Truckster (Vic) replied:

Did you replace the oil pressure sender?

Mine on GQ moves from 0-4 on the gauge on the dash, but it stopped once, it was the sender, $90 new from Missan... Ouch!

I too have VDO sitting right infront of me, going in, with some others into a dash pod... I really need to get my finger out soon!

Nat replied:

Just a quick thought. I never rely on electronic gauges for major things i.e Water temp, & Oil pressure. No sender switch required only problem is once the oil feed line on the gauge had a fracture inside the car and sprayed a little bit of oil on my leg.

nugget replied:

David,

The oil pressure gauge in my GQ Patrol diesel does seem to behave erratically at times. One day it reads 400 kpa, and the next it sits at around 300 kpa. I'm hoping it's the sender and not something more sinister though. You say you are going to have a look at the relief valve, You may also wish to look at the regulator valve aswell (situated below the forward oil filter) making sure it's not sticking or the spring is weak or broken. You could always put a washer or two under the spring which will increase you oil pressure but it could just be hiding a larger problem, worn bearings etc.
Just a word of warning regarding mechanical oil pressure gauges. Make sure you route the plastic tubing away from any electrical wiring. I once had the misfortune of having an electrical short years ago and the wiring melted through the plastic tubing causing oil to leak behind the dash. luckily I noticed it when investigating the electrical problem otherwise it could have emptied the engine of oil. And yes it was a Landrover (series 11).