DIESEL ROUGH IDLE GLOW PLUG RESISTANCE PROCEDURE

A NOZZLE WITH A TIP LEAK CAN ALLOW MORE FUEL THAN NORMAL INTO THE CYLINDER WHICH WILL RAISE THE GLOW PLUG OHM READING. THIS WILL ROB FUEL FROM THE NEXT NOZZLE IN THE FIRING SEQUENCE AND WILL RESULT IN THAT GLOW PLUG HAVING A LOW OHM READING. IF THIS IS ENCOUNTERED IT IS ADVISEABLE TO REMOVE, AND CHECK THE NOZZLE WITH A HIGH READING, IF IT IS LEAKING IT COULD BE CAUSING THE ROUGH IDLE. SOME GLOW PLUGS HAVE BEEN FOUND WHICH DO NOT INCREASE IN RESISTANCE WITH HEAT. IF YOU EXPERIENCE LOW READINGS ON A GLOW PLUG AND IT DOES NOT CHANGE WITH NOZZLE CHANGE, THEN SWITCH GLOW PLUGS BETWEEN A GOOD AND BAD CYLINDER. IF THE READING OF EACH CYLINDER IS NOT THE SAME AS BEFORE THE SWITCH, THEN THE GLOW PLUG CAN NOT BE USED FOR ROUGH IDLE DIAGNOSIS ALTHOUGH IT WILL FUNCTION FOR STARTING THE CAR.

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.