High Oil Pressure

udmsvt · Jul 29, 2013

I tried searching and was not finding many answers...

94 4.0 5-speed 4x4. After driving around, the oil pressure will make it just past the L of normal. If I park it for a few min, it will drop back to around the A. Truck seems to run ok otherwise and it just got a Mobil 1 5w30 oil change 1200 miles ago.

I've had several explorers and ranger before and never seen it get this high.

Should I be concerned? What should I look for?

RonD · Jul 29, 2013

A new oil pressure switch.
Ford gauges don't show real oil pressure, they use a switch.
They often go bad and cycle from low to middle, but also to full.

There could be a problem with the actual oil pressure, but 99% of the time the switch is the problem.

Google: Oil Pressure Sensor Install on a 4.0 Liter Ford Engine

Good video

Frank The Tank · Jul 29, 2013

I would put a mechanical gauge on there to be 100 percent sure also. However most ppl probably don't just keep a spare mechanical oil pressure gauge laying around for those situations...

udmsvt · Jul 29, 2013

Watched the video. It was useless. I did however find a diagram over on the explorer forum.

So assuming I spend 12 bucks on the part, it looks like all that will do is tell my analog dummy gauge to show a lower pressure, correct? Or does the switch actually do anything besides open and close to adjust the gauge?

budro · Jul 30, 2013

My understanding its just a variable resistor to ground.

RonD · Jul 30, 2013

It is just a switch, opens below 6psi, closes above 6psi.
The gauge has a 20ohm resistor so when switch grounds the gauge(closes) it should show about 50% of current battery voltage, and gauge will vary with voltage.
13.6v(running alternator) through 20ohm resistor gives 6.8v
This is also why the gauge seems to move with RPM, but it's not oil pressure moving it, it's alternator output.
So if charging system is working correctly then oil pressure is steady as a rock, lmao.

The '94 gauge can be converted to a "real" oil pressure gauge, although the gauge doesn't have PSI numbers, but it would go up and down based on oil pressure not battery voltage.
You need a PS60 sending unit, these are not switches.
You need to pull the instrument cluster and solder a jumper wire across the external 20 ohm resistor.
In '96 or '97 they switch to internal resistance for that gauge, and in '99, I think, they ran oil pressure reading from a module to the gauge, not directly from the switch, "digital"

udmsvt · Jul 31, 2013

So...I can basically ignore it assuming the truck runs fine?

High Oil Pressure

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