DIESEL ENGINE INFO. UPDATE 350 CU. IN. (5.7L)

THIS BULLETIN CONTAINS MULTIPLE SUBJECTS. PAGE THROUGH TO DESIRED SUBJECT.

DIESEL OIL PUMP DRIVE SHAFT

WHEN AN OIL PUMP DRIVE SHAFT CONDITION IS ENCOUNTERED WHERE THE HEX IS ROUNDED OFF INSIDE THE VACUUM PUMP DRIVE GEAR, THE OIL PUMP DRIVE EXTENSION SHAFT, P/N 559127, AND THE VACUUM PUMP DRIVE UNIT, P/N 7832145, SHOULD BE REPLACED.

OCCASIONALLY DIFFICULTY IN THE REMOVAL OF THE VACUUM PUMP IS ENCOUNTERED AS THE OIL PUMP DRIVE SHAFT ROUNDS OUT IN THE VACUUM PUMP. TO EASE REMOVAL WHEN THIS IS ENCOUNTERED, ROTATE THE ENGINE BACKWARDS APPROXIMATELY 1/4 TURN AND THEN REMOVE VACUUM PUMP.

IF OIL PUMP DRIVE SHAFT AND GEAR ASSEMBLY ARE TO BE REPLACED, USE P/N 22511730 FOR ALL DIESEL MODELS.

DIESEL ROUGH IDLE GLOW PLUG RESISTANCE PROCEDURE

A NOZZLE WITH A TIP LEAK CAN ALLOW MORE FUEL THAN NORMAL INTO THE CYLINDER WHICH WILL RAISE THE GLOW PLUG OHM READING. THIS WILL ROB FUEL FROM THE NEXT NOZZLE IN THE FIRING SEQUENCE AND WILL RESULT IN THAT GLOW PLUG HAVING A LOW OHM READING. IF THIS IS ENCOUNTERED IT IS ADVISABLE TO REMOVE, AND CHECK THE NOZZLE WITH A HIGH READING, IF IT IS LEAKING IT COULD BE CAUSING THE ROUGH IDLE.

SOME GLOW PLUGS HAVE BEEN FOUND TO INCREASE IN RESISTANCE WITH HEAT. IF YOU EXPERIENCE LOW READINGS ON A GLOW PLUG AND IT DOES NOT CHANGE WITH NOZZLE CHANGE, SWITCH GLOW PLUGS BETWEEN A GOOD AND BAD CYLINDER. IF THE READING OF EACH CYLINDER IS NOT THE SAME AS BEFORE THE SWITCH, THE GLOW PLUG CAN NOT BE USED FOR ROUGH IDLE DIAGNOSIS ALTHOUGH IT WILL FUNCTION FOR STARTING THE CAR.

DIESEL INJECTION NOZZLE BODY LEAKS

NOZZLE BODY LEAKS MAY BE CORRECTED BY LOOSENING THE INLET FITTING AND RE- TORQUING (DED 45 FT. LBS. - CAV 19 FT. LBS.) IN THE EVENT THIS DOES NOT CORRECT THE LEAK, POLISHING THE INLET FITTING MAY CORRECT THE LEAK. REMOVE THE INLET FITTING, LAY A PIECE OF 600 GRIT SAND PAPER OR CROCUS CLOTH ON A HARD FLAT SURFACE. PRESS AND ROTATE THE END OF THE INLET FITTING AGAINST THE PAPER, ROTATE BACK AND FORTH ABOUT SIX (6) TIMES. FLUSH WITH DIESEL FUEL AND REASSEMBLE.

DIESEL - BASIC SERVICE ENGINE

FUTURE 1980 MODEL DIESEL BASIC SERVICE ENGINES WILL HAVE 1981 FEATURES IN- CORPORATED THAT IS 1981 CRANKSHAFTS, ROD BEARINGS AND MAIN BEARING CAP BOLTS. 1981 SERVICE PROCEDURES MUST BE OBSERVED WHEN SERVICING THESE COMPONENTS. THESE ENGINES CAN BE IDENTIFIED BY NOTING THE DISPLACEMENT CASTING CODE ON THE SIDE OF THE BLOCK. ALL DIESEL ENGINE BLOCKS WITH 1981 FEATURES WILL BE MARKED 350DX.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.