Facelift Oil Pressure is Showing Zero
 

I have a 96 AJ16.

My oil pressure gauge is showing zero. Resting on the pin zero.

How do I know the gauge has indeed failed?

There's no oil on the floor. The oil level is right where it should be on the dipstick. The engine is running at the proper temperature. No smoke anywhere.

What else can I check? Am I in any possible imminent danger?

Check the sender, that's much more likely to fail than the oil pressure being really zero. Not sure about the XJS, but on the X300 cars the gauge is really an idiot light with a switch and resistor that drives the gauge to roughly midpoint as long as the oil pressure is over a certain threshold. You could probably ground the sender with the ignition on and see what the gauge does. Should deflect if the gauge works.

I can't remember the exact location (on top of the engine I think as it was easy to get to) on my six cylinder car but it's a small part, cost me about £25 and took about 20 minutes to change.


On mine as soon as the oil reached it's ideal temperature the pressure gauge would go to zero whenever the revs would drop.


Change of sensor did the trick. My car was about 8 years old and 30,000 miles when the problem hit if that helps.

Thanks. Quick question, should I wait until I change my oil, or can I change the sensor without worrying about oil shooting out of the hole?

Swap it out at your convenience and angst tolerance.


If there were no oil pressure present, the engine would be toast, the burnt variety!!!


If the engine is not running, there is no pressure to shoot out on removal of the sender. A bit of weeping, probably.


to check the guage, remove the wire from the sender, touch it to ground, the guage should peg max OP. it probably will.


The senders are not robust. Been there done that.


Carl.

My 95 4.0 has the factory sender and gauge will move up and down as it should. I want to find a replacement for the pressure transmitter and not convert it to a switch with the resister to read mid scale all the time. That is what the oil light is for in the row of warning lights. What is the sender type you purchased? Did it come with a resister in a little wiring harness. If it did your oil pressure gage will read mid scale all the time. If it didn't you may have a real pressure transmitter and I would like the part number and brand.

I'm pretty sure the XJ40 transmitter is the same: DAC 7879. RockAuto.com shows a few choices under that part number. You might want to try Coventry West as well.

A little bit will spill, but not much. It would only shoot out if the engine was running! It should be located on the oil filter head somewhere.

Vee,

As mentioned, it sounds like either the sender or the gauge, rather than the engine. Earthing the wire on the transducer should will indicate whether its the sender or the gauge.

Remember that the pressure transducer (for gauge) is next to the pressure switch (for light). The transducer is the bigger of the two.

As you probably know, Jaguar had to move from a proper pressure transducer to a revised one that just makes the gauge sit in the middle rather than indicate the real varying pressure. This was in response to US owners complaining that the reading seemed to go up and down!!

The original part number DAC7879 was superseded to LMD5640AB which then superseded to JLM20791. If you are lucky enough to get one of the very original NOS senders, that would help you understand the real fluctuating pressure. Or if you can find an equivalent of that original sender, do please let us know.

Good luck

Paul

Yep, I changed mine with full oil in the car, no problems.


I wrapped a small amount of PTFE tape on the thread. Probably totally overkill but it at least makes sure that the thread is sealed against leakage.


I think in the end I got the part from the local dealer, only because there were so many different designs on the internet I didn't want to go to the trouble of having to return one through the post if it was wrong, wasn't much in it cost wise only a few pound.


If you want to know what it looks like....


JAGUAR DAIMLER OIL PRESSURE SENDER FITS XJ6, XJ12 & XJS 700 KNM 100 PSI C46272 | eBay

Gee, I suppose Jaguar and other makers could have merely installed a glass with a needle painted on the center.


My 83 Jaguar has a real guage. Seeing movement is reassuring, rather than worrisome.


My 94 Jeep has the stabilized version. 50 PSI, no matter what...
I've been tempted to mess with it, but have resisted, so far.....
It's old tech OHV 6 is unremarkable, but so sturdy and dependable.
Grand Cherokee, still taut, tight and shiny at well over 200K!!! Miles that is. Jaguar at a mere 134K!!! it's LT1 ???? but, purrs. It can growl a bit if prompted...


Carl

This is probably the definitive thread on the oil pressure sender/sensor as fitted to the 4.0 litre cars ...all issues incl resistor values and pro/cons of idiot light vs. live gauge are addressed here:

https://www.jaguarforums.com/forum/x...sender-133621/

cheers

Larry