I have a 91 12 valve that is running very high oil pressure. I am told that the normal for the engine is between 20 and 40 psi but mine is runnin about 70 when its cold and stays about there when the engine is hot. I am not by any means a diesel expert. Any advice on the could be wrong and how to possibly fix it would be greatly appreciated.

 

Has it ran this way ever since you've had it? How long? Or did it all of a sudden shoot up one day? If so, do anything different to it?
High pressure isn't always a reason for concern, but a sudden increase may indicate a problem with the pressure release valve.
Usually in higher mile, older engines, the pressue will drop over time. I guess I'm curious, if it's been there since day one, I wouldn't worry about it. It has to get a bit higher before it causes problems. At 150 it can deform your filter and cause the gasket to leak. That's pressure.
Let us know.
Heath

PS. I just checked on my 94 and the valve opens at 65psi, so if this is a recent change in pressure, I might take a look at the valve.