CAMPAIGN: FUEL INJECTION PUMP TIMING DIESEL AND MAN TRANS.. GMC Truck GMC K Pickup

SUBJECT: FUEL INJECTION PUMP TIMING

MODELS: 1991 C/K TRUCKS WITH 6.2L (LH6) DIESEL ENGINE & MANUAL TRANSMISSION

General Motors has determined that certain 1991 C/K trucks with 6.2L (LH6) diesel engines and manual transmissions may have the incorrect fuel injection pump timing and cold advance schedules. These trucks may experience cold running problems and fail to meet applicable emission requirements.

To correct this condition, dealers are to install a new calibration PROM in all involved trucks. Dealers are also to inspect and, if necessary, retime the fuel injection pump.

VEHICLES INVOLVED

Involved are certain 1991 C/K trucks with 6.2L diesel engines and manual transmissions built within the following VIN breakpoints:

Model Make Plant From Through ----- ---- ------ ----- --------- C/K GMC Oshawa SOP M1521745 Pontiac SOP ME5173341

The specific vehicles involved in this campaign have been identified by Vehicle Identification Number Computer Listings. These listings are furnished to all involved dealers with the campaign bulletin.

DEALER CAMPAIGN RESPONSIBILITY

All unsold new vehicles in dealers' possession and subject to this campaign MUST be held and inspected/repaired per the service procedure of this campaign bulletin BEFORE owners take possession of these vehicles.

Dealers are to service all vehicles subject to this campaign at no charge to owners, regardless of mileage, age of vehicle, or ownership, from this time forward.

Owners of vehicles recently sold from your new vehicle inventory are to be contacted by the dealer and arrangements made to make the required cor- rection according to instructions contained in this bulletin.

In summary, whenever a vehicle subject to this campaign enters your vehicle inventory, or is in your dealership for service in the future, please take the steps necessary to be sure the campaign correction has been made before selling or releasing the vehicle.

If the name and address of the owner of an involved vehicle was unavailable to GMC Truck Division at the time of campaign initiation, the dealer must determine the owner's name and address from the dealership sales records. Please provide this information directly on the second copy of the listing next to the applicable VIN so that our records may be updated and the appropriate notification mailed to the owner. This second copy should then be submitted to the address listed below in the previously supplied yellow campaign envelopes.

GMC Truck Division General Motors Corporation 101 Union Street Plymouth, Michigan 48170

OWNER NOTIFICATION

Owners will be notified of this campaign on their vehicles by GMC Truck Division (see copy of owner letter included with this bulletin). A listing of owner names and addresses has been furnished to the involved dealers to enable dealers to follow up with owners involved in this campaign. This listing may contain owner names and addresses obtained from State Motor Vehicle Registration records. The use of such motor vehicle registration data for any other purpose is a violation of law in several states. Accordingly, you are urged to limit the use of this listing to this campaign.

SERVICE PROCEDURE

INSPECTION INSTRUCTIONS

Inspect the fuel injection pump model number and serial number located on the fuel injection pump identification plate. The fuel injection pump must be retimed and the PROM replaced if either of the following is true:

-The model number is DB-2829-4894 and the serial number is less than 6633950, or

-The model number is DB-2829-4895 and the serial number is less than 6617332.

If neither of the above are true, only the PROM must be replaced.

PROM REPLACEMENT

(Required For All Vehicles)

1. Disconnect negative battery cable. 2. Remove glove box insert. 3. Remove ECM. 4. Remove ECM access cover. 5. Remove PROM from ECM. 6. Install new PROM and reinstall access cover. 7. Reinstall ECM. 8. Reinstall glove box insert. 9. Reconnect negative battery cable.

RETIMING PROCEDURE

(Required Only For Some Vehicles-See Inspection Procedure)

1. Advance (toward driver side of vehicle) fuel injection pump timing 1mm (equivalent to 2 degrees of crankshaft rotation).

