1989 XJS:

The oil light on dash stays on after engine has started. Oil pressure GAUGE moves after starting, moves to about 25 lbs and then drops slowly which seems to indicate regular oil pressure.

So, I replaced the oil pressure idiot light sensor-and the light is still on!

What next?

 

What does the light do with the sender disconnected? Try it with the sender wire grounded also.

 

As Baxtor said.

If the light is ON with the wire unplugged from the sensor, that wire is grounded in the loom somewhere.

The gauge sender is notoriously unreliable, so for show it is mainly.

Just to be sure, attach a master mechanical gauge to the hole where the idiot switch should be and take some real time readings.

Mine was 90psi cold at 1000rpm. 45psi,hot, at 1000rpm. The dash gauge was close for the cold side, but around 15psi for the hot side.

 

So I unplugged wire and it stayed lit. Then I plugged wire back in and is now working properly.

The 1989 equivalent of restarting your computer...

 

That would indicate a break in wire to earth, probably in the area of disturbance.

 

HAHAHA. I luv the sense of humour.

You, SIR, will go a long way in the world of the V12, trust me.

Doug calls it the "Fiddle Factor" and I like that a lot.