ADDITIONAL MISC. DIESEL INFO. MULTIPLE SUBJECTS

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

DIESEL FUEL RESERVE

THE 1981 MODEL DIESEL FUEL GAGES WERE REDESIGNED FOR MORE ACCURACY, DUE TO A CHANGE IN THE FUEL RESERVE. RESERVE CAPACITY HAS BEEN REDUCED TO APPROXI- MATELY 1/2 TO 3 GALLONS, WHICH IS STATED IN THE 1981 OWNERS MANUAL AS "LESS THAN FIVE GALLONS".

ALL 1981 MODEL DIESEL CARS HAVE A CHECK VALVE IN THE FUEL TANK FILTER WHICH WILL PERMIT FUEL TO PASS SHOULD THE TANK FILTER BECOME PLUGGED WITH PARAFFIN WAX DURING COLD WEATHER OPERATION. IF THIS HAPPENS THE LAST FOUR GALLONS OF FUEL WILL NOT BE REMOVED FROM THE TANK DUE TO THE LOCATION OF THE CHECK VALVE CUSTOMERS SHOULD BE ADVISED TO KEEP THEIR TANKS ABOVE THE 1/4 MARK AT TEMPERA- TURE BELOW 20 DEGREES TO PREVENT RUNNING OUT OF FUEL.

DIESEL INJECTION LINE

1981 MODEL DIESEL INJECTION LINES WILL NOT FIT THE 1980 DIESEL. ALTHOUGH THE LINE FITTINGS INTERCHANGE, THEIR CONFIGURATION AND VOLUME DIFFER.

981 DIESEL PARTIAL BLOCKS MISPACKAGED AS 1980

SOME 1981 MODEL DIESEL ENGINE PARTIAL BLOCKS HAVE BEEN MISPACKAGED BY GMPD AS 1980 MODEL DIESEL ENGINE BLOCKS. THE MISPACKED 1981 MODEL ENGINE PARTIAL BLOCKS ARE NOT TO BE USED IN 1980 MODELS. SIZE OF LIFTER BORES ARE THE MAJOR DIFFERENCE. THE 1980 MODEL DIESEL ENGINE PARTIAL BLOCKS WITH CRATE CODE GKO-X ARE CORRECTLY PACKAGED.

DIESEL ENGINE NOISE

A LIFTER TYPE NOISE IN DIESEL ENGINES THAT IS THROTTLE CONSCIOUS AND MOST NOTICEABLE WHEN THE ENGINE IS WARM COULD BE CAUSED BY A WORN WRIST PIN BUSHING IN THE CONNECTING ROD.

1981 DIESEL - WHITE SMOKE COLD ENGINE START

WHITE SMOKE AT START UP AFTER SETTING OVERNIGHT IS THE RESULT OF OPENIG THE EXHAUST VALVES BEFORE THE FUEL HAS COMPLETELY BURNED. THE HOUSING PRESSURE COLD ADVANCE (HPCA) FEATURE OF THE THE INJECTION PUMP IS DESIGNED TO ADVANCE THE TIMING BY 3 DEG. DURING WARM UP TO PREVENT THIS CONDITION. THE HPCA SOLENOID LOCATED INSIDE THE FUEL INJECTION PUMP COVER IS ACTIVATED BY CURRENT FLOW THROUGH THE COOLANT SWITCH WHEN ENGINE TEMPERATURE IS LESS THAN 120 DEG. F. CHECK FOR CURRENT AT THE HPCA TERMINAL LOCATED ON THE SIDE OF THE INJEC- TION PUMP COVER AT COOLANT TEMPERATURES BELOW 120 DEG. F. REPAIR CAUSE OF A NO CURRENT CONDITION. IF CURRENT IS AVAILABLE AT HPCA TERMINAL REMOVE INJECTION PUMP COVER, THE SOLENOID INSIDE COVER SHOULD ACTIVATE. IF THE SOLENOID DOES NOT ACTIVATE, THE COVER ASSEMBLY SHOULD BE SENT TO A ROOSA MASTER REPAIR STATION FOR CORRECTION.

DIESEL FUEL LINE HEATER

OPERATION OF THE FUEL LINE HEATER CAN ONLY BE CHECKED COLD (BELOW 20 DEG. F). AFTER SEVERAL MINUTES OF OPERATION, THE OUTLET PIPE WILL BE WARMER TO THE TOUCH THAN THE INLET. IT CAN ALSO BE CHECKED WITH AN OHMMETER BY MEASURING RESISTANCE TO GROUND WHEN THE THERMOSTATIC SWITCH IS CLOSED (BELOW 20 DEG. F). SHOULD BE LOW (LESS THAN 5 OHMS) INDICATING CONTINUITY.

