Oil pressure gauge accuracy

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Joined: 25 Jun 2024, 11:27

Oil pressure gauge accuracy

Unread post by Ringsy »

I have recently been through a process which I think others may be able to relate to.

The oil pressure displayed on the gauge of my Fulvia 3 (1.3) wasn’t very good, although any rattles to suggest a serious issue were absent.

At tickover over it was barely registering and at 3,000 RPM with the oil at working temperature, it was reluctant to get to the halfway mark (35) on the gauge.

I had the engine rebored due to poor compression and lipping on the bores and the bearings seemed fine with virtually no wear on the crankshaft. The bearings were of course replaced anyway.

There was only a slight improvement to the oil pressure which was a little worrying, although I did suspect a faulty or incorrect sensor. I couldn’t see any markings on it to indicate its specification.

I needed to get to the bottom of it for my own peace of mind, so I bought an inexpensive oil pressure testing kit on Amazon. I was able to remove the oil temperature plug from the oil filter mounting base (extremely tightly done up - use a good quality allen key with a ratchet wrench) and attach the oil pressure testing unit pipe to it using the correct adapter from the kit and a right-angle adapter also supplied with the kit. Not only did this enable a simultaneous pressure reading to directly compare it with the car’s own gauge, but it wasn’t necessary to remove the oil filter to access anything. I did remove the air filter box to get better access.

The results were remarkable. The test gauge showed excellent oil pressure throughout the range whilst the car’s instrument showed under half! Clearly the sensor unit was either faulty or the wrong specification. The car’s gauge is unlikely to be wrong as it’s essentially a voltmeter and there’s not much to go wrong with one in theory.

Anyway, I hope this post will help people who are suffering from apparent low oil pressure. The kit cost £28, was easy to link up and not a drop of oil was spilled! Thanks also to Pieces Fulvia who confirmed that I could use the temperature sensor port to do the job.

The kit was:

FreeTec Engine Cylinder Oil Pressure Diagnostic Tester Tool Set for VW BMW Opel Ford Fiat

I guess there are many kits that do exactly the same, but this one with the 90 degree adapter fitted in the space - just.
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