2007 Liberty KJ Factory Service Manual 8 - ELECTRICAL

PLUG-GLOW

DESCRIPTION



CAUTION: The glow plug system is a 7 volt system. The glow plugs DO NOT tolerate any over voltage. Full battery voltage will destroy the glow plug immediately. DO NOT test the glow plugs with a 12V source as damage will occur to the glow plug.

CAUTION:

  • Never bend, bump or knock the ceramic glow plugs.
  • Ceramic glow plugs must not be handled loose in a container. Store, handle, and transport them only in original boxes.
  • If there is any doubt about the proper condition of a glow plug, do not use it anymore.
  • Do not clean the glow plugs with abrasive or aggressive media.
  • Avoid dipping the glow plug into fluids.
  • Read Diagnostic Trouble Codes (DTCs). If a glow plug problem is indicated, do not start the engine.

CAUTION: Disregarding these instructions may cause severe engine damage.

Glow plugs are used to help start a cold or cool engine. The glow plugs will heat up and glow to heat the combustion chamber of each cylinder. An individual glow plug is used for each cylinder. Each glow plug is threaded into the left side of the cylinder head below the cylinder head cover/intake manifold.

OPERATION

CAUTION: The glow plug system is a 7 volt system. DO NOT test the glow plugs with a 12 V source as damage will occur to the glow plug(s).

The Engine Control Module (ECM) monitors various engine sensors. When the ignition key is turned to the ON position, the ECM sends a signal to the glow plug module to turn on, and cycle, the glow plugs for a pre-determined amount of time, plus illuminate the glow plug light in the instrument panel. Once activated, the element inside of the ceramic core of the glow plug begins to glow. Each glow plug draws approximately 8amps, for a total system amperage of 32 amps at 22° C (72° F) ambient temperature. If there is a fault with the glow plug system, the ECM will store a fault code.

DIAGNOSIS AND TESTING - GLOW PLUGS

CAUTION: DO NOT start the engine before the glow system test correctly.


1. Measure the electrical resistance of the glow plug in the installed condition, resistance should be less than 0.8Ω. The ground contact must be as close as possible to the glow plug contact to avoid introducing errors in the measurement.
2. If the resistance is out of tolerance, remove the glow plug and check it again separately.
3. Use the actuator test function for the glow plug module and glow plug lamp. The design and function of the glow plug module tests each glow plug to check the complete glow system.
4. If MIL is OFF and OBD has not recognized a malfunction of the glow system, testing is finished and the engine can be started.
5. If MIL is still ON, check the electrical connectors of glow plugs and power up the glow plugs again.

REMOVAL

CAUTION:

  • If necessary, remove hindering components to ease access.
  • Do not bend, knock, or drop the glow plugs while handling (any mechanical impact may damage the glow plug).
  • First loosen the glow plug with a wrench then screw it out by hand or with assistance of a flexible tool (e.g. with a rubber hose).
  • Compare the removed glow plug with a new one. If there are missing parts of the ceramic heating element, remove all fragments from the combustion chamber before you start the engine. CYLINDER HEAD WILL NEED TO BE REMOVED




1. Disconnect negative battery cable.
2. To access the glow plug for cylinder number one, no additional components need to be removed.
3. To remove the glow plug for cylinder number two, remove the rear generator bracket.
4. To remove the glow plug for cylinder number three, remove the EGR pipe from the intake elbow and remove the intake elbow.
5. To remove the glow plug for cylinder number four, relocate the fuel filter assembly.
6. Disconnect glow plug electrical connectors.
7. Remove glow plugs from cylinder head.

INSTALLATION

CAUTION:

  • Before a new glow plug is installed, make sure that the thread of glow plug and glow plug bore in the cylinder head is dry, clean, and oil/grease-free
  • Check the resistance of the glow plug with an appropriate multi-meter, resistance should be less than 0.8Ω.
  • Tighten the glow plug by hand or means of a flexible tool (e.g. rubber hose) as far as possible and finish tightening with a correctly set torque wrench.
  • Strictly observe the required tightening torque.
  • Do not bend, knock, or drop the glow plug while installing.



CAUTION: If a fragment of the ceramic heater of the glow plug has fallen into the combustion chamber, the cylinder head MUST be removed.


1. Install glow plugs all the way into cylinder head, hand tight, until the thread stops.

CAUTION: Strictly observe the required tightening torque. If tightening torque was to high, remove and replace the glow plug.


2. Tighten glow plugs to 12.5 N·m (110 in. lbs.).
3. Connect glow plug electrical connectors.
4. Install any components that were removed for access.
5. Connect negative battery cable.
6. Test the glow plug system for proper operation before starting the engine. (Refer to 8 - ELECTRICAL/IGNITION CONTROL/GLOW PLUG - DIAGNOSIS AND TESTING)