LOW OIL PRESSURE

Well we need a little more info such as what engine, and millage. Has it always done this or is it something that just started.
What is the oil pressure at cold start?
If it falls off how long does it take?

 

OK the C7 is a HUEI engine. It uses oil pressure to set the timing and fuel rate. Basically the pressure you are seeing is lube oil which also supplies the high pressure oil pump. There are so many causes without seeing touching and feeling it, it would be hard to give an answer that is spot on. I would change mechanics first and foremost without fail immediately. Yes the C7 is notorious for dirty oil to cause lots of glitches but one oil change does the trick. Most truck guys have little to no experience with them where as equipment techs see them often. I would do some home town research and if all else it may be time to take it to CAT. Less than 5 psi isn't a huge deal but something tells me there is more to it

 

I'm far from an expert, but with your engine being @300k miles chances are it's burning oil a little faster. Have you checked the oil level itself? Is it consistent with where it was at the time of change?

You may simply need to add a little to make up the diffrence. Less oil would account for a small dip in pressure.

 

Don't run out and buy an injector or a set, don't tell a shop you suspect it needs one cause they will throw a set at it. One of the more common problems is an injector sticking on the mechanical side dumping oil out the return to fast and its hard for the pump to keep up. I wanna say they had some minor suction tube issues in the pan too which would be cheap. Also there is an oil filter bypass valve it is designed to open if the oil filter becomes stopped up as dirty oil is better than no oil. It or the relief valve may have a small piece of trash or metal on it causing it to stick open. Again a cheap easy fix like I said just hard to know without seeing

 

I would put a gauge on the block to verify pressure & I replaced spring in my oil pump & springs in oil filter housing all is well now. I hope all works out for you.

 

First step is to verify the oil pressure with a good mechanical gauge. Your oil pressure gauge may be stand alone, meaning that the engine didn't come with one and Kenworth added a sensor just for the gauge. Sounds goofy, but many fleet HEUI engines did not come with an oil pressure sensor simply because without oil pressure it wont run, low oil pressure usually makes it run bad. Low oil pressure will still cause a check engine light for low actuation pressure sensor.

If you need the shop manuals for C7's, PM me your email address and I can send them to you.