1983 300Sd Engine turns but will not start. Symptons were
1) the glow plug light takes about 5 seconds to come on stays on for a few seconds and then goes out. After 21 seconds I hear a click. Does this sound normal?
2) Had some nailing. Ran Diesel Purge through. Ran great for a few days and then the slight nailing came back at low speeds.

I intend to change the glow plugs (about 80,000 miles on them)and relay along with the injectors (over 100,000 miles) should there be anything else I need to be looking at? Valve adjustment or timing chain?