Engine - Hard Starting/Poor Performance

9227ford01

Article No.
92-10-9

May 6, 1992


^ FUEL SYSTEM - 7.3L DIESEL ENGINE - DIAGNOSTIC PROCEDURE FOR DETECTING AIR LEAKS

^ HARD START - 7.3L DIESEL ENGINE - FUEL SYSTEM AIR LEAKS

^ POOR PERFORMANCE OR LACK OF POWER - 7.3L DIESEL ENGINE - FUEL SYSTEM AIR LEAKS


LIGHT TRUCK: 1988-92 E-250, E-350, F SUPER DUTY, F-250, F-350


ISSUE:
Hard starting and poor engine performance may be caused by air leaks in the diesel fuel system supply lines. Hard start concerns may also be caused by air leaks in diesel fuel system return lines. In some cases, air leaks have resulted in unnecessary fuel injection pump replacement.

ACTION:
If service is required, use the following diagnostic procedure and a Rotunda One Hand Vacuum Pump 021-00037 or equivalent to detect air leaks in the diesel fuel system.


NOTE:
A LIQUID TRAP MAY BE ATTACHED TO THE VACUUM PUMP TO CONDUCT THESE TESTS. PRIOR TO USE, CONFIRM THE INTEGRITY OF THE TRAP.





ENGINE MOUNTED FUEL SYSTEM PROCEDURE

Check the engine mounted fuel system using the following procedure, Figure 1.

1. Disconnect the fuel supply line at the fuel supply pump.

2. Plug the fuel supply pump inlet.

3. Disconnect the fuel return line from the fitting located at the left rear corner of the engine.

4. Attach the hand operated vacuum pump to the fitting at the fuel return line attachment point.

5. Apply a vacuum of 10 inches Hg.

6. If the vacuum decay exceeds 1/2 inch Hg. in 15 minutes, an air leak is present.


7. If an air leak is not present, follow the Vehicle Fuel System Procedure in this article to check the remainder of the fuel system.

8. If an air leak is present, test the engine mounted fuel system one component or connection at a time until the leak is eliminated.

9. After the air leak has been eliminated, follow the Vehicle Fuel System Procedure in this article to check the remainder of the system.

VEHICLE FUEL SYSTEM PROCEDURE

After completing the Engine Mounted Fuel System Procedure in this article, use the following procedure to check the remainder of the vehicle fuel system.

1. Disconnect the fuel supply line from the fuel tank sending unit.

2. Plug the end of the supply line.

3. Disconnect the fuel return line from the fuel tank sending unit.

4. Attach the hand operated vacuum pump to the end of the return line.

5. Apply a vacuum of 10 inches Hg.

6. If the vacuum decay exceeds 1/2 inch Hg. in 15 minutes, an air leak is present.

7. If an air leak is present, test the remainder of the fuel system one component or connection at a time until the leak is eliminated.

8. If an air leak is not present, check other systems for the cause of the concern.


WARRANTY STATUS:
Eligible Under Bumper To Bumper For 1992 Models And Basic Warranty Coverage For 1991 And Prior Models
OPERATION DESCRIPTION TIME
921009A Equipment Hook Up And 0.6 Hr.
Diagnostic Steps - F-Series
921009B Equipment Hook Up And 0.7 Hr.
Diagnostic Steps - Econoline
DEALER CODING
BASIC PART NO. CONDITION CODE
9K159 33
OASIS CODES: 404000, 602300, 614000, 614500, 614600