Diesel Engine Troubleshooting

Ford 7.3L DI Air in Lube Oil

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Aeration often results in hard or no-starts, erratic idle, shutdowns on deceleration, and loss of rpm. CG4/SH oil helps control the problem. As originally specified, 1994-model engines held 12 quarts of crankcase oil. This specification has been revised to 14 quarts. The dipstick should be recalibrated or replaced with Ford PN F4TZ-6750-E.

Leaks at pump pickup tube o-ring can be detected by jacking the rear wheels 10 in. off the ground and overfilling the crankcase with three quarts of oil. If the idle smoothes out, replace the o-ring seal.

In addition to its effect on performance, air in the oiling system causes rapid injector wear. Whenever an injector is changed, the associated cylinder bank should be purged:

• Disconnect the CMP to prevent the engine from starting.
• Mechanical fuel pumps (pre-1998 models)—disconnect the return line at the fuel pressure regulator on the fuel filter. Crank the engine in 15-second bursts, allowing ample time for the starter to cool and until a steady stream comes out of the line.
• Electric fuel pumps—crack a vent port on each cylinder head and run the pump until air is purged.

If head galleries have been drained, prefill the galleries with pressurized oil as described under “Low oil pressure.”

Written by Ed

February 14th, 2011 at 7:58 am

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