Oil pressure gauge drops (but pressure ok)

[ybakos]

Hi drivers,
I've got a 1991 Montero LS with a finicky oil pressure gauge. When I turn the key and start her up, the gauge displays a decent pressure. But then it quickly drops and remains low when idling/driving. The oil pressure is ok, and I think the previous owner might have used a cheap/incompatible sensor.

Any suggestions on how to troubleshoot, what to take apart and/or replace? Thanks for the tips.

[arrow]

I think the previous owner might have used a cheap/incompatible sensor.

That's be a good place to start if you think that's the case. They're not that expensive from when we replaced one.

[nj swb]

Hi drivers,
I've got a 1991 Montero LS with a finicky oil pressure gauge. When I turn the key and start her up, the gauge displays a decent pressure. But then it quickly drops and remains low when idling/driving. The oil pressure is ok, and I think the previous owner might have used a cheap/incompatible sensor.

Any suggestions on how to troubleshoot, what to take apart and/or replace? Thanks for the tips.

Hi ybakos, welcome to the forum.

I agree that it sounds like pressure sensor, but old factory sensors can do something like this - show good pressure when the oil is cold or engine revs are "normal", but show low pressure at idle when warm.

Buy a quality replacement sender, and see where that leaves you.

Good luck.

[ybakos]

Thanks everyone. I'll see about getting a replacement sender and sensor. These are two different parts, yes?

[nj swb]

Thanks everyone. I'll see about getting a replacement sender and sensor. These are two different parts, yes?

No. Two different terms for the one part. The bit that screws into the block, senses the pressure and sends an electrical signal.

To me, the best bet is that this is your problem. Unfortunately, an aftermarket replacement isn't a 100% guarantee fix, because there's a small chance that a non-genuine replacement isn't the correct replacement.

If a replacement sensor / sender works as expected - happy days!

If it doesn't work, is it a different problem, or the wrong replacement? Being able to test with a known good replacement would be a huge help.

[TomW]

In all honesty the factory oil pressure gauge is pretty inaccurate, even with a new sensor it will be at best an approximation. You would be better served replacing the factory gauge with an aftermarket one. Its a pretty easy job to do and a big improvement over the factory gauge.

[ybakos]

Thanks everyone. I've found two different kinds of sensors, with drastic price difference, but I suspect that I'll have to buy the more expensive one (and I have my suspicions about why my current sender/gauge is behaving the way it does).

Some senders are for lights, others are for gauges. The ones for gauges are more expensive (I have found). And I think that the sender I have must be for a light, which makes sense:

Turn the key on, oil pressure gauge goes up to max. I think that a sender for a light would turn on the oil pressure light until the car starts, so it is sending a current to the gauge. Once I start the car, the sender "turns off" the light, which causes my gauge to drop to 0.

Am I on the right track here? Just wanted a sanity check before I buy a sender that is "for a gauge" rather than "for a light."

[TomW]

Yep, you are on the right track, the behaviour you describe sounds like a switch has been installed rather than a proportional sensor (assuming the gauge drops to 0 the moment the engine is started) The sensor should be a largish can type thing like this https://encrypted-tbn0.gstatic.com/i...jyfweU-JLbfy4z

[ybakos]

I replaced it with a proper type of sender and the gauge now works as it should. Thanks everyone for the insight.

I will say that the gauge does indeed report a much lower pressure when warm and idling, when compared to when it’s cold. It reads 60 psi when cool, and about 20 when warm and idling, but rises during revs. I know the gauge isn’t accurate in general, just sharing what I’m observing.