[coblanchard]

I am not familiar with how the suction tube attaches to the oil pump, but if it is loose it would suck air and cause problems. Also the relief valve could be stuck open. Just thoughts off the top of my head.

 

[coblanchard]

check out this thread, i listed what the manual says about low oil pressure and the lube system operation.
http://www.cumminsforum.com/forum/3rd-gen-powertrain/148601-no-oil-pressure-not-sender-thing.html