Cylinder 4 glow plug assists in starting diesel engines. It sits on the cylinder head of cylinder 4. In 4-cylinder diesels, it is the rearmost plug, making access slightly tighter. It heats the combustion chamber prior to cranking. A failed plug on cylinder 4 will lead to unburned fuel during startup, causing misfires and white smoke.
Mechanic Glossary
4 Glow Plug
The electric heating element located in the combustion chamber of cylinder 4.
Frequently Asked Questions
The engine will start, but cylinder 4 will misfire for a short time, causing the engine to run rough and puff white smoke when cold.
Disconnect the wire harness, spray penetrant on the threads, unscrew the plug with a deep socket, and install the new one to factory torque specs.
It is located at the back of the cylinder head, near the firewall, where hand clearance is minimal.