Diesel engines rely on high heat from compression to ignite fuel. On cold starts, the metal cylinder walls absorb this heat, preventing ignition. The cylinder 1 glow plug heats the combustion chamber directly. It reaches over 1,500 degrees Fahrenheit in seconds. Once the engine runs, the glow plug turns off. A failed glow plug on cylinder 1 makes starting difficult. The engine will run rough and emit white smoke until it warms up.
Mechanic Glossary
1 Glow Plug
The heating element located in the combustion chamber of cylinder 1 in a diesel engine that warms the air charge for cold starts.
Frequently Asked Questions
Hard starting in cold weather, a rough idle for the first few minutes, and white exhaust smoke on startup.
Yes, but it is best to replace them as a set. If one has worn out, the others have experienced the same heat cycles and will likely fail soon.
The internal heating coil degrades from constant heat cycles. Excessive voltage or leaking fuel injectors can also burn them out prematurely.