oils pressure switch ?

96 JGC 4.0 6cyl @124k
ok so here is my plightf of wackey oil pressure ..

It started sometime ago... after driving for @ 20 min when truck was at idle the pressure would drop to 0 ( according to gauge) than when i hit the gas it would go back up ..


so i had the oil pressure gauge checked and it was at 30

on friday i had a new oil pressure switch installed...
pressure reads 50 or so ( gauge in car) but when i come to idle ..

NOW WHEN I AM AT IDLE AFTER DRIVING FOR @ 20min THE GAUGE WILL GO UP TO 80 until i hit the gas than it will settle back down.. so its doing the exact opposite of what it was..

UGH ! ANY THOUGHTS ?

My jgc had an erratic oil pressure reading too.

I eliminated all of the electrical and mechanical causes except for the pressure regulator.

The indicated increase in pressure could be the result of a sticky regulator valve. I mostly cured mine by flushing the engine prior to draining the oil for several oil changes and then ran rislone for one oil change period. Drained that at the oil change and installed mobil1 10/30. Normal oil pressure has improved and the unexpected gauge fluctuations have virtually stopped.

Just my experience.

JD

JD what is RISLONE?

One of the two additives that I will use for special drastic circumstances only. A short term fix to try when all else has been tried.

http://www.rislone.com/engine.htm

JD

ok, I have never heard of it, so I didn't know what the heck it was. does it seem to work good?

well I just read the info on the link u sent, and it seems to be a good thing, I used that new Gunk-Motor Flush, and it worked good but all the sludge that was cleaned off the engine end up in the bottom of my pan and didn't all drain out when I changed the oil , and it end up clogging my Oil Pump screen. so 2 days later I had to drop the pan (which if anyone has done it, knows it's a bitch) to clean the it out.

well I just read the info on the link u sent, and it seems to be a good thing, I used that new Gunk-Motor Flush, and it worked good but all the sludge that was cleaned off the engine end up in the bottom of my pan and didn't all drain out when I changed the oil , and it end up clogging my Oil Pump screen. so 2 days later I had to drop the pan (which if anyone has done it, knows it's a bitch) to clean the it out. I think I am deffinately going to pick-up some RISLONE b4 my next Oil Change and try it.

Depends on what you are expecting out of them.

Like I said, one of the two additives I will use. The other one is GM or Chrysler's Engine oil supplement (EOS)

They are the last resort before I go in deep.

Otherwise it's just the oil in the crankcase.

JD

Thats the problem with used vehicles. You get the problems caused by the previous owners lack of knowlege/maintenance.

What were the operating instructions with the Gunk engine flush??

JD

pour the whole quart in the cold enigne at the time of the Oil Change, then let the engine run for 5 minutes (Idle, do not drive), then continue with the oil and filter change.

Thanks for the info will try that but think i have more of an issue going on .. possibly electrical ...

when the oil pressure gauge really start getting wacky ( and this is justwhen warmed up ) the car will more or less just not go ... i hit the gas and it feels like it going to die... I also have on occaion been hearing some "back fire" in engine ...

could this be an o2 sensore like in prv post ? or does this soun electrical .. it only does it when after driving for @ 20 - 30 min

I was trying to find the answer to this same problem. I went on the internet and did a few searches, there were plenty of people with similar problems which they could not find the answer to. This is obviously because nobody took the time to come back and post their findings (gee..thanks for sharing). Since nobody helped me out, I thought I might help others with this frustrating and annoying problem. Keep in mind, this was MY problem, and may not be yours..but for the price below, give it a try.

Oil sending unit. Low oil Pressure Problem. 1996 Jeep Grand Cherokee 4.0 150,000mi. The engine sounds and runs as if it has 30,000 miles on it…she’s is t-i-g-h-t. The problem was after driving for longer than about an hour, the oil pressure will drop to zero when coming to a stop. Like in city driving and coming to a light. Or HWY driving and getting off at an exit and coming to a stop or near stop. The oil pressure would suddenly drop from 30psi to zero. The check engine light would come on and a tone would sound. But anything over 2000rpm’s and it is fine. It reads 40+ lbs at 70mph or 2000rpm otherwise. I had this problem for several years, but it was rather intermittent, sometimes not happening for months. I would just shift into neutral and rev. the engine a bit, and up it would swing. I run 10/50w oil being in Florida. I tried switching to 10/30w, it “seemed” to get worse, and of course this was nothing I wanted to experiment with. This problem did not happened on short trips only on longer ones. But recently the problem became a little more frequent I had to investigate since this is a potentially SERIOUS problem.

Possible problems were oil pump wear, crank bearings, cam shaft bearings, oil pressure valve and a couple others, but it only did it every now and then….the above would have happened quite a bit more frequently I’m sure.

SOoooooo, I decided to inspect the oil pressure sending unit. This is located just above the oil filter, its round, plastic and silver, with two wires running into it, you can’t miss it. I unplugged the wires from it, and low and behold, there was oil there the male/female connectors came together..surely this can’t be right I thought.

I shopped around, I got prices of $50.00 for the first two phone calls, and $30 on the 3rd call at AutoZone. Drove home (problem happened again), installed new sending unit in, drove around, noooooo problem !!!

I decided to take a hacksaw to the old one to see if and how much oil was in the internal part of the sending unit chamber, or if there was supposed to be any there. I started cutting like a bologna slicer, it was filled with oil. I finally cut right where the plastic and metal join. BINGO, there was a plastic/neoprene gasket in there that is MEANT to separate the oil from the electronic parts. You see, oil is force in the small hole, and then this membrane is supposed to flex and press on the electronic portion giving a reading. The neoprene gasket was leaking!!

Problem solved. Ready for another 100k I’ll bet.

Yeah believe me, you aint the only one with this problem. My 96 limited 5.2 does the EXACT same thing, and we have changed sooo many things we basically gave up, and we have come to the conclusion that it is a fault in the guage itself in this year jeep. Too many people are having the same problem, but, do any of them tell you of engine failure? Nope, it's mostly like mine, just falls to zero at stops, and then goes back up, but not before giving you that pleasant buzzer to deal with, sometimes 3 to 4 times while you are sitting there. Does anyone actually have an answer to the problem, my next thing, like I said, is I'm going to pull the guage and replace it. I noticed that right after oil changes it tends to quite down for like 1 DAY!!! This just doesn't work for me, and it's like a lifetime goal to find the problem and fix it, cause my jeep is just in too good of condition and I got too much money into it, so selling it just isn't an option. I'm sure I'm like most of you, and that is just out of the question!!! I'll keep ya posted...Any new findings, please email me and let me [email protected]

if u have changed the Oil Pressure Switch and it did not help, then it may be the Oil Pump. - the screen could be partially clogged, and may need to be cleaned, or the gears in the pump are worn and not pushing enough oil at low speeds.

that a coupl ethings to look for.