Engine - Smoke On Cold Start-Up

91chevy16

GMC NUMBER: 91-6A-86

GROUP: 6A Engine Mechanical

DATE: April, 1991

CORPORATE
NUMBER: 136101


SUBJECT: WHITE OR BLUE SMOKE ON COLD START-UP

MODELS: 1991 C/K R/V AND G TRUCKS AND VANS WITH 6.2L DIESEL ENGINES (VIN CODE C)


Condition: Following cold start-up, the engine misfires, runs rough and may produce objectionable blue or white smoke.

Cause: Some engines were timed too retarded and the housing pressure cold advance schedule controlled by the ECM was modified to a reduced time duration.

Correction: Engines timed with injection pump models DB-2829-4894 and 4895 below the injection pump serial number change point 6633950 and 6617332 respectively may be corrected by advancing (toward the driver side of the vehicle) the injection pump timing 1 mm or 2 degrees crankshaft rotation.


A new timing line should be stamped on the front cover to match the timing line on the injection pump flange. A letter "O" should then be stamped across the joint flange of both the engine timing cover and injection pump showing the correct timing by alignment of both halves of the letter "O". Correction of the housing pressure cold advance schedule will apply to all engines and requires replacement of the PROM's listed below:


6.2L DIESEL (RPO LH6) Broadcast
Model Emission Trans. Scanner I.D. Code Part Number
C/K Fed (NA5) 4 Speed Auto (MD8) 1415 AXMP 16161408
C/K Alt (NA6) 4 Speed Manual (M20) 1425 AXMR 16161410
5 Speed Manual (MT8)
R/V/G Fed (NA5) All 1425 AXMR 16161410
R/V/G Alt (NA6) All AXMS 16161412
C/K Fed (NA5) 4 Speed Manual (M20) 1445 AXMT 16161414
5 Speed Manual (MT8)

Parts are currently available from GMSPO.


NOTE: Some early built 1991 models did not have the correct starting label. The correct starting procedure to minimize white smoke is as follows:

SERVICE PROCEDURE:

1. Turn ignition key to the "run" position, then, depress the accelerator fully and release.

2. If glow plug/wait light is on, DO NOT crank the engine.


3. If glow plug/wait light does not come on, or when it goes off, turn ignition key to the "start" position and release the key when engine starts. If engine fails to start after 15 seconds cranking, return key to the "off" position. Wait one minute for the starter to cool, then repeat procedure.

WARRANTY INFORMATION

Use applicable labor number and times.