CAMPAIGN:DIESEL FUEL FILTER SENSOR-NEG.VOLT. TRANSIENTS

MODELS: 1984 CK 15-35 Model Light Duty Trucks With LH6/LL4 6.2L Diesel Engine

General Motors has determined that some 1984 Light Duty Model Trucks equipped with 6.2L Diesel Engines (RPO LH6 and LL4) may have a condition which can cause grounding of the Stanadyne fuel filter water-in-fuel (WIF) sensor.

This grounding can damage the WIF sensor module and other electrical components. The condition is caused by negative voltage transients, during engine shut off, damaging an unprotected semiconductor in the WIF sensor module.

An inoperative WIF sensor can allow excessive amomts of water in the fuel to go undetected resulting in extensive damage to the fuel injection pump.

To prevent the possibility of this condition occurring, it will be necessary to replace the WIF sensor harness assembly.

VEHICLES INVOLVED

Involved are certain 1984 Light Duty Model Trucks equipped with 6.2L Diesel Engines (RPO LH6 and LL4). The following is a list of the vehicles involved:

Zone Dealer VIN ---- ------ --- 58 58317 2GTEC14C6E1500554

36 36199 2GTGC24J6E1500261 36262 2GTGC24JSE1500509 36138 2GTDC14C2E1500546 36372 2GTEK24C6E1500580 3616S 2GTDC14CXE1500620 36115 2GTEC14C7E1503205

21 21546 2GTGK24J1E1500672

14 14016 2GTEC14C7E1500370 14629 2GTDC14CSE1503103

10 10387 2GTEC14C8E1500586 10092 2GTEK14C4E1500474 10593 2GTGC24J1E1500362 10068 2GTEC14C1E1500431

06 06113 2GTFC24C8E1500484

02 02210 2GTEC14C3E1500415 02382 2GTEC14C7E1500420 02320 2GTEK14C6E1500301 02S07 2GTGK24JXE1503196

The specific vehicles involved in this campaign have been identified by Vehicle Identification Number Listings contained in this bulletin.

Since all vehicles are still in dealer stock, no owners are involved and therefore no owner letter is attached.

SERVICE PROCEDURE

1. Disconnect negative battery cables.

2. Locate fuel filter assembly on front of cowl. (See Figure 1) WIF Sensor is located at bottom rear of filter and has a four wire harness to it.

3. Disconnect fuel heater harness connection at top of filter. (See Figure 2)

4. Remove three screws (3/8 X 16 X 1 1/8) attaching filter to cowl while supporting filter.

5. Move filter away from cowl and hold so that rear of filter is facing up.

6. Disconnect engine wiring harness to WIF sensor harness connection and disconnect WIF sensor harness from filter body.

7. Unsnap filter canister (loosen 2 clips) but do not remove canister.

8. Remove two screws (8 X 32) holding WIF sensor.

9. Remove WIF sensor and install revised WIF sensor with diode in wiring harness.

10. Assemble and tighten two WIF sensor retaining screws to 113-170 N-cm (10-15 lb-in)

11. Reassemble canister retaining clips.

12. Reconnect WIF sensor harness to filter body and to engine wiring harness.

13. Raise filter assembly back to cowl, replace three attaching screws and tighten to 27-40 N-m (20-29 lb-ft).

14. Connect fuel heater harness to engine harness.

15. Reconnect battery cables.

16. Start engine and check for fuel leaks.

PARTS INFORMATION

Parts required to complete this campaign will be shipped to involved dealers by GMC Truck on a no charge basis. Any questions as it pertains to parts shortages, etc., should be directed to your Zone Service Department.

Part Name Part Number Quantity Per Vehicle Parts Allowance --------- ----------- -------------------- --------------- Water Sensor NPN 1 $1.80

The $1.80 identified in the "Parts Allowance Column" represents 30% of dealer net when parts are furnished at no charge by GMC Truck. This amount is to be placed in the Net Item Amount column of the claim and use type code 'M'.

WARRANTY INFORMATION

Dealers should submit an accurately filled out Warranty Repair Order on each vehicle completed under this campaign.

Labor *Time Trouble Operation Number Description Allowance Code ---------------- ----------- --------- ---- V1810 Replace WIF Sensor 0.5 HR 96

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

CAMPAIGN IDENTIFICATION LABEL

Each vehicle modified 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 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 "GMC Truck Claims Processing Manual" issued October, 1981.

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.