Engine Electrical
Glow Plugs
Glow plugs heat the combustion chamber so a diesel engine can start, especially in cold weather. We list 31 glow plugs and related parts from $9 to $313 for engines from 1982-2021, from AC Delco, NGK, Beru and Standard Motor Products, with fits for the Chevrolet Silverado 2500 HD, Ram 2500 and Volkswagen Jetta.
Shop glow plugs by vehicle
What glow plugs do
Diesel engines light fuel with heat from compression, not a spark. In a cold engine, the glow plugs warm each cylinder so the first firing strokes happen quickly. Many engines also keep the plugs on briefly after start to cut smoke and noise.
Some diesels, including many Cummins engines in Ram trucks, use an intake grid heater instead of glow plugs. Grid heater parts also appear in this category, so check which system your engine has.
Signs of worn glow plugs
Hard starting in cold weather, long cranking, white smoke and a rough idle right after start are typical signs. Many vehicles set a glow plug circuit code and flash the glow plug light when a plug or the controller fails.
You can test each plug's resistance with a meter. A plug that reads open has failed. If several are weak, replacing the full set is common, since they wear at similar rates.
Choosing and installing
Match the engine code and year, since thread size, length and voltage vary. Listed lengths here include 5.39 in and 5.86 in plugs, and some listings are 8 piece sets for V8 diesels.
Glow plugs can seize in the head, and a snapped plug is a costly repair. Work on a warm engine where the maker allows, use penetrating oil, turn slowly, and stop if the plug binds. Torque new plugs to specification, as overtightening can damage the tip.
Glow Plugs questions
Should I replace all glow plugs at once?
Many owners replace the full set because the plugs age together and removal takes time. If only one plug failed on a newer engine, replacing that one is also reasonable.
Can a diesel start with a bad glow plug?
Often yes in warm weather, but cold starts get harder and the engine may smoke and run rough until warm. Several failed plugs can stop a cold start.
Do all diesel trucks use glow plugs?
No. Some engines, including many Cummins diesels in Ram trucks, use an intake grid heater instead. Check your engine before ordering. The fitment table shows which parts match your engine code.