It was running and suddenly froze in the idle position. With the linkage disconnected I can click it on and off, but it will not move off  idle. what should i be aware of if I open it up?

 

Sounds like the idle lock has kicked in for some reason. OM knows more about these than anyone but it is a hydraulic lock that is activated when there is no oil pressure. Releases when oil pressure is up. If you have good oil pressure then it might be a blocked line or an internal leak in the actuator at the back of the governor. Its in the end cap of the governor on the end of the injector pump so you don't have to dig too deep.

Thanks! I will check the pressure soon as I get the batteries charged up from sitting all winter.

That it! it works fine with the engine running
if i had know that i could have saved a frozen  battery over the wiinter. (replacing it was an adventure in itself for 1 guy with a block & tackle!)
i had the bell crank assembly off for rebuilding (just finished that) and when i couldn't turn the lever on the rack i assumed it was frozen.
so thanks for the tip, you save me a lot of grief.