Hello,

Reciently picked up a mid 90's Dodge Ram with the cummins 12 valve with about 240k miles on it. No history to speak of as to what if anything has been done to engine. In looking at different blogs etc. different views are presented as to what proper oil pressure should be present on their diesel engine at given temps, RPM's etc.

Sadly, on this particular truck, it seems most everything on these trucks break/fall off but the older cummins 12 valve engine will keep ticking after the truck itself has fallen off

Because the dash guages are intermittent on again, off again and just like some others have said, don't trust the dash gauge as it reports a higher than reality oil pressure and is not accurate which is true, as when it does read, it says about 40psi regardless of cold, hot, idle or running (what a laugh) have also noted that this engine tends to have low oil pressure, so here's my question.

Is it possible this cummins engine has had a recent rebuild done? (immediate prior owner didn't know) and the intake manifold is pretty badly rusted over. I put a manual oil gauge on it and the gauge is working properly. At cold start (i.e. 50oF out), pressure at idle is 80+psi. After engine warms up and is driven a bit, the pressure at idle is still about 30psi and on the road anywhere between 45 to 55 psi. A young cummins diesel mechanic I was able to talk to briefly a while back confirmed that the older cummins tended to have lower oil pressure and was amazed at the oil pressure I am getting and this IS with a large bypass filter on the engine. This engine which does not have glow plugs but has a intake heater, will quickly start even when about 32oF out and having set dormant for weeks.

I would think this would be 'average' / ok for most any engine in excellent condition. Has anyone had experience with the older cummins 12 valve? Since diesels in general have such a long life, I would think that a diesel should have pretty good oil pressure, but then I'm a bit new to the diesel world.

I'm sure feedback on this and other popular diesels regarding oil pressures to expect when new as well as when older might be beneficial to those needing to get a feel for what their diesel should be doing.

Thanks!

 

I have seen 12 valves with over 300k that have that oil pressure, I have seen some with 50K on them that dont. The only thing I know from working on my 12 valve is if you use a 24 valve oil pump (direct bolt in) you will have much better oil pressure, maybe someone has done this to your motor. P.S. make sure your killer dowel pin has been tabbed.