AFMan

So, when I'm driving the oil pressure fluctuates up towards 40 when I'm accelerating, and lingers between 30-40 when I'm tooking along at normal speeds. When I stop at a light, it idles ride around 10, then abruptly drops causing a "Check Guages," indicator to come on. As soon as I accellerate, the light goes off and the pressure comes back up. What's going on?

I already replaced the Oil Pressure Sending Unit, and that didn't seem to fix the problem. Any thoughts anyone? Thx

Purp

Try a mechanical guage. Drive it around and see if your pressure reads normal. If not, then try an oil pump. Then if that doesn't work, drive it till it blows and buy another motor. I'm going through the same thing and I've just decided to drive it. If it blows, oh well. Another motor it is.

UserID6095

You can check it with a mechical gauge. Another thing to check would be compression, it will let you know what kind of condition the rings and valves are in. These tools can be rented from your local auto parts store.

The problem may be that the oil pump is failing and will need to be replaced. A simple but non permanent solution is to run Lucas Oil stabilizer, it should help bring up the oil pressure.

ebarnett

I just noticed my oil pressure to be off today also...When I start my jeep up and drive a little while it stays in the middle..when usually its less than that...then when I get on the highway its fine again...pressure lowers when I'm going slower speeds...but when I start it up and drive for 10mins or so it stays in the middle...I don't know--the whole thing is starting to fall apart on me this week.

ken72

Your sending unit could be going bad.... Keep an eye on it. It if keeps going up in pressure then its probably going bad, that happened to me last month. Its easy to replace.

As for the OP... I agree with the other guys. Although I dont know if I would drive it till it blows... they never just blow near the house... so this is not something I would want. A new motor will cost you more than a possible repair.

AFMan

I know how to do a compression check, so how do you to a oil pressure check with a mechanical guage?? Otherwise, everyone's advice is great, and I'll look into replacing the oil pump.

ebarnett

Yea Thanks Ken

thecrew2999

yeah i had my oil pressure jumping all over and i remember the past owner had cut and spliced a wire so i assumed it was nothing............................

till i was driving and heard dry valves tapping away looked at the gauge reading 0 pressure drove it 20+ more miles because at this point didnt care.

when i got home took the oil pan off expecting the oil pump to be shot and then noticed the oil pickup was full or what appeared to be the PCV part of the valve cover is what we came up with.

cleaned it all out of the pan and pickup ran fresh oil in it and i was seeing 40 plus psi again...

kinda feel bad for it tho because before i started was seeing 50 psi on warm oil..

i could tell the damage was done but i got a 4.0 sitting on the engine stand right now with a 4.2 sitting in the corner

also now its smoking something bad out of number 5 which that plug i dont even bother changing because its had oil coated on it and ive tried 5 times now cleaning it... neat thing is i got 175 psi on compression test on all 6...

i dont know if the oil control ring is shot or just stuck with gunk this engine is nasty inside so i ran cleaning crap which each time get massive amount of gunk out but its always there... o well 4.7 stoker in the works

thecrew2999

also i forgot to add...

the oil pumps from what i seen and heard in the 4.0s dont really slowly fade off like that..

they fail at the shaft part that connects to the distributor which is driven off the cam..

i got a pump in my garage right now that has the shaft broke with the 2 ears laying on a rag..

from what the past owner told me the distributor got tight and this happened which i dont really get it but whatever...

if you plan to replace the oil pump spend the little extra to get the high volume pump its got 25% more volume so theres no worry over oil flow in the future

AFMan

Really good info here thanks. I'm checking mine mechanically today, and if it is bad, I wonder if NAPA or other autoparts stores have a high performance oil pump?? Can you provide a part number? Thx

thecrew2999

no sorry gonna have to look around online to find the part numbers but from as i recall you can call them up and ask them for it i think they will find it for you

AFMan

Well, I mechanically checked the fuel pump, and it checked out fine(15lbs pressure). The engine isn't in anyway indicating somethings wrong, so with the sensor being changed, it mechanically checked, I'm not sure what's causing the guage to act like that. I wonder if it is my bearings or something. Anyone have any thoughts now?