Glow Starter Removal

• Weak glow plugs can cause a diesel engine to run properly initially, then die once the glow plug starter is removed. Under such circumstances, the glow plugs are too weak to produce sufficient heat to warm the engine and should be replaced.
  
  

Partial Coil Glow

• A glow plug coil that only glows through half its length can produce only partial heat and requires replacement. The coil can be checked by placing the glow plug driver on the coil and watching how much of it illuminates.
  
  

Leaning Coil

• An off-center coil, or coil leaning close to or touching the side of the plug, will not produce sufficient heat due to the contact with the plug body. Leaning coils often indicate an engine running on a lean mixture, or a high percentage of air in the air-to-fuel combustion mixture. Adding fuel to the mixture and replacing the weak glow plug typically resolves the issue.