GM Full-Size Trucks 1980-1987 Repair Guide

Glow Plugs

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DIAGNOSIS



379 (6.2L) Diesel Engine

See Figures 1, 2 and 3

Many times a problem in the glow plug system can be attributed to a loose or dirty electrical connection. Perform the following checks before proceeding to the preliminary diagnostic chart.

  1. Check all connections on the controller.
  2.  
  3. Check the upper copper stud nuts on the controller. Do not tighten them.
  4.  
  5. Check the engine harness ground connection and the wiring harness nuts. Tighten them to 8 ft. lbs. (11 Nm).
  6.  
  7. Check that the four-wire connector at the controller is seated properly and latched.
  8.  
  9. Tighten the controller mounting nuts to 35 ft. lbs. (4 Nm).
  10.  



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Fig. Fig. 1: Glow plug system schematic, 379 (6.2L)



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Fig. Fig. 2: GLOW PLUG PRELIMINARY DIAGNOSIS CHART, 379 (6.2L)



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Fig. Fig. 3: GLOW PLUG DIAGNOSIS CHART, 379 (6.2L)

350 (5.7L) Diesel Engine

See Figures 4, 5, 6, 7, 8 and 9

Many times a problem in the glow plug system can be attributed to a loose or dirty electrical connections. Be sure to check that the electrical connections at the glow plug controller, glow plug relay, glow plugs and the temperature switch are clean and tight before proceeding with the diagnostic charts.



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Fig. Fig. 4: Glow plug system schematic, 350 (5.7L)



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Fig. Fig. 5: GLOW PLUG DIAGNOSIS CHART 1, 350 (5.7 L) ENGINE



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Fig. Fig. 6: GLOW PLUG DIAGNOSIS CHART 2, 350 (5.7L) ENGINE



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Fig. Fig. 7: GLOW PLUG DIAGNOSIS CHART 3, 350 (5.7L) ENGINE



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Fig. Fig. 8: GLOW PLUG DIAGNOSIS CHART 4, 350 (5.7L) ENGINE



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Fig. Fig. 9: GLOW PLUG DIAGNOSIS CHART 5, 350 (5.7L) ENGINE

REMOVAL & INSTALLATION



Glow Plugs
  1. Disconnect the negative battery cables.
  2.  
  3. Disconnect the glow plug lead wires and then remove the plugs. You'll need a 3/8 in. deep-well socket.
  4.  
  5. Install the glow plugs and carefully tighten them to 12 ft. lbs. (17 Nm).
  6.  

Glow Plug Inhibit Switch
379 (6.2L) ENGINE
  1. Disconnect the negative battery cables.
  2.  
  3. Disconnect the electrical connector from the switch.
  4.  
  5. Remove the switch using a socket switch.
  6.  
  7. To install the switch follow the procedure in the reverse order. Tighten the switch to 17 ft. lbs. (23 Nm).
  8.  

Glow Plug Controller
379 (6.2L) ENGINE

See Figure 10

  1. Disconnect the negative battery cables.
  2.  
  3. Disconnect the electrical connector at the controller.
  4.  
  5. Unbolt the two electrical ring terminals.
  6.  
  7. Remove the two controller mounting nuts and remove the controller.
  8.  

To install:
  1. Install the controller on the mounting studs. Tighten the upper nuts to 48 inch lbs. (5 Nm).
  2.  
  3. Reconnect the two electrical ring terminals.
  4.  
  5. Reconnect the electrical connector.
  6.  
  7. Reconnect the negative battery cables.
  8.  



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Fig. Fig. 10: Glow plug controller, 379 (6.2L) Engine

 
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