I've had to replace my glow plugs twice since 2004 2615HST. They are located on the right side of the motor on top. They kinda look like spark plugs. There is a common strip of metal that connects them all together with a single wire going to the first plug. The wire comes from the glow plug timer box. It should read battery voltage when the timer circuit is activated. If one or more glow plugs are shorted to ground you may not get a reading. If no reading, disconnect the wire and test again.
To check the glow plugs you must remove the common metal strip. Then you can test them in place or remove each one and test individually with an ohm meter. There should be a resistance reading between the center threaded stud and ground. They should not read open or shorted, if so they are bad.
If mine go bad again I'll order a set from Galen. According to him, the ones I got from my local dealer are the wrong number but as long as they work I'll use them.
