Low oil pressure

[Muag91]

My 94 K2500 has always had a low oil pressure reading since I owned it, but I don't think its been this low before. While driving anywhere from 35 to 90 the OP reading is around 20 and while idling the pressure reads about 3-6, just touching the red. I know it's full of oil and have been running Schaffer semi-synthetic 15-40 oil. I'm not sure if it's my gauge, OP sensor, or if my oil pump is bad. Hopefully not the later. On cold mornings after starting the OP reading is around 40 while idling, the whole thing is confusing and doesn't make alot of sense.

[john8662]

Been in this situation, well similar. The first thing you should do is replace the OPS, that way you know thats out of the way, and ruled out. Second, go to the local auto parts store and buy a generic mechanical oil pressure gauge. This kit will come with plastic lines and adaptors. You will then want to hook the gauge up to either where the turbo get's it oil or on the back of the engine. But just for checking, I think it's best to get the engine up to full operating temperature and when it's reporting the really low oil pressure shut it down. Then disconnect the fitting at the turbo and adapt your oil pressure gauge to the hose that went to the turbo, and start the engine. The turbo won't be getting any oil, so you will want to do this for a short amout of time, this is just to get a reading. Let us know what you find out. I can post pics of my gauge setup tomorrow (the adaptors and all).

[DmaxMaverick]

I suggest getting a mechanical OP gage installed first. You need to eliminate the sender/wiring/gage as being the problem.

Connect into the same hole as your current electric OP gage. Compare apples to apples. Connecting it anywhere else will not yield the same pressures. If the mechanical gage shows similar to what the OEM gage did, find the cause before you fry the engine.

If the mechanical gage shows normal pressures, then replace the sender, or whatever else that follows.

[Muag91]

That's pretty much what I figured I needed to do. Do you know what the size the OPS is. I'm sure that I get the right fitting when I get the other gauge.

[Muag91]

I went to my mechanic the other day and tested my oil pressure with his mechanical gauge. My oil pressure was running around 10psi at idle and 40-45 at normal operating speed. My idle speed (250-300) is too low (according to tach)and need to get it adjusted. That would bring my idle oil pressure up. Bought new oil pressure switch and oil pressure was reading good for about 30 minutes, then went back to reading the same as the old.

Is this what the typical oil pressure switch failure is like, or do they read correctly but the switch to the fuel pump goes bad?

Thanks for any help and suggestions.