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To those with Oil Guage flicker...


KYEdge

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I have had trouble with this every since I bought my truck. I have had the gauge replaced. I even had a bad alternator and thought that might be the problem, after 4 alternators (it took that many to get a good one... Autozone remans are crap, I finally got a new one from my mechanic when I had the cam sensor replaced) I decided that wasn't the cause. After over two years of research I have narrowed it down to a bad ground.

With my truck it only happens after it is really hot. A long trip when it is cold out (1+ hour) will cause the gauge to flicker like crazy until I shut the engine off and let it cool down for a while. If I just shut it down for a few minutes it will be fine until another few minutes of driving and then it starts again. A short trip while it is really hot out (say 20-30 minutes at 90+°) will cause the same oil pressure gauge flicker. When it happens the truck does feel to run a bit more rough than usual at idle, but smooths out and runs like a top once the RPMs get above idle.

I know there are others out there with this exact same problem, because a Google search turns up results on a few other forums with the exact same symptoms.

The final nail in the coffin though was when I noticed I was getting some intermittent noise on certain FM radio stations. So I flipped over to AM and lo and behold I am also getting noise on AM stations that seems to correspond to the engine RPMs. The FM noise is very rare really, and when it happens all I have to do is shut off the truck and restart and it tends to go away, but that alone tells me that it isn't environmental interference.

So it has to be a bad ground somewhere. The next step is trying to figure out exactly which ground it is.
 


Buba Ganushe

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If you can figure this out many of us would appriciate it. i asked this same question not to long ago and was told... "probably your sending unit. However- on these trucks the sending unit is just on/off and a resistor is put into the circuit so the gauge reads in the middle when you have a minimum pressure (I think it's only 8 psi). The sending unit is behind the right side head, and a bit of a pain to get to. If you are going to replace it, might be a good time to install a real gauge. If you are running 5-20 oil, you might want to try 5-30, the higher weight will give a bit more pressure when hot, and 5-30 was the recommended weight until about 2002 (I think), when Ford switched to 5-20 to get a tad more fuel mileage for the CAFE standards. I have been running 10-40 inmine for years with no problems, but I always let the thing warm up a bit before I go blasting down the road. Also, these engines are noted for the cam position sensor gear going. The cam position sensor asembly also runs the oil pump. many people replace it at about 90-100K just as preventative maintainence.
Tom-I do not believe the oil pressure sensor is hooked into the CEL."
 

Original_Ranger84

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Ok well the first thing you should do even though Buba Ganushe said it didn't help would be to replace the sensor (usually its only the sensor if your not getting oil pressure at start up but It could be a faulty sensor.) Cause a resistor it is... the hotter it gets the more resistance it will create and when you let it cool off the resistance will go away.... Also when you replace it check the wires back up to where they disappear somewhere and make sure they aren't rubbed through or resting on anything that gets really hot. If that doesn't solve it you may have another problem from the computer or something cause its not a complicated system, there is the sensor, wiring and the gauge... I'm leaning towards the wiring but replace the sensor as a caution (its not that expensive.)

As for the whining in your stereo... I hate to say it but its your alternator... The alternator has a built in condenser that prevents static from getting to your stereo and if not rebuilt properly or its old it can start to let static from the high power get through. Also is your stereo a custom stereo? and did you run any wires out to the engine bay? So you should just buck up and get a brand new alternator probably cause if you went through 4 rebuilds they obviously don't know what they are doing, I would get a napa rebuild or new one. They are more expensive but I have never had a part go bad or not fit right from them.

Or you could always take the alternator to a specialist and have it tested and rebuilt or just the one part replaced.
 

backroad101

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Mine did this only once, and was after getting off the highway after driving for about an hour. Never did it again.

Not sure if it was related, but my check engine light did come on I had to replace the IAC (symptoms present before I took the trip). Not sure if it was related since I have not taken that long of a trip since
 
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KYEdge

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Ok well the first thing you should do even though Buba Ganushe said it didn't help would be to replace the sensor (usually its only the sensor if your not getting oil pressure at start up but It could be a faulty sensor.) Cause a resistor it is... the hotter it gets the more resistance it will create and when you let it cool off the resistance will go away.... Also when you replace it check the wires back up to where they disappear somewhere and make sure they aren't rubbed through or resting on anything that gets really hot. If that doesn't solve it you may have another problem from the computer or something cause its not a complicated system, there is the sensor, wiring and the gauge... I'm leaning towards the wiring but replace the sensor as a caution (its not that expensive.)

