My 2001 XJ8 (USA - 261,000 miles) has a recurring issue. When it's been sitting for a few days, the "low oil pressure" fault comes on when I crank it the first time. It typically goes off in 45-90 seconds - just about enough time for me to start to panic. Once it's been cranked and run, the problem does not recur - and typically does not happen at all if I drive the car every day.


A simple explanation would seem to be that the oil pump is losing prime - and that the oil pressure fault occurs while it is laboring to regain its prime, then turning off once the flow is restored. I have had an oil change since the problem started and the new oil filter, while not a Jaguar or Bosch brand filter, DOES have a check valve (according to manufacturer spec), so presumably the oil is not draining out of the filter. The problem has persisted since the oil change and new filter.


Is there another explanation for why the pump would be losing prime, or another reason why this fault might be occurring? Something in the pan or internal to the pump?


THANKS

 

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regards,
Steve

 

Sounds like the oil is draining out of the filter when the car sits, there is meant to be a check valve in the filter to stop that. I heard some non genuine filters don't have that valve.

 

For the cost of an oil filter don't you think it would cheap insurance to try a different (or even expensive OEM) filter to eliminate that possibility??????????????

bob gauff

 

What brand oil filter did you use?

Even if it does have a check valve, it could be faulty.

Another possibility is that you used a grade of oil that is far too thick for your climate, and the pump can't pump it. This is a common fault on the old LR V8.

 

+1 to changing the filter.

Doesn't matter what the filter manufacturer lists as information. The problem persists
with the new filter. Change the filter.

Also tell us what brand and part number is on there now so we can all avoid it.

 

The wording is a little vague but my interpretation is that he had the fault before and after the oil change and the new filter.

The other problem with this theory is that even if the filter is empty, like when you've just changed it, it normally takes 5 seconds to prime, not 45.

I think you need a new oil pump.

 

Good point Mark. It's possible the pick up screen is blocked, but not likely. That's a fairly easy check, especially compared to tearing the engine down to get at the pump.

 

True that this problem has persisted through an oil change and filter replacement. But same filter model (Wix). What filter should I use to be confident of solid check valve so as to eliminate this as possible source of problem?

I had also considered oil weight, but I live in Memphis and the problem is happening in 40 degree weather with 5w30 synthetic.

With 260k miles on the engine, accessory items are certainly wearing out - replaced alternator two months ago - but before assuming new pump needed would like to check off all cheap fixes!

 

Wix oil filters are as good as they come. I'd be very surprised if it was the problem. But it would be worth trying an OEM one under the circumstances.

 

how do I check the pick up screen?

 

Remove the oil pan.

 

The pickup screen was the problem. THANKS

 

Interesting, thanks for the update.

 

Just read this thread: have to ask, what was blocking the pickup screen?

 

The first thing that comes to mind is chain guides and and tensioner shoes. Was the debris small plastic pieces?

 

RJ237 you are exactly right. That was the problem. Not a bad diagnosis on the forum!!!

 

I assume you replaced the tensioners???

 

Prior owner - we guessed same thing as you and pieces looked right.