Had my 88 XJS about 6 months now and getting used to all the typical quirks.
Just recently noticed the oil pressure gage is acting a bit off. Since I bought the car, the pressure has been in the 75-100 area all the time. I've noticed now that the pressure gage drops to the bottom when I put on the brakes and stop at intersections and such. Once I step on the pedal, it rises back to the 75 range again. I also see that it runs around 50-75 when in nuetral or parked.
I'm wondering if I need a new sensor. As I said, the pressure seems perfect when driving or parked, only when foot on the brakes does it seem to drop.
Any suggestions>

 

I suspect a grounding problem. Remove the cluster, clean all circuit board contacts and connectors, add a redundant ground, report back :-)

I remember the gauges on my '88 did strange things whenever I turned the headlights on. The above repairs put everything right.

Cheers
DD

 

Funny you should suggest this. I recently removed the cluster to install a wood veneer cluster and had a bit of a time re-installing it. The clear coating filled all of the screw holes and I had a devil of a time getting it to fit. I must admit at the end I basically had to force it back into place! I could barely get the terminals back in place. Probably didn't get it right.

 

There are numerous posts you can search within this forum on your issue. Mine is the same as many here. Almost nil at a stop while warm.

 

Which in and of itself is no problem. Very common for Jag V12s to have barely any o/p at idle when warm.


Cheers
DD

 

Not sure if you are talking V12 or six cylinder here.
75 to 100 seems quite high for a V12 (can't tell on mine as the gauge is stuck) but on the previous 12 bangers that I have had 50 to 70 was a good pressure.
On the 4 litre six pot that I have had I have put 3 new senders in 4 years in it.
After market stuff is *****, I am going to stick to OEM from now on.
Although the new relay for the auxiliary fan on the V12 lasted 5 weeks.
So what do I know?

 

Mine is V12
I'll probably going to remove the cluster and clean terminals at some point. Had no issues until I replaced the old fascia with new wood finished one. and could barely get the plugs back in so may be the issue.
Now on to the power steering leak!! Ugh

 

75-100 psi oil pressure is extremely high. You need to connect a mechanical gauge and measure it for real. If that is really the pressure you better get to fixing that right away.

 

It's actually running at about 75 or a bit lower. I'm having it checked when I take it in to deal with a pesky power steering leak.
I'm pretty sure it's an electrical problem. It only is affected when I put on brakes. When it's in park, Or neutral it runs at about 5-10. Then rises to about 65-70 while driving.
When I first bought the car, the gage read 100 the minute I turned the key. Now I'm thinking it may actually be reading properly!!!