Some customer comments have been received regarding no cold start capability or hot restart difficulty during mid-range engine temperature. Cases of no cold start may be the result of the glow plug inhibit switch not operating correctly. Reference Corporate Service Bulletin #866001 for glow plug system diagnosis.* Meanwhile, cases of poor hot/warm engine startup may be the result of starting system degradation, and may require glow plug assistance for engine starting. Replacement of the existing glow plug inhibit switch with a new service switch without a coolant temperature sensor (listed below) will provide glow plug assistance upon engine start, regardless of engine coolant temperatures. This feature will not reduce glow plug life.
1983-87 LH6*/LL4 - 23504005 1988-89 LL4 (Only) - 23504006 *1988-89 LH6 not equipped with glow plug inhibit switch
1. Disconnect batteries.
2. Replacement service switch can be installed in exact location of the inhibit switch with a socket wrench. (Do not use open end wrench.) Tighten to 19-27 Nm (13-20 lbs/ft). Replace any lost coolant.
3. Connect glow plug inhibit switch connector assembly to service switch.
4. Reconnect batteries.
Parts are currently available from GMSPO.
* Chevrolet Bulletin #88-49, GMC Truck Bulletin 88-T-39 and GM of Canada #88-662-100
Use applicable labor operation number and time.
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.