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Old 12-04-2014
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I am: Bryan West
Join Date: Oct 2014
Location: Sheffield, Oh
Vehicle: 2001 Ford Ranger
Drive Type: 4x4
Engine: 4.0
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oil pressure guage is crazy!

So for some reason, at idle my oil pressure gauge drops all the way down. hit the gas and it jumps right up..ls this just a faulty gauge or do i really have an issue. Not sure if i should be worried or not. help friends!
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Old 12-04-2014
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I am: Ron Dean
Join Date: Jan 2014
Location: Vancouver, BC
Vehicle: 1994 Ford Ranger
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Ford uses an oil pressure switch for the gauge.
Below 6psi pressure the switch is open so gauge reads 0
Above 6psi pressure switch is closed so gauge reads about 1/2

If could be the switch is going bad.
Or if you hear valve train tapping noises at idle then you really do have low oil pressure, valve train will usually start to make noise when oil pressure gets down to about 4psi.

Oil pressure comes from TOO MUCH oil.
Oil pump pushes oil thru the filter and into the main oil passage, where oil pressure switch is, because the bearings and passages are small they don't allow all the oil to flow out.
This builds up a back pressure in the main passage which we see/read as oil pressure.

As bearings wear they pass more oil, larger gap, so high mile engines have lower oil pressure in general.
People often run a thicker oil in high milers to keep pressure above 6psi.
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Old 12-05-2014
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I am: Kevin
Join Date: May 2014
Location: Lake Mary, Florida
Vehicle: 2000 Ford Ranger
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When my oil pressure "switch" went bad, it would simply not register any oil pressure at all; the cluster gauge was resting as if the engine was shut off. After about one minute, it shot up to its center position, indicating I had "oil pressure", as RonD has described.

In your case however, it sounds as if you may have an issue with correct engine oil pressure. You did not mention the year of your Ranger, which is important, as the earlier Rangers used a true oil pressure gauge setup, the oil gauge needle would fluctuate a bit as the engine RPM's increased/decreased. The newer Rangers only show "pressure", again as RonD has described.

Only way for you to test is first by noise, as suggested. If you hear some valvetrain clatter at idle or low RPM's, then it's most likely you have low oil pressure; not enough oil is reaching the valve train at low RPM/idle. This is a condition when the main and rod bearings become worn, allowing more oil to flow past, and therefore reducing oil pressure. I'll also assume you have oil in the pan, enough to be at least on the "add" mark of the dipstick.

If you are not hearing valve train clatter at low RPMs/idle, you can replace the oil pressure sender (or switch in newer year Rangers) and see if that corrects the gauge issue, or connect an oil pressure gauge to the hole that the factory sender/switch is in, and see first hand with this temporary setup if you are getting good oil pressure. This would be the best test, to provide piece of mind that the oil pressure is alright.
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