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DirtyRabbit 01-20-2014 01:51 PM

oil pressure problems
Ive had oil pressure problems since I got my 01 XJ a few months ago. It drops low unless I am accelerating. But in the morning on cold days (10 degrees or lower) it has trouble starting and the check gauges light comes on with my oil pressure at zero and the motor sounds like a motorcycle like pup pup pup pup. If I turn it off and then turn it back on and hold the key in the start position longer than normal it will start ok and the oil will jump to 40. Also now when I'm idle it drops almost to 0 and rumbles like it wants to turn off? Any ideas of where to start looking?

DirtyRabbit 01-20-2014 01:53 PM

Forgot to mention, I checked my oil and its not low. I'm running 10w30 standard.

MOBBiN 01-20-2014 02:58 PM

I had the same issue when I bought my jeep... Turns out I didn't have any oil pressure. I replaced the motor. Have you had a compression test done?

DirtyRabbit 01-21-2014 07:21 AM

No not yet. Where can I get that done?

steiny93 01-21-2014 07:28 AM


Originally Posted by DirtyRabbit (Post 19606489)
No not yet. Where can I get that done?

you can pay a shop todo it or you can todo it yourself; basically you pull out a sparkplug, hold this in the hole and have someone spin the motor; the gauge will give you a number

you do all the cylinders and compare the numbers, 145-160psi is a typical range to expect

a cylinder with significantly different compression is a tell tale of issues; that could be your hard starting issue

regarding your low oil pressure; you may want to validate that your sending unit / gauge is working or not working; having it 'jump' to 40 seems odd

you can read through the forums; quite a few threads on low pressure and the xj's

Paradise XJ 01-21-2014 10:05 AM

I have to ask...what oil filter are you running? Is it orange?

DirtyRabbit 01-21-2014 03:04 PM

Lol no I got a wix one. I heard the 4.0 likes those.

tjwalker 01-21-2014 04:46 PM

First question that needs to be asked that could be related is this. Are you having to add any antifreeze to your coolant reservoir? Unexplained coolant loss on the 00-01 can be caused by a cracked 0331 cylinder head. Not saying that is your problem but I am saying that you need to watch your coolant use like a hawk. Are you aware of the 0331 head issue on the 00-01? If not, GOOGLE is your friend and you need to educate yourself about it.

First off, any low oil pressure readings on your dash gauge should be verified. Never guess or trust what you are seeing on your dash. Go to your local parts store and rent a "mechanical oil pressure gauge". They can be rented pretty inexpensively.

Remove your oil pressure sending unit (located right above your oil filter) and temporarily install the gauge there. See what the mechanical gauge reads. If your oil pressure truly is low, then you will want to perform some more testing to decide the proper course of action. However, if pressure is within spec, then replace the oil pressure sending unit as they are a very common failure on the 4.0

The oil pressure spec. for the 4.0 is as follows:

*Not less than 13 psi at HOT idle

*Between 37-75 psi OVER 1600 rpms

TEST your way to determine root cause here. Good luck and keep us updated!

DirtyRabbit 01-21-2014 07:27 PM

Coolant isn't leaking however I did just replace the thermostat. I will rent one of those oil pressure gauges and see what it reads. If it was the pressure sender I'm under the impression that it wouldn't cause any mechanical problems, just a bad reading on the dash. Just read about the 0331 Cylinder head. Now I wont be able to sleep.

DirtyRabbit 01-24-2014 07:57 AM

After doing some research I decided to put her up on a lift and change the oil pump. Sure enough the old pumps screen was full of gunk. Its 2 degrees and she started up fine this morning

The time now is 05:29 AM.

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