Hey chaps. Lets get car details out the way first so the ADD among you can still help;
1987 XJ40 3.6 Sovereign 205,000kms

So when i bought this thing i thought it had pretty good oil pressure since the gauge would sit about half way when cruising. Then i came to the realisation it pretty much sits half way no matter what you do. Im guessing the scale is in bar so im somehow getting 4 bar of oil pressure at hot idle.

Now that just seems unlikely. Im pretty sure my old Opel couldnt even manage that and it had the highest oil pressure in the known universe!

So research has shown that on the later cars, Jag recalled them and swapped the gauge sender for a resistor and switch. Clearly this is the setup my car must have. Ive had a search around but just cant find some conclusive answers to the following;

Question is: Did any of the digital dash cars have a functioning gauge? I'd like to actually have a meaningful display rather than an extravagant idiot light.

 

In a word, YES.

Our 3.6 terror had that feature, so obviously had the original variable resistance sender unit. It never leaked, so being un-broke, was never messed with.

The dash gauge went to 1 digital strip at HOT idle, and about 1 strip past half way running on the highway.

I reckon the OE variable sender units are still available, and since your down this way, try JagDaim in Melbourne, Bill or Doug should be able to sort that fairly easily.

One of these days I will sort that stupidity on my X300.

 

If you want a truely reliable gauge install a mechanical unit,you have to put a tee fitting between the sending unit and oil galley,then feed the tube into the cabin and place the gauge where you want it.This way you also have the original electric gauge as well.

 

I heard rumours that the instrument packs got re-programmed when the sensor mod was done. This true? Or only applies to the later dials?

Would suck to spend 20 quid on a sensor only to find it does nothing.

Or maybe im better off now knowing what my oil pressure is. I might not like the answer im trying to find.

 

Not aware of that anywhere in the works.

Did a V12 XJ-S a while back, he simply refused to spend the $100+ for a sender unit, so we fitted a standard oil switch (light style), and used it to switch a relay, and fitted a resistor in the earth wire of that relay, which set the barrel gauge at near 4bar whenever pressure of anything over 7psi was present. Take into account that the V12 sender is a "reverse ohm" unit, meaning, 0 ohms = full scale, and 450?ohms = zero pressure on the dash unit.

This is what Jag did with the V12's of later production, the oil sender was a simple resisted switch and that set the dash unit to a specific value, no matter what.

Played with my X300 today, and using a variable resistor (radio volume pot), I got the dash unit to move across the scale as I varied the resistance, obviously not a "reverse ohm) sender, so maybe a REAL sender may go on the wish list sooner than later, mmm.

As for not wanting to know what is going on, why not, then the fun will begin, chasing things that really dont need chasing, or fixing. The engine is FINE, it always has been, and always will be, after all it is a JAGUAR, mmmm.

 

Will find a spare pot and test mine out on the weekend. If i can get the gauge to read right, i should be able to find an aftermarket sensor with similar output.

Failing that ill just buy a jag one. After much consideration i think i'd rather know if my oil pressure was doing funny things. Oil change is due in the next 2 months so can just slam it on when i do that.