The cylinder 9 glow plug preheats cylinder 9 to assist in starting diesel engines. It sits on the cylinder head. If the plug fails, cylinder 9 will misfire when cold. The engine will run rough and puff white smoke on cold mornings until it reaches operating temperature.
Mechanic Glossary
9 Glow Plug
The electric preheating element located inside cylinder 9.
Frequently Asked Questions
Hard starting in cold weather, rough idling, and white smoke from the exhaust on startup.
Unplug the wire harness, spray penetrant on the threads, unscrew the plug with a deep socket, and install the new plug.
Carbon buildup on the plug tip can seize it in the cylinder head. Always spray penetrant and use a torque wrench to avoid snapping it.