This question pertains to the same car in the A/C thread...

Bought it yesterday and drove it home. The oil warning light never comes on, but the gauge is showing a very low reading. I'm not completely sold on the integrity of the gauge cluster as a whole -- fuel tank needle won't go beyond 3/4 full even on a full tank, voltmeter needle moves up or down in steps sometimes rather than smoothly -- but I don't want to do a lot of driving until I'm sure the car is OK.

I will say that the car is a super-strong runner, the strongest V12 I've ever come across, and exhibits no symptoms of low pressure that I find common in cars that actually have low oil pressure. But I just don't know how to double-check the reading I'm getting.

Jess

 

You'd have to install an independant guage to verify the actual pressure. This is not easy as the the only place (that I know of) to attach a guage is where the existing pressure sender is....very difficult access.

You're right to be suspicious of the factory gauges.

I might add that low pressure at-idle-when-hot is normal for the V12s. If the pressure comes up when opening the throttle, you're probably OK

Cheers
DD

 

The oil pressure needle comes up slightly on startup and then doesn't move at all, up or down, until you shut the car off, and then it returns to 0.

If you had to assign percentages, what would you think is the likelihood of the sending unit going bad rather than the gauge itself? I used to own a couple of late-80s Mitsubishi Starions and those things eat oil pressure sending units like popcorn.

Jess

 

I am new to the Jag life but in the 35 years I have been doing cars, I have found the vast majority of the time it is the sending unit. I keep a mechanical gauge out of an old GMC semi with a foot long piece of high pressure line on it & a couple of different adapters for most applications, that way I can know for sure.

 

50-50 :-)

My experience is they're both known trouble areas. Removing the cluster to clean the circuit board contacts and connector tabs (and add a redundant ground wire) is standard procedure on old XJSs so, IMHO, you might as well start there. Costs nothing and more often than not this makes the gauges pop back to life.

Cheers
DD