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Old 21-07-2016, 02:35   #1
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High oil pressure reading - Universal M3-20B

I have a 2003 Universal M3-20B on an Ericson 30 that I recently purchased.

Last time out, noticed that the oil pressure readings are 85-90 psi and don't fall as the engine warms. Water temp is fine and engine runs great. Based on reading, I tried to access the pressure relief valve at the filter. Changed the oil, removed the filter. Can't figure out how to remove the valve for service but the ball moves freely.

Replaced the filter and restarted. No real change.

With the engine completely cold and not yet started, the oil pressure reading is 35 psi before I even crank the engine (meter reads 0 with the ignition key off). After starting, the pressure rises up to ~85 and stays there. The pressure before even turning the oil pump doesn't make sense to me. Starting to think that the problem is with the pressure sensor.

Anyone ever experienced this? Any suggested solutions? I am trying to figure out if it is safe to run the engine.

Thanks for your advice.


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Old 21-07-2016, 04:34   #2
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Re: High oil pressure reading - Universal M3-20B

35 psi with power to the gauge but without the engine running is a sure sign of either a failed gauge/sender or an incomparable gauge/sender combo.

I wouldn't sweat it, just know that your normal operating pressure is 85, and if it drops to 35 or near 35 you've lost oil pressure.

Most cars on the road today have idiot lights and make more hours per year than the vast majority of diesels installed in pleasure craft, so absolute knowledge of pressure isn't a requirement for continued operation.

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Old 21-07-2016, 04:47   #3
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Re: High oil pressure reading - Universal M3-20B

Just buy and use a 'universal mechanical oil pressure gauge' to check the true oil pressure $27 is a small price for the reassurance.

Engine Oil Pressure Test Kit

"Remember, experience only means that you screw-up less often."
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Old 21-07-2016, 05:12   #4
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Re: High oil pressure reading - Universal M3-20B

Disconnect the wire from the oil pressure sender, then turn on the ignition.
With the wire not touching anything, the gage should read 0 psi. With the wire grounded to the block, the gage should read maximum scale. If so, the gage and wiring is good and the sender is faulty and should be replaced. If it's a two wire isolated ground sender, the same check can be made by jumping between the two wires.
Make sure the ohms range of the new sender matches that of the gage.

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