Where is the 1986 Ford F250 XL 6.9 glow plug system?
The 1986 Ford F250 XL 6.9L diesel's glow plug system is located on the top of the engine, specifically in the cylinder head. Each glow plug is inserted directly into a pre-chamber in the cylinder head. You'll find them arranged in a circular pattern around the top of the engine, typically near the valve covers. Access to them requires removing parts of the engine's top end. Because of their location and the need for specialized tools, glow plug replacement is best left to a mechanic experienced with diesel engines.