as long as u know how to post pics.. how about 1 of the engine & fuel system.??
Glow plugs are easy to check but u either have to have a battery charger or some wire & alligator clips OR a volt meter..
IF u have a volt meter, set it to ohms.. disconnect it from the common electrical rail it u have the type that connects them all.. Hold the lead to the top of the GP & 1 on the body.. U should read less than 2 ohms.
anything over & its bad..
IF u DONT HAVE a volt meter, ur gonna hafta takem out.. apply 12v + to the TOP & - to the body.. it should get cherry red in less than 10 seconds..
IF 1 or 2 test bad, REPLACE THEM ALL.. & keep the "good ones" as spares..
Let us know how THAT turns out & we can go from there..
OH, MAKE SURE your getting power TO THEM when u turn the key or push a button..
Good luck.