Yesterday my 2009 diesel X400 suddenly decided not to start. Turned key but nothing happened; no solenoid, no dimming light etc. After some time I decided to give the fuel emergency cut off valve a push; after that everything started as normal. The diesel does no have an electric fuel pump to shut off and investigation of the wiring diagrams are not very helpful in showing what this switch does inhibit. I however today decided to disconnect this switch and it produced the same symptoms. I have now ordered a new switch in case the same thing happens again.

 

Fault now fixed. When the fault is present there is no continuity from F34 in engine fusebox to ground. This was caused by a "dry joint" on the starter motor.

 

Well, there is dry ............and then there is downright arid!
Good find Richard.

 

The pain in the butt was having to completely remove the starter motor to find and fix it.