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Unread 02-12-2009, 10:26 AM   #1
Whtfairladyz
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Here we go again..ANOTHER Oil pressure problem

OK guys, I did some reading under the SEARCH function. And I really did not find any definitive answers. I am facing a similar problem to a few other guys on here.

(SKIP TO THE BOTTOM FOR MY QUESTIONS)

Here is the scenario:

My Jeep is a 2000 Sport 4wd I-6 with 153K miles.

A few months ago I noticed that while sitting at a red light, engine at operating temp, that my Jeeps oil pressure would suddenly drop to ZERO. The first time it did this, I shut the engine off immediatly and checked the engine out. (Expecting to find that the oil pressure sending unit or filter had taken a dump or I may have lost the drain plug). I checked the oil...PERFECT LEVEL and recently changed.

I cranked the engine back up, and the oil pressure came back up to normal.

This happens occasionally. Somedays it does this, some days it does not.

I am not burning any oil, and my oil level has always remained the same.

Here is what I have done:

1. Changed Oil again..just as a precaution
2. Changed Oil pressure sending unit...(I assumed that this was the problem)


After doing this, it did not do it for a while. But it eventually HAPPENED AGAIN, and AGAIN.

I read up on the problem and decided that since it was RPM dependant, I wanted to rule out the factory gauge being bad.

SO, I pulled the oil pan to check the oil pick-up screen and decided to go ahead and toss in a new oil pump from Melling. I cranked it up and everything has been perfect!

BTW...the oil pickup screen was clear of debris. And the pump seemed to function fine, but seemed "clunky".

Fast forward a month.....

I have not had this problem happen to me in over a month. Then suddenly, while sitting in a drive-thru. It HAPPENED AGAIN!


I am at a total loss of what to do.

--------------------------------------------------------------------------
My question: Are there any orfice valves or by-pass valves in the motor that could be causing my 0 oil pressure problem???

I know on my NIssan 300zx, there is a by pass valve on the oil filter block that bypass oil from the filter in the event it gets clogged. Since the oil pressure sending unit is attached, I am not sure if it would by pass the sending unit as well.

Thanks for your help/ insight!

Dustin

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Unread 02-12-2009, 05:19 PM   #2
AZ Jeff
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I am inclined to suspect that the signal wire from your guage to your sender is developing some sort of intermittent open connection, and it's more prone to this when the engine is idling.
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Unread 02-12-2009, 05:41 PM   #3
viper719
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Im agreeing with AZ, as it only happens at idle, Im willing to bet the vibration from the I6 idling is rubbing a short in the signal wire. time to break out a VOM and go to work.
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Unread 02-12-2009, 07:23 PM   #4
JeepRide
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Get yourself some electric spray cleaner I used mac brand 4700 spray connector and the oil switch plug couple times plu\unplug switch connector let dry for a few apply some dielectric grease to the sender plug end.This is how I fixed same problem you are having.
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Unread 02-12-2009, 09:42 PM   #5
Whtfairladyz
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THanks guys. I T'ed off the oil pressure sending unit and plumbed in a SUNPRO mechanical oil pressure gauge. If it does it tomorrow, which I suspect it will, I will have a definitive answer about my problem.

I hope it is electrical and not a mechanical issue. I ll let everyone know what I find tomorrow.
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Unread 02-13-2009, 06:25 AM   #6
tjwalker
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Some great advice here. I would bet that your problem is electrical, not mechanical. I'd sure start by cleaning the connector as JeepRide suggested. Simple stuff first. Plumbing in the mechanical gauge is an excellent idea to help in the process of elimination. Good luck and post back what you find.....
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Unread 02-13-2009, 07:56 AM   #7
440_Magnum
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Quote:
Originally Posted by Whtfairladyz View Post
I have not had this problem happen to me in over a month. Then suddenly, while sitting in a drive-thru. It HAPPENED AGAIN!


I am at a total loss of what to do.

--------------------------------------------------------------------------
My question: Are there any orfice valves or by-pass valves in the motor that could be causing my 0 oil pressure problem???


Dustin
First off, before you assume anything go ahead and take the time/trouble to install a MECHANICAL gauge- the kind with the little tube (get a copper tube if you want to make it permanent, although I've never had a plastic tube fail except when over-tightened or routed near something sharp). Ride around with that for a while and see what the pressure is really doing before you worry too much- I'm with the person who said its an intermittent electrical problem somewhere, maybe even a bad sender right out of the box (it happens).

As for valves, there is a pressure regulator valve. IF it hangs open at high RPM, then the oil pressure can drop too low when you return to idle. Shutting down could conceivably "un-hang" it.

I'd have to go look at my FSM to see exactly where the valve is in a 4.0, but they are *usually* in the oil pump casting itself, so you've probably already replaced it... which is why I'm guessing its electrical.
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Unread 02-13-2009, 10:05 AM   #8
Whtfairladyz
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Well...Now I am really confused.

