Glad I saw this post just now, as I am experiencing the same thing happening. Some times it starts right up and then try again and nothing. All I might hear is a click when I turn the key off.

Some history: I have been pouring tons of time into this girl

New glow plugs
Rebuilt injectors
IP seals replaced at same time
Recent new battery
Replaced ground strap on motor
Harness wire replaced as it shorted out and I almost had a barbaque
New harness housing
New 50 AMP GP fuse
Removed and cleaned fuel tank and new strainer
All new filters
Resealed Vacuum pump
New radiator
New alternator brushes
New copper fuses

I purchase lots of stuff from Kent Bergsma (Moly, rebuild kits, hoses, connectors, tools. etc.) I know a little pricey at times but usually worth it in what you get the added knowledge you receive with the parts.

I purchased a new ignition switch. and electrical switch connector for it. But cannot seem to see how it could be even remotely possible to replace them. At this point I am totally stumped. Maybe one of you could throw me a bone here?

The 2 terminals in the fender idea would be a help for me to diagnose the starter at least. Have to work by myself on this! Some direct anyway would be a help. Stumped like Mike