Glow plugs are essential components in starting a diesel motor. The GM 6.2 L diesel was installed in GM and Chevy trucks between 1982 and 1993 and it had two different electronic controllers during this production period. You must determine which type of controller your ignition system uses, then troubleshoot the ignition system. Glow plugs come on before, during and briefly after engine ignition. How long they stay on depends largely on the temperature of the engine coolant, and they stay on longer in cold weather than in warm weather. A burned-out plug usually indicates problems elsewhere in the ignition system.
To check operation of the glow plug system, put the ignition switch in the run position (but don't crank it) and see if the glow plug light on the dash lights up for eight to 10 seconds and goes out.
Start the engine. The glow plug light should come on briefly after ignition and possibly cycle on several times. If it does not come on or simply stays on, your ignition controller likely needs repair.
Check all the glow plugs with the ammeter. If a glow plug heats up when electrified, it is working properly. If it does not heat up or does not stay heated, replace it.
Check that all your fuses and ground wires are intact, clean and properly tightened.
Get behind the wheel and watch the glow plug light on the dashboard to see if it is cycling properly. If the glow plug light only comes on once after ignition, the problem is likely the controller. Replace the controller.
Replace any glow plugs you determine to be faulty by disconnecting the glow plug wire, then lowering a socket on a socket extender down into the glow plug well. Use your fingers to turn the extender until the socket fits snugly over the glow plug. Attach the socket handle, then loosen and remove the glow plug. Insert the replacement plug in the socket and reverse the procedure, finishing by reconnecting the glow plug wire.
