When I start my Eunos the oil pressure goes fully right and apparently off the clock. The indicated overpressure stays until the car is warmed up and then gently comes down until it sits about 2/3rds right, I suspect still too high. I do not know where to start. Any ideas as to either the cause of the problem or how to begin the diagnostic process.
Thanks for your thoughts
It could be the oil pressure relief valve in the oil pump is sticky or the pressure sensor may be faulty what year is your car as prior to around 94 there was a change in the oil pressure guage sensor.
Mine goes to top of scale when cold and once warm runs at just over the 3, on tick over it drops to just above the 2. been like that for 4 years.
I’d get the oil pressure checked with a calibrated workshop oil pressure gauge before believing what the dash gauge is telling you.
Thanks for your replies, it gives me some ideas on how to go forward
My MK1 does the same thing and I was told that it’s just the viscosity of the oil which takes a while before it reaches it’s normal operating temperature. Like Mal Jones, mines been like that for some time and there are no other signs of there being a problem, but have it checked I’d be interested to see what you discover.
Will do
Hi - My 1990 Eunos (80K Miles) has similar high “Indicated” Oil Pressure. It goes to 4 plus when starting before dropping to around 3 plus when cruising. If I push the revs up above 4,500 it will hold at 4. Have had the car for 5 years and its always been the same. It burns no oil between annual changes (3 to 5K miles) and runs on fully synthetic.o would also be interested
Have never had it checked so would also be interested in hearing how you get on.
Rod
It’s my understanding that early MX5 oil ‘pressure’ gauges are only really ‘on’ or ‘off’ switches.
The oil goes through the system and turns the switch on, the gauge moves. Sometimes all the way to the right.
When electrical components within the gauge or dial warm up, the resistance in the circuit reduces an the dashboard gauge drops.
Are you sure this is not the case here?
Get yourself a real pressure gauge and check it for real
I think it’s the other way around and the early MK1’s had the numbered oil pressure meters. Mines a 92 and certainly seems to support this view.
That’s right. The early cars have a real oil pressure gauge and a real pressure sensor screwed into the block. The change came during 1995 and later cars got a dummy gauge and a simple open/closed pressure switch on the engine.
It’s normal for (real) oil pressure to indicate around 90psi (or 6 kg/cm² for Roadsters) at startup, but it shouldn’t go off the scale. There’s a spring loaded pressure relief valve in the oil pump which should open if the pressure gets too high and dump some oil back into the sump rather than forcing it all though the filter and the engine. From memory that starts to open nominally around 65psi. If it jams shut the pressure could go too high with cold, thick oil at high rpm. If it jams open the pressure could drop too low when warmed through.