2. Stamp a new timing line on front cover to match timing line on injection pump flange. Also, stamp a lefter "O" across the joint flange of both the engine timing cover and the injection pump to show the correct timing by alignment of both halves of the letter "O."

Notice: Page 6C2-8 of the 1991 C/K Truck Service Manual provides further details regarding this procedure.

--------------------------------------------------------------- | FOR ALL VEHICLES | | | | Install Campaign Identification Label when all campaign | | repairs are completed. | ---------------------------------------------------------------

PARTS INFORMATION

Parts are to be obtained from General Motors Service Parts Operation (GMSPO). To ensure that these parts will be obtained as soon as possible, they should be ordered from GMSPO on a C.I.O. order with no special instruction code but order under an advise code (2).

Part Number Description Quantity ----------- ---------------- -------- 16161414 Calibration PROM 1

WARRANTY INFORMATION

Dealers should submit a warranty claim on each vehicle completed under this campaign.

Labor Operation *Time Trouble Number Description Allowance Code --------- -------------- ---------- -------- V6890 Inspect/Retime 0.6 Hr. 96 Fuel Injection Pump and Install New PROM

V6891 Inspect injection 0.4 Hr. 96 Pump/install New PROM only

* For dealer to receive Administrative Time Allowance associated with this campaign, add 0.1 hour to the Labor Operation Time Allowance.

CAMPAIGN IDENTIFICATION LABEL

Each vehicle corrected in accordance with the instructions outlined in this Product Campaign Bulletin will require a "Campaign Identification Label." Each label provides a space to include the campaign number and five (5) digit dealer code of the dealer performing the campaign service. This information may be inserted with a typewriter or ball point pen.

Each "Campaign Identification Label" is to be located on the radiator core support in an area which will be visible when the vehicle is brought in for periodic servicing by the owner.

Apply "Campaign Identification Label" only on a clean, dry surface.

ADMINISTRATIVE PROCEDURE

Procedures covering this campaign are outlined in Section V of your dealership's "GM Truck Claims Procession Manual" #P9119.

Dear GMC Truck Owner:

To correct this condition, your dealer will install a new calibration PROM. Your dealer will also inspect and, if necessary, retime your fuel injection pump. This service will be completed for you at no charge.

Instructions for making this correction have been sent to your GMC Truck dealer. Please contact your dealer as soon as possible to arrange a service date. Please ask your dealer if you wish to know how much time will be needed to schedule, process and repair your vehicle.

Your GMC Truck dealer is best equipped to provide service to ensure your vehicle is corrected as promptly as possible. However, if you take your vehicle to your dealer on the agreed service date and they do not service this condition on that date or within five days, we recommend you contact your nearest GMC Truck Zone Office by telephone. The Zone Office will assist you and your dealer in getting your vehicle corrected. The telephone numbers of the Zone Offices are listed in your Warranty and Owner Assistance Information Manual.

After contacting your GMC Truck dealer and the Zone Office, if you are still not satisfied that we have done our best to remedy this condition without charge within a reasonable time, you may wish to write the Environmental Protection Division (EN-340F), United States Environmental Protection Agency, 401 M Street, S.W., Washington, D.C. 20460. To ensure your full protection under the emission warranty made applicable to your vehicle by Federal Law, and your right to participate in future recalls, it is recommended that you have your vehicle serviced as soon as possible. Failure to do so could legally be determined to be lack of proper maintenance of your vehicle. Also, your vehicle may fail a state or local emission inspection test if the recall work is not accomplished.

Should your dealer find that your emission system has been intentionally disabled, you will be asked if you wish the system to be restored so that it will function as designed. The cost of such restoration will be your responsibility.

The enclosed postage paid owner reply card identifies your vehicle. Presentation of this card to your GMC Truck dealer will assist in making the necessary correction to your vehicle in the shortest possible time. If you have sold or traded your vehicle, please furnish us complete name and address of the person you sold or traded your vehicle to and retum the card to us.

We are sorry to cause you this inconvenience; however, we have taken this action in the interest of your continued satisfaction.

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.