GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2008 🢒 TopKick C-Series (Conventional) C4/C5 🢒 Engine 🢒 Engine Controls and Fuel - 7.8L (LF8) 🢒 Glow Plug Replacement

Inspection Procedure

The glow plugs can be tested in 2 ways:

   • 
  • Perform an amperage draw test with an inductive pickup lead at each glow plug. The rated amp draw should be 6.0-7.5 amps per glow plug. Or install the inductive current clamp around the glow plug power supply wire. Take the system's current draw reading and divide the reading by the number of glow plugs in the system.
    •    • 
    Object Number: 736696 Size: SH
  • A continuity test can also be made with an ohmmeter between the glow plug lead and ground with the buss bars removed. If no continuity exists, the glow plug will not heat and should be replaced.

    • Removal Procedure
    1. If required, remove the engine cover. Refer to Engine Cover Replacement.
    2. If required, remove the air cleaner layer. Refer to Air Cleaner Assembly Replacement.
    3. Disconnect the negative battery cables. Refer to Battery Negative Cable Disconnection and Connection.

      4. Object Number: 736696 Size: SH
    4. Disconnect the glow plug power supply wire.
    5. Disconnect the glow plug buss bar.
    6. Remove the glow plugs from the cylinder head.

    Installation Procedure

      Notice: Refer to Fastener Notice in the Preface section.

    1. Install the glow plugs to the cylinder head.

      2. Tighten
      Tighten the plugs to 20 N·m (15 lb ft).

    2. Install the glow plug buss bar.

      Tighten
      Tighten the buss bar to 1.2 N·m (10 lb in).


      Object Number: 736696 Size: SH
    3. Connect the glow plug power supply wire.
    4. Connect the negative battery cables. Refer to Battery Negative Cable Disconnection and Connection.
    5. If required, install the air cleaner layer. Refer to Air Cleaner Assembly Replacement.
    6. If required, install the engine cover. Refer to Engine Cover Replacement.