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Apparent loss of oil pressure '99 3.0

rangertodd

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Looking to get some advice here. I'm not sure which way to handle this oil pressure issue I'm having. The oil pressure of my '99 Ranger 3.0 dropped to zero while I was driving. My first thought was cam position sensor, as it is pretty infamous for breaking. However I never had any whining sounds coming from the back of the engine, and I was able to drive the truck home about 3 miles (I had no choice) without any weird noises or other problems.
That led to my second thought that it was just the oil pressure sensor on the block that went bad. So I replaced the sensor and still no oil pressure. Now I'm stuck between either chasing the problem up the line to the oil gauge, or focus back on the cam position sensor.
Any idea which way I should go? I have a bad sciatica, so I can't do too much work on my truck at a time. Thanks.
 


Rearanger

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I was able to drive the truck home about 3 miles (I had no choice) without any weird noises or other problems.
Doesn't sound serious. See if you can get a free loaner oil pressure tester from local parts store. You'd plug that into the sender connection to get a manual reading on actual oil pressure. Sounds like your gauge.

Stupid question - did you check your oil level?
 

JP02XLT

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Or the oil sending unit

JP02XLT
 

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"So I replaced the sensor and still no oil pressure. "

Unless the new sensor was bad.
 

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Ground the wire for the pressure switch. If the gauge and wire are ok the gauge will peg.
 

Rearanger

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Ground the wire for the pressure switch. If the gauge and wire are ok the gauge will peg.
I read that's not safe for the gauge without a resister???
 

rangertodd

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Thanks for the advice thus far. I did check to make sure that the oil level was good. The thought did cross my mind that the new sensor could be junk, but it was such torture getting to it the first time with my messed up back that I wanted to explore all the options before doing anything else.
I do have another question. If I simply took out the oil sensor (sending unit) and started the motor, would oil spraying out of the open hole positively indicate that the oil pump was working, or would it just be a really bad idea?
 

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or would it just be a really bad idea?
That would only tell you the pump can provide flow not pressure. Not a good test. If you really had no oil pressure and drove 3+ miles the engine would have seized.
 

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It may not have seized. I drove 7 miles with no oil pressure once and the engine didn't seize. It wiped out the rings and she wouldn't fire. That was after 100 mile trip with low pressure, and the thrust bearing spun partway home.
 

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It may not have seized.
On another note a friends Mustang 289 blew oil out a just failed oil pressure switch, unnoticed to us while idling. It only ran about 30 seconds before it was turned off as we were looking for air bubbles in AF, then found oil on the floor.

It did not seize while running but it sure was seized when we tried to turn crank pulley by hand - locked solid. Even the lifters didn't make noise.
 

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"So I replaced the sensor and still no oil pressure. "

Unless the new sensor was bad.
Just went through 3 (run of the mill auto parts store brand) sensors working on a friends Ranger, 1st unit, no signal at all, 2nd was erratic, high to low oil pressure reading, 3rd one was a winner.

JP02XLT
 

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Thanks for the responses, guys. I guess I'll just bite the bullet and buy an oil pressure testing gauge ans try that. At least it will give me a precise indication of the oil pressure, and let me know if the pump is dead, weak, or fine.
 

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If you thought you wanted to add a mechanical gauge then just buy that and use as your test gauge initially, then install it permanently to always have pressure indicator. You can install it in tandem with standard idiot factory gauge.
 

rangertodd

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If you thought you wanted to add a mechanical gauge then just buy that and use as your test gauge initially, then install it permanently to always have pressure indicator. You can install it in tandem with standard idiot factory gauge.
It's funny that you say that, Rearanger. That's exactly what I did yesterday. Autozone doesn't loan out oil pressure testers and they're like $65 to buy. But a mechanical oil pressure gauge is only $15!
 

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The oil pressure gauge confirmed zero oil pressure, so I pulled the cam position sensor assembly. The top end looked perfect--no damage to the sensor or the tab that spins around inside it. The bottom half though was another story. The gears were worn thin and several of them side by side were broken off.
I replaced it and got the oil pressure back. 50 PSI at first, then it dropped to 25 after about 10 minutes. Is this normal? I never noticed any pressure drop with the idiot light gauge (obviously).
 

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