Low Oil Pressure Reading

[TourEnvy]

I have a Autometer Electrical Oil Pressure Gauge. It has been noticably low. At idle, warm it use to be a 12.5 psi. it is taped into the head (normal from what i read). Now at idle it fluctuates but drops off to the 0 reading sometimes. The needle still moves and at 3k rpm it doest want to get above 15-20 psi. I find i get a more normal readings when the car is cool.

We had record breaking July with extreme high average of 106* for the Month, some days 115*. I have 1k of city driving on the car in only a months time. I have checked the oil and it is good. 5w30 Mobil 5000 dino.

I was wondering what the issue could be? Could the heat cause premature break down?

I thought it may be the sending unit but while researching I have only come across complete failures and really bouncy needles.

I have bought stuff for an oil change, as i thought it might help. However I dont feel that doing oil changes every 1k is fun.

 

[striker2]

you drove 1,000,000 miles in 1 month and on the same oil? yikes! :laugh:


anyways, the first thing i would check would be to make sure there isnt anything blocking the sending unit. I would also pull the pan and make sure there isnt anything blocking the oil pickup.

 

[gmorrell]

Before you start tearing things apart, you need to sanity check your data.

What style/model Autometer gauge?

Does it use a resistive pressure sender?

Or a voltage-out pressure sensor?

The resistive senders can go bad due to vibration, especially if mounted directly on the engine. They can also read erratically if they have a poor case ground, as they rely on the fitting thread into the block to get this ground. Try temporarily connecting the sender case to the battery negative terminal with a length of wire, see if anything changes.

The voltage-out pressure sensors typically require a 5V power supply from the gauge internals to work properly, and I've seen failures in the gauge 5V supply to the sensor.

If this were me, I'd borrow or buy a good old fashioned mechanical pressure gauge and screw it into the head oil port as a sanity check. If the engine oil pressure is really getting as low as you said, you should be having other nasty issues like tappet noise and rod knock.

Are you seeing the oil pressure light on the dash come on?

To my knowledge, all of Autometer's electric/electronic oil pressure gauges are 100psi max, and I've seen my CSVT oil pressure go well beyond 125psi on a cold day, which is why I used a Ultra-Lite 4232 150 psi mechanical gauge. The cold start over-pressure may eventually damage a resistive sender.

 

[TourEnvy]

With the needle now past 0 psi and the car is running I figure its a gauge issue. Last night I swapped out the 2422 sendor for a new one and had the same issues. Come to find out the sendor needs to be grounded itself which I didnt know. I had been moving hings around in the engine bay and apparently where the sendor was wedged/tie wraped wworked for 3 years but now Im having some issues.

Like you said - bad ground and Im determining that right now with a sperate ground wire.


I had bought a mechanical gauge but I went around everywhere trying to find a fitting to pair with my braided line but wasnt avaliable. I got luck to find a sensor in stock... but as mentioned didnt work.

The engine is running like a top w/ plenty of oil. On to the ground!

 

[TourEnvy]

Well I was able to fab up a pretty nice bracket IMO at work. Everything seems to work at it did before. I have such the dumbest things happen to me (because of me).

 

[gmorrell]

Glad you fixed it. Ockham's razor: The simplest explanation is usually the correct one.

Aren't you glad you didn't pull the oil pan? :laugh:

 

[TourEnvy]

Yeah, Im not sure if I would have but It would have been somewhere on the list down the line. Funny thing is I was on the phone with Autometer before I checked the thread and said the same things. You can also check the sending unit by blowing air softly into it while still grounded.

I dont ever recall seeing information on grounding the sending unit when remote mounting. Its assumed when you mount it to the block that its grounded. However once you add in the braided line, adapters and teflon, the ground might not be as good anymore. He also mention to take some of the zinc coating off the sending unit if using a strap method.

 

[striker2]

I didnt realize you had the sender remote mounted or checking the ground definitely would have been my first suggestion. I had the same problem when i first installed my oil pressure gauge as well.