Hi Folks, I wanted to share my experience with low oil pressure light and zero on the gauge when the engine was hot. The engine had 65,000 miles when I purchased the car and everything seemed to have been well maintained. The symptoms were.

1. At 650 rpm idle, the oil pressure was 40-45 immediately after starting the engine.

2. The oil pressure remained at that pressure 100% of the time that the engine revs were above 900 rpm.

3. In city driving the oil pressure remained constant for the first 5-10 minutes. This is long after the engine's internal temperatures had reached the normal and constant levels.

4. After 10 minutes of driving the oil pressure gauge would drop to zero and the light would come on at idle speeds.

5. Reving engine to 900 rpm or higher would return the pressure to 40 psi.

I reasoned that the problem was temperature related but not the temp of the engine but rather of the sender. I replaced the original with one which I purchased on Amazon.com here is a link $28.94

Result: Problem solved. 40-45 psi full-time even at hot temps and idle rpm.

I would also like to offer that removing the alternator provides adequate access for a 22mm wrench to remove the old unit. There is an opening from the side which is useful for removal once the device has been loosened and also for starting the replacement sender by hand. The job could be accomplished in about an hour but honestly I spent 3 hrs total, mostly trying to figuring out how to get at it.

I hope this info helps - cheers!

 

I've thought about fitting one of these "on-off" units too, as my car has the same symptoms but ideally I'd like to have a real-time sender ...I may try experimenting with a standard aftermarket unit with a 150 ohm resistor but as the bad weather has arrived it may have to wait til next spring!

btw, did you remove the sender from the engine compartment or from under the car?

Larry

 

Thanks for your report, Douglas B.

The first couple of times I replaced the oil pressure sender (once on our '88 and the first time on our '93), I did it while I was replacing the head gasket, so I had the intake manifold pulled away and access to the sender was easy.

The last time I replaced the sender on our '93, I was was able to do it blind from above, leaning over the fender, using a Crow's Foot wrench, without removing the alternator. I think I removed the MAF and maybe the air intake elbow, and that was it. By the way, I seem to recall that the sender I installed required an SAE/Imperial wrench rather than a metric one, but perhaps the wrench size varies by manufacturer.

I haven't had good luck with the senders lasting for more than several years. The original transducers all failed, and the replacement idiot-switch style senders also become unhappy after a few years. The most common problem though is oil contamination of the sender electrical connector, or oil seeping up the threads of the sender and interfering with the ground connection between the sender and engine block.

Since as far as I recall no one has ever reported an actual loss of oil pressure on an XJ40, I've toyed with the idea of disconnecting the sender and just adding a resistor from the sender's electrical harness to ground. I would experiment to find the resistor value that centered the needle on the gauge.

Cheers,

Don

 

I replaced the unit from under the car. I utilized a U-Fix-It facility that rents service bays with lifts not too far from my home. The alternator is easily removed from beneath the car. Breaking the threads loose required considerable force. I'm not sure I would have been able to get the leverage necessary with the alternator still in place. The sender isn't easy to get at from any location but being able to adjust the height of the car helped. -Cheers