the return line at the engine, metal collar.
2. Remove the fuel filler cap.
3. Apply 1 psi air at the fuel return line that leads back to the tank.
4. Listen at filler tube for air.
5. If air is present, return line is okay. If air is not present, disconnect the return line at the sender assembly.
6. Retest using 1 psi at the fuel return line back to the tank.
- If air is present, the return line is okay. Check and replace the sender assembly.
- If air is not present, repair the restriction in the return line.

FROM THE ENGINE TO THE INJECTOR SPILL LINES




1. Disconnect the fuel return line (1) at the engine.
2. Remove the air duct from the air cleaner assembly to the turbo inlet.
3. Remove the air intake pipe.




4. Remove the fuel return rubber hose of the fuel injection pump from the junction block (2). Cap the fitting on the block with a 3/8 inch rubber cap (1) to prevent fuel leakage.
5. Install the J 23738-A Vacuum Pump at the fuel return pipe.
6. Apply 15 inches Hg of vacuum to the pipe.
- If the vacuum holds, go to step 13.
- If the vacuum does not hold, go to step 7.
7. Remove the generator.




8. Remove the fuel return line (1) connecting the right front and left rear cylinder heads.




9. Install the J 23738-A onto the right front cylinder head return port (1).
10. Apply 15 inches Hg of vacuum to the port.
- If the vacuum holds, go to step 11.
- If the vacuum does not hold, the leak is in the spill lines under the valve cover. Install the fuel return line between the cylinder heads, remove the lower right valve cover, and go to step 15 of Fuel Leaks (inside of Engine).
11. Install the J 23738-A onto the left rear cylinder head return port.
12. Apply 15 inches Hg of vacuum to the port.
- If the vacuum holds, replace the leaking fuel return line between the cylinder heads.
- If the vacuum does not hold, the leak is in the spill lines under the valve cover. Install the fuel return line between the cylinder heads, remove the lower right valve cover, and go to step 15 of Fuel Leaks (inside of Engine).




13. Remove the cap (1) from the junction block (2).
14. Reinstall the fuel injection pump fuel return hose on the junction block and clamp the hose.
15. Install the air duct on the air cleaner assembly to the turbo inlet.
16. Install the air intake pipe.
17. Reinstall the fuel return line to the engine.
18. Install the generator.
19. Start and idle the engine, and check for leaks.