Possible Causes (California & Federal)

Insufficient glow plug "On" time will not allow enough heat to accumulate in combustion chamber resulting in a hard start condition. If glow plug system "On" time is insufficient, probable cause is a faulty wiring harness connector, bad ground connection or defective glow plug control module or relay. Look very carefully for poor connections, burnt or loose fitting pins that will cause high resistance.

• Glow Plug Control Module (GPCM) or glow plug relay.
• Power circuit to GPCM/relay (fusible links from starter relay).
• GPCM/relay to valve cover connector circuits.
• Valve cover gasket.
• Under valve cover (UVC) wiring harness.
• Glow plugs.