Glow Plugs
- Battery voltage must be higher than 11.5 volts. Connect test light between No. 4 cylinder glow plug and ground. Turn ignition to "ON" position for no more than 15 seconds. Test light should come on. If not, check glow plug relay, ignition switch, or fuse box relay plate.
- If test light glows, turn ignition "OFF". Connect ammeter between No. 4 cylinder glow plug and battery positive lead. Turn ignition switch "ON" for several seconds. Initial current draw can be as high as 140 amps but should stabilize at 36 amps within seconds.
- Total current draw of less than 36 amps indicates one or more defective glow plugs. Current draw of 27 amps indicates 1 bad glow plug, 18 amps indicates 2 bad glow plugs, and 9 amps indicates 3 bad glow plugs.
- If total current draw exceeded 36 amps in step 2), check current to each individual glow plug. Replace any glow plug drawing more than 9 amps. To determine inoperative glow plug, disconnect wiring and bus bar from plugs. Connect test light to positive battery terminal.
- Touch test light probe to each glow plug in turn. If light glows, glow plug is good. If light does not glow, glow plug is defective and should be replaced. If glow plugs check OK but engine is hard to start, remove glow plugs and clean any carbon off heating element. Reinstall plugs and check engine starting.