I was expecting an electrical problem. But I went ahead last night and plumbed in my mechanical oil pressure gauge.

I drove to school this morning and waited for it to finally act up and read ZERO on the factory gauge. After about 20 minutes of driving, the gauge finally dropped and hit ZERO.

I immediatly checked my mechanical gauge, expecting to see a normal reading.....but I was WRONG!

The mechanical gauge was showing ~6 psi. Apparently, anything below ~10 psi causes the factory gauge to read zero.

I m going to do some more research as for the location of the valve, hopefully it is not to hard to get to.
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Unread 02-13-2009, 11:13 AM   #9
stinkshoe27
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I guess this is kind of related but I was driving my 88 yesterday for the first time on the highway and I've been pretty nervous the whole time I've been driving it so I keep my eyes on the gauges and all of the sudden on the on-ramp my oil pressure spiked long enough for the needle to peg out then dropped back to around 40 where it typically is. I'm hoping it was some sort of anomaly but there's no telling with this thing.
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Unread 02-13-2009, 11:49 AM   #10
Whtfairladyz
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From what I have been finding...talking to techs (that know XJ and MJs) and reading online. It looks like I might either have a blockage in a oil passage...or even possibly bad bearings. I honestly dont see how I have bad bearings, or too much bearing clearance, when I hear absolutely NO knocking or rattling.

I m going to flush the oil out tomorrow, do an oil change, and see if I can force air to free up whatever....just to see what it will do.

If that doesnt work. Then it looks like I might be dropping my oil pan AGAIN!

As for the pressure relief valve question I had. They are built into the pumps on the I-6 engines. So mine technically has a new one.
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Unread 02-15-2009, 07:31 PM   #11
Whtfairladyz
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Well I did two things...
First of all, i fab'ed an air fitting to plumb an airline from my air compressor into the 3/8" port where my oil pressure sending unit. I tried pumping in air pressure into there and into the dipstick tube. My hopes were to try and break loose any blockages...if any.

My second attempt was to run about 4 qts of ATF with 2 qts oil thru my engine. I was a little paranoid to run straight ATF thru it. I ran it about 30 minutes.

I drained the ATF/oil mix and changed the oil with fresh and did the Oil filter Upgrade Eric talks about in his book. (BTW...a very good read!! I picked mine up from Summit Racing).

I ran the Jeep for 30 minutes, usually about the time it starts acting up. And so far, no issues. But I am not going to claim that the problem is fixed just yet. I ll give it a test drive tomorrow.
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Unread 02-15-2009, 08:09 PM   #12
JoBo
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What weight oil are you using? With your high miles you may need a thicker oil expecially during the summer months. I bought a very clean 00 classic yesterday with 145k and intend to run Shell Rotella 15-40 diesel oil in it. (not the synthetic 5-40 that i use in my KJ CRD). I have used the 15-40 in my past 3 XJ's and had no problems. As far as engines go our 4 liter i6 is pretty crude They can have different size bearing inserts on the same rod and the same for the crank journals. On the rods the only thing you can count on it the top rod inserts being all the same. And this is from the factory I found this out when I was chasing a knock on my 150k mile 96 XJ. Also since all was good for a while after the oil pump you could just be needing a change
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Unread 02-16-2009, 10:19 AM   #13
Whtfairladyz
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I generally use 10w30 high mileage.

....and yeah right. Changing that oil pump sucked. It would not be so bad if my XJ had a lift. But sitting stock made it a PITA. My cousin's '95 would be a snap.

BTW...how do you like the CRD? I wondered if anyone has ever attempted a CRD engine in a XJ?
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Unread 02-16-2009, 03:53 PM   #14
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Quote:
Originally Posted by Whtfairladyz View Post
....and yeah right. Changing that oil pump sucked.
BTW...how do you like the CRD? I wondered if anyone has ever attempted a CRD engine in a XJ?
I put a high volume pump on a noisey 96 and it is indeed a pain dropping the pan and the bad part was it was still noisey

There's a fellow over on L.O.S.T KJ that's putting a CRD engine in a Commanche.There was a 2.5 L diesel available in XJ's for the rest of the world from 92 through 01

The CRD engine is great but the Chrysler programming on it and the transmission is worse then windoz The Liberty has better highway manners with it's independent front suspension but the fuel mileage is not what it should be but better then the 4L in the XJ. Let's just say I've bought my last KJ and forth XJ I've now got 2 jeeps in one garage His and Hers
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Unread 02-16-2009, 06:29 PM   #15
Whtfairladyz
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LOL...I have fallen in love with Turbo Diesels, especially for towing. I would love to stuff a Cummins from my company truck in my XJ if it would fit. A CRD engine just seems like a perfect match, but I have not had any luck sourcing either a totaled CRD KJ or any Renault engines. I have contemplated the Mercedes Diesel engines, but being OBD II, I want to see if I could do it and still remain legal here in Ga.
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