THE HEATER ELECTRICAL SYSTEM IS PROTECTED BY A FUSIBLE LINK WHICH IS THE ORANGE WIRE COMING FROM THE UNIT.

DIESEL ENGINE OIL VISCOSITY

THE ENGINE OIL VISCOSITIES RECOMMENDED FOR DIESEL ENGINES ARE SAE 30 AND SAE 10W30. 10W40 AND OTHER MULTI-GRADE OILS ARE NOT RECOMMENDED. THE USE OF OIL WITH INCORRECT VISCOSITY CAN CAUSE ENGINE PROBLEMS. ENGINE COMPONENT FAILURE OF ANY NATURE WHICH ARE DUE TO INCORRECT OIL VISCOSITY ARE NOT CONSIDERED A MANUFACTURING DEFECT.

1981 DIESEL - ALL SERIES - BLACK SMOKE AND LOW POWER

WHEN INVESTIGATING A CONDITION OF BLACK SMOKE AND LOW POWER, CHECK FOR THE PROPER OPERATION OF THE EXHAUST PRESSURE REGULATOR (EPR) VALVE. THE VALVE IS CLOSED AT IDLE TO INCREASE EXHAUST PRESSURE WHICH INCREASES EGR FLOW TO THE ENGINE. THE EPR VALVE PENS ABOVE IDLE TO ACHIEVE A NORMAL EGR LEVEL FOR TYPICAL DRIVING.

"CHUGGLE" AT LIGHT THROTTLE, 40 MPH OR ABOVE

A CHUGGLE CONDITION UNDER LIGHT LOAD WITH THE CONVERTER CLUTCH LOCKED UP MAY BE CORRECTED BY THE FOLLOWING STEPS:

- CHECK PUMP TIMING. IT SHOULD BE EXACTLY ON THE MARK. IF RETARDED, IT COULD CAUSE A CHUGGLE CONDITION.

- CHECK FOR A PLUGGED FUEL INLET; THERE SHOULD BE GOOD PRESSURE COMING OUT OF THE FUEL FILTER. TO CHECK, LOOSEN THE FITTING AND THE FUEL SHOULD SPRAY FROM THE FITTING.

- VERIFY THAT PUMP HOUSING PRESSURE IS WITHIN SPECIFICATIONS.

- NOZZLE WILL NORMALLY CONTRIBUTE TO A ROUGH IDLE, THEREFORE A ROUGH IDLE CONDITION SHOULD BE CORRECTED BEFORE TRYING TO CORRECT CHUGGLE.

- ON CARS WITH THE CONVERTER CLUTCH THE INJECTION PUMP MUST HAVE A VENTED ROTOR. CHECK TO BE CERTAIN CORRECT PUMP HAS BEEN INSTALLED. REFER TO PARTS CATALOG FOR USAGE.

DIESEL TRANSFER PUMP COVER

WE HAVE RECEIVED REPORTS CONCERNING DAMAGE TO THE TRANSFER PUMP COVER ON THE INJECTION PUMP. WHEN REMOVING THE INJECTION LINES, IT IS IMPORTANT THAT YOU DO NOT DAMAGE THE TRANSFER PUMP COVER (BLACK IN COLOR), WITH THE WRENCH. IF THE COVER IS DAMAGED (A DIMPLE OR CRACK), IT COULD CAUSE THE INJECTION PUMP TO ALLOW AIR TO ENTER THE SYSTEM CAUSING ROUGH IDLE.

1980-81 DIESEL - BASIC SERVICE ENGINES - DOWEL PIN DELETION

WHEN ORDERING A 1980-81 DIESEL BASIC SERVICE ENGINE FROM GENERAL MOTORS WAREHOUSING AND DISTRIBUTION DIVISION (GMWDD) IT WILL NO LONGER CONTAIN DOWEL PINS ON THE CYLINDER BLOCK SURFACE TO LOCATE CYLINDER HEADS AND GASKETS. THIS IS BEING DONE TO REDUCE BASIC ENGINE PART NUMBERS STOCKED BY GMWDD. WHEN ORDERING A BASIC ENGINE, DEALERS WILL NEED TO ORDER QUANTITY 1 OF PART NUMBER 585927 (DOWEL PIN), THIS IS A BOX OF 20 PIECES WHICH IS ENOUGH TO DO FIVE ENGINES. THEY SHOULD BE INSTALLED IN THE NEW BLOCK IN THE SAME LOCATION AS IN THE ENGINE BEING REPLACED. HOLES WILL BE PROVIDED IN THE SERVICE BLOCKS AT THE NECESSARY DOWEL PIN LOCATION POINTS. A NOTE WILL BE FORTHCOMING IN THE GMWDD PARTS BOOKS TO THIS EFFECT.

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.