As for the whining in your stereo... I hate to say it but its your alternator... The alternator has a built in condenser that prevents static from getting to your stereo and if not rebuilt properly or its old it can start to let static from the high power get through. Also is your stereo a custom stereo? and did you run any wires out to the engine bay? So you should just buck up and get a brand new alternator probably cause if you went through 4 rebuilds they obviously don't know what they are doing, I would get a napa rebuild or new one. They are more expensive but I have never had a part go bad or not fit right from them.

Or you could always take the alternator to a specialist and have it tested and rebuilt or just the one part replaced.
Already replaced the sending unit. It is most definitely a bad ground, I confirmed it tonight. I got it hot enough to start flickering and then had my dad help me out. He blipped the throttle and watched the gauge. I hooked my DMM between the positive post and the ground strap. I could call out every time the gauge flickered because I had a 3+ drop in voltage.

Since it only happens when the truck is hot I'm thinking the bad wire has to be somewhere near the exhaust, probably on the bottom of the engine.

I'm going to crawl up under it tomorrow and look around.

Also, I ditched the remans and bought a new alternator from Gipe (a local Federated place). I won't buy anything remaned from Autozone ever again.
 

Original_Ranger84

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Already replaced the sending unit. It is most definitely a bad ground, I confirmed it tonight. I got it hot enough to start flickering and then had my dad help me out. He blipped the throttle and watched the gauge. I hooked my DMM between the positive post and the ground strap. I could call out every time the gauge flickered because I had a 3+ drop in voltage.

Since it only happens when the truck is hot I'm thinking the bad wire has to be somewhere near the exhaust, probably on the bottom of the engine.

I'm going to crawl up under it tomorrow and look around.

Also, I ditched the remans and bought a new alternator from Gipe (a local Federated place). I won't buy anything remaned from Autozone ever again.
Ok well atleast you got a new unit that hopefully won't go bad any time soon. Yep look at the grounds and power wire.

Did the new alternator fix the buzz?
 

KYEdge

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Nope. Now admittedly I think this new alternator has a bad voltage regulator, but that is a whole different problem.

I have looked and looked but cannot find the main body to chassis ground. All of the body grounds look good, and they all Ohm out in the normal range. So it is one somewhere I can't see, and I suspect it is probably a frame ground but I can only find one back near the fuel tank.
 

fourwheelford

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I have a ground on the frame below the passanger side door, there are quite a few of them though.
 

Original_Ranger84

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Yeah just look around the frame. and if you can't find more that could be part of it.... I don't know.....
 

McCormack

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Ford offers a dealer fix for Ranger radio whine, so if you can't find the problem then the dealer fix might be an option.
 

oldfordman

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Why not hook up an extra ground or two? Go from a bolt on the engine to the body, then continue down to the frame. Would be a lot quicker than tracking down each ground strap.
 

KYEdge

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Why not hook up an extra ground or two? Go from a bolt on the engine to the body, then continue down to the frame. Would be a lot quicker than tracking down each ground strap.
That is actually a pretty good idea.
 

bcost882

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i have had the flicker after a drive down the highway and back to idle in 100+ vegas weather, and then when it was cold in the winter (of course i mean vegas cold not maine cold) the oil preassure would bounce up once bounce down and stay down till the engine started to warm up.
 

AngryIron

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Mine would only flicker after a high RPM run..... Then the motor seized up my fix is to put in a mechanical gage along with a new motor. Are you guys sure it is electrical and not actually a low oil pressure problem. You know the gage will not drop to Zero unless the pressure goes below 9 psi? The gage is not an actual gage it is more of an idiot light setup either you have pressure or you don't. I have seen a fix to place a jumper over the resistor and replace the sending unit that will give you a low medium and high reading but still not accurate enough for me.
 
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KYEdge

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Well, it is possible that I do have an actual oil pressure problem, but I do know that I have a bad ground; I saw the voltage drop when I tested for it.
 

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