Cummins 5.9 12 valve mechanical expert

[KRatcliff]

Originally Posted by rseibenick

Looking for help with my 1994 RV motor home with the Cummins 5.9 12 valve mechanical engine. Having issues after driving for 2hrs or more , going up even small hills.. RPM,s drop as I go up from 2200-2000-1750-1500.Few seconds later RPM goes back up then down again. OK on level roads and going down hill. Would like to talk to some and give them more info . I was at INDY for the big go and towed a enclosed trailer. Thanks.

Double check your fuel filter. You could have gotten some algae growth in your tanks that is clogging up the filter and restricting the fuel flow. They are such simple and solid engines that few things will affect them like this, but this is one of them.

I had an almost identical situation years ago with a 1997 12 valve RV. It was algae clogging up the fuel filter.