I have a 2001 cummins. I start my truck my rpm gauge works for about 5 to 10 seconds then stops. All my other guages work But that one. Any idea what I can do to fix it.

 

Had Same problem with mine. Rpms would work then go to zero then come back up. But truck ran fine. Read somewhere it was crank shaft position sensor, was like 50 bucks replaced that and rpms/tach has worked ever since.