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oil pressure issue


91stranger

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started my truck this morning, weather was about 30-35 degrees but no frost on ground. oil pressure was low, like barely raises when starting the truck. truck started, idled, drove just fine. about 5 minutes of driving down the road it jumped up to normal and stayed normal. now I've seen a lot of issues with these sensors on these. Could it be something simple like a bad sensor? is there a way to test this without replacing a bunch of parts? I am a decent mechanic and can take on most issues but this is the only vehicle I have to drive and I work full time. so I cant be without my truck. Anyone know where this is located? I replaced a knock sensor on my 1991 ranger a long time ago. not sure if this would be in a similar area. my truck is a 1999 3.0 2wd, auto trans. Thanks for the help.
 


RonD

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Ford switched to oil pressure switches in late 1980's
The oil gauge is just on or off there is no movement by "pressure"

The switch is open when oil pressure is under 5psi, 0 on gauge
Switch is closed when oil pressure is above 5psi, gauge at "normal", depends on what resistor they used in your year.
So at 10psi or 30psi gauge stays in the same place, on or off

On the 3.0l the oil switch is on the passenger side of engine, back behind the head on the block.

Your oil gauge change could have been electrical issue, this is why you may see gauge rise with RPMs, if alternators voltage regulator isn't working well the voltage in system goes up with RPMs, so oil gauge needle would also go up, it is similar to volt meter in that respect.

But it could also be the switch is having internal resistance issue, it is the Ground for the gauge, when closed, so if the switch or its wire gets extra resistance then oil gauge needle would be lower.
 

91stranger

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Whats round on the sides and hi in the middle-OHIO
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4.2 straight six powered by gremlins, goblins and mudbloods.
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Automatic
2WD / 4WD
4WD
The oil gauge didn't move with the RPMs. It was low when I first started the truck. When I shut off the truck, I could see the needle drop a little like it did show a different reading other than on and off. I just didn't know if maybe the cold weather affected this. I was wrong on temperature. it was really about 20 degrees this morning.
 

Rearanger

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The only way to check oil pressure is with mechanical gauge.

I installed an AutoMeter electric gauge shortly after buying the truck. It shows variations in oil pressure. You'll find the access is not the best but I Tee'd off the stock on/off sender so I get both the stock fake needle and my real pressure gauge. Used a pillar gauge mount from HERE

THIS site has small digital electric oil gauges that may be better to mount on the dash.
 

RonD

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The oil gauge didn't move with the RPMs. It was low when I first started the truck. When I shut off the truck, I could see the needle drop a little like it did show a different reading other than on and off. I just didn't know if maybe the cold weather affected this. I was wrong on temperature. it was really about 20 degrees this morning.
If it moved up, even a little after start up and you didn't hear lifters "ticking" then your oil pressure was fine.

When key is on, engine off, oil needle should be on "0" pressure
After startup needle should move up, how far is moves is not really important from an operational standpoint.
It is in essence an Oil Light, on or off

If you are used to it being at a certain place on the gauge then replace sender/switch on the engine, not uncommon for these to need replacing.

Cold oil is very thick, and oil sender can get clogged up.
 

pjtoledo

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my 2000 with a 3.0 has had the flakey oil gauge for over 10 years. stays low and jumps up to normal a few miles down the road. sometimes its borderline and switches low-normal and back several times a second.
the fix is a clockwise rotation of that knob on the dash marked "volume" :icon_thumby:
 

91stranger

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Whats round on the sides and hi in the middle-OHIO
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2003
Make / Model
Gets Mo Chicks
Engine Size
4.2 straight six powered by gremlins, goblins and mudbloods.
Transmission
Automatic
2WD / 4WD
4WD
Seems like it only happens on really cold mornings. Also found that if I give the motor a good rev then the gauge jumps right to the middle where it normally is. Probably just think cold oil on a cold start up. Never had one this sensitive. Been waiting on an RV to get off our lift to be able to get a really good at it and make sure everything is what it should be. Its only got 106,000 miles so its still a young truck when compared to other vehicles I've had.
 

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