91 W250 I/C Cummins,isn't the oil pressure switch right behind the P/S pump on the side of the motor? My psi gauge is acting goofy and my last CTD done the same thing so I'm going to replace the swtich.

Then on the same rig I'm having a problem with the fuel gauge. The gauge itself is jumping around a good bit while driving. Sometimes I'll fire it up and it'll move right up to where it needs to be on the gauge. Then sometimes it'll stay pegged way past E like it's not reading at all. Then slowly while driving it'll start climbing up again then it'll fall back down. I wouldn't figure the sending unit is completely bad because if it was it would stay screwed up. If the little baffle had a hole in it and filled with fuel it would stay pegged past E also probably. Could it be a bad connection somewhere? I'm just wondering because having a working fuel gauge is just a pet peeve of mine.

Thanks yall

 

I would get your oil pressure sending unit from dodge or cummins. I put a NAPA one on there and not only did it read WAYY too high all the time, but started leaking in about 200 miles. I bought one from dodge, no leaks and proper pressure readings.

 

The fuel gauge sounds like a loose connection. Open circuit = empty. Short to ground = full.