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Old 08-31-2010, 07:04 AM   #1
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Oil gauge

The oil pressure on my Lehman 120 usually reads arounf 40 PSI. But once in a while I'll take a look at the gauge and the needle is at the very end of the dial (above 80 PSI). It doesn't make sense to me that the oil pressure would rise that much and the engine would still run without a problem for hours. I suspect an electrical problem, or maybe a problem with the sender unit?
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Old 08-31-2010, 07:27 AM   #2
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RE: Oil gauge

Fotoman, the only time my gauge rocked over to the high end, was when a mechanic had knocked against the connection on the sender and it was barely making contact. Pushing it back on properly set it right.
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Old 08-31-2010, 08:28 AM   #3
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RE: Oil gauge

Thanks Peter, that's what makes sense to me. I'll take a look tonight at the sender.
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Old 08-31-2010, 10:11 AM   #4
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RE: Oil gauge

Sometimes the loss of a good ground will do similar nonsense.
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Old 09-03-2010, 07:27 AM   #5
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RE: Oil gauge

Ok, that's weird, the gauge now reads 40 psi... even when the engine is not running and the key is not in the ignition! So definitely an electrical problem.

I can't locate the oil pressure sender. Where is it?
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Old 09-03-2010, 07:50 AM   #6
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RE: Oil gauge

Quote:
Fotoman wrote:

Ok, that's weird, the gauge now reads 40 psi... even when the engine is not running and the key is not in the ignition! So definitely an electrical problem.

I can't locate the oil pressure sender. Where is it?
Disconnect the gauge with out turning the key or anything.* If it stays where it is you answered you own question.* If it changes then put the wire back on and see if it goes up again.

With nothing on it sure doesn't sound like the sender.

*
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Old 09-03-2010, 08:25 AM   #7
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RE: Oil gauge

Our gauges often stay in the same position they are in when the key is turned off. When we turn the key on without starting the engine, they drop to 0. Don't ask me why, but other than this, they seem to function fine. Chuck
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Old 09-03-2010, 10:53 AM   #8
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Oil gauge

Chuck, it is a function of how the guage is powered. What is the saying...."DC lies....AC dies"...or maybe the other way around???? Anyway, one of them, when you remove power, it dies...meaning it goes to 0. The other, it lies....meaning it stays where it was last.

-- Edited by Baker on Saturday 4th of September 2010 11:24:28 PM
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Old 09-03-2010, 12:00 PM   #9
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RE: Oil gauge

HMMM, my gauges are all DC powered. Chuck
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Old 09-04-2010, 12:46 PM   #10
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RE: Oil gauge

With many makes of engine type gauges the manufacturers include a "damping" feature. The main purpose of this feature is to stop vibration and very small "pulses" from registering on the gauge. Depending on how this damping feature is enabled, the gauge may not return to zero when the power is removed simply because there is no electrical current present in the gauge to overcome the damping feature.
On Penta I have all Stewart Warner electric gauges and the all stay relatively close to where they were last registering when the power is removed. As soon as the key is turned "on" they all drop to zero and then start registering whatever the senders tell them to once the engine starts.
Hope this helps you troubleshoot your problem.
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Old 09-04-2010, 11:23 PM   #11
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RE: Oil gauge

Folks, I think you need to refer to my post. DC Lies........
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Old 09-05-2010, 07:02 AM   #12
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RE: Oil gauge

My favorite co Murphy actually makes an oil level gauge.

Instalation needs the pan dropped , but for a engine rebuild or swop , it could make sense to know the volume in the pan, rather than simply wait for the alarm to scream NO OIL PRESSURE.
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