Oil pressure question

I fitted a digital gauge to my 200tdi converted series 2. It was one I had bought a couple of months ago for a project car that in the end was far too costly. The make of the gauge is race-x who I'd never heard of before.

Fitted it all to the Tdi via a t-piece and started to it up to look for leaks and was oil tight.

The cold idle on initial start up is 61psi and at about 2000rpm 78psi which seems quite high. The gauge did start from zero also.
I got it up to normal coolant temperature but not oil temperature and this dropped to 45psi at idle. The engine is a 200,000 mile Tdi which has brand new filters and oil of the correct spec.

Another question is should a gauge pick up oil pressure when the engine is off? Will there still be pressure within the engine immediately when switched off as with the engine switched off and ignition on the gauge was reading 32psi.

The engine doesn't breathe heavily so if this is considered high oil pressure I can't see anything being blocked. The Cyclone breather is vented to atmosphere and doesn't cover the engine in oil.

With an engine at running temperature residual oil pressure will drop to zero pretty well as soon as the crank stops turning. If you are getting 32psi with the engine stopped then you have some sort of indication problem, probably an earth related issue as the engine block earth and gauge earth need to be identical for accurate readings. Just a thought, have you tried disconnecting the sender and see what the gauge does with the ignition on?

Kwakerman said:

With an engine at running temperature residual oil pressure will drop to zero pretty well as soon as the crank stops turning. If you are getting 32psi with the engine stopped then you have some sort of indication problem, probably an earth related issue as the engine block earth and gauge earth need to be identical for accurate readings. Just a thought, have you tried disconnecting the sender and see what the gauge does with the ignition on?

Click to expand...

Gauge goes to zero when sender is disconnected. However I've played about with it and it's zeroing after building up pressure and switching the engine off. So faulty earth I'm assuming.
Pressure readings are staying the same at 60psi when cold and moving into the lower 40's when starting to get to normal operating temperature. Do these sound okay?

Probably indicating a bit on the high side, the best way to confirm would be to put a mechanical gauge where the oil pressure switch goes and do a comparison.

Bin it and get a proper mechanical gauge..................... £30.00 or so - done job