Got the truck running last night and took a trip to town. When I started it today, I noticed the oil pressure went way past the pressure relief (60 psi) and pegged the meter at 100.

Would a plugged oil filter do that? Would the relief plunger stick when parked for a few months?

 

When I had my oil cooler/filter housing off to fix a leak my bypass valve fell out in pieces! I needed the truck next day so could not order a new one so I backyard engineered a fix. So having seen one in pieces I don't think it could lock up...but stranger things have happened. Changing the oil filters seems like a quick and easy 1st attempt at a fix.

 

Be sure oil pressure sender wire isn't grounding somewhere. Or possibly failed sender.

 

It's a Bourdon Tube gauge.

 

There is an redesigned oil relief valve for the oil cooler that I got from Cummins. Sorry I don't have a part number.. The cooler is a fun part to remove and reinstall but the relief valve was a piece of cake. I replaced mine when I replaced the cooler and found the oil relief wasn't closing all the way causing low pressure at idol. Sounds like your's could be clogged or stuck. When cold I see 80 pounds on the gauge that I installed on the oil filter housing next to the turbo supply. When the oil heats up it runs around 60 to 65 pounds at highway speeds. 25 to 30 at idol.