DIAGNOSIS & TESTING
- Disconnect the engine temperature sensor.
- Connect a test light between No. 4 cylinder glow plug and ground. The glow plugs are connected by a flat, coated busbar, located near the bottom of the cylinder head.
- Turn the ignition key ON ; the test light should light, then go out after 8-30 seconds.
- If there is no voltage, go to Step 7.
- To test each plug individually, disconnect the wire and remove the busbar from the glow plugs.
- Connect an ohmmeter to each glow plug connection or use a test light. Each plug must have continuity to ground. The engine will probably start with one defective glow plug, but it will make a lot of smoke.
- To test the glow plug control system, remove the glow plug relay from the bottom right socket of the main fuse/relay panel.
- With the ignition switch OFF , there should be 12 volts at terminal 30 on the socket in the panel. Terminal 85 should have continuity to ground.
- Disconnect the stop solenoid wire from the pump so the engine will not start. With the ignition switch ON , there should be 12 volts at terminal 86. When the starter is operated with the ignition switch, there should be 12 volts at terminal 50.
- Install the relay and disconnect and ground the temperature sensor wire. Connect a voltmeter or test light to the glow plug busbar.
- With the stop solenoid wire still disconnected, operate the starter with the ignition switch. There should be power to the glow plugs.
- If all voltages at the socket are correct but there is not power to the glow plugs, the relay is faulty and must be replaced.
REMOVAL & INSTALLATION
- Remove the busbar connecting the glow plugs and determine which plugs need replacement.
- Remove the defective plugs.
- When installing new plugs, tighten to 22 ft. lbs. (30 Nm).
Diesel glow plugs have an air gap much like a spark plug to prevent overheating of the plug. Over-torquing the glow plug will close the gap and cause the plug to burn out.