Help needed: oil pressure gauge pegs out
#1
Help needed: oil pressure gauge pegs out
This has been going on for several months and I'd like to do something about it since I'm getting concerned about the amount of miles I have on the engine. I tried searching for a relevant thread but didn't have much luck...
The vehicle is an 2001 F150 with a standard 4.6L (no mods at all.)
On start-up, the oil pressure gauge goes directly to high pressure and stays pegged up there. Sometimes, after driving a long while, the needle comes back down to the middle of the normal range and stays there. On shut-down, the needle goes down to its resting position.
There are no other symptoms that something is going wrong. Is it the gauge or the sensor or what? Our company's mechanic seemed to think that, as long as I don't blow out my filter or any seals, everything would be ok.
Any thoughts? I'd like to have a functioning gauge at least. I know that the stock gauge is a binary indication device, but I'd like for it to work.
The vehicle is an 2001 F150 with a standard 4.6L (no mods at all.)
On start-up, the oil pressure gauge goes directly to high pressure and stays pegged up there. Sometimes, after driving a long while, the needle comes back down to the middle of the normal range and stays there. On shut-down, the needle goes down to its resting position.
There are no other symptoms that something is going wrong. Is it the gauge or the sensor or what? Our company's mechanic seemed to think that, as long as I don't blow out my filter or any seals, everything would be ok.
Any thoughts? I'd like to have a functioning gauge at least. I know that the stock gauge is a binary indication device, but I'd like for it to work.
#2
Mdahlgren,
The oil pressure gauge on these trucks is actually an on-off switch, one of Fords little deceptions. If the oil sending unit is working properly, then the gauge will show a normal reading. No or low oil pressure would result in the gauge going to Zero (potentially very bad). Any other reading beside normal or zero means you have a bad sending unit.
So that means that your oil sender is broken. I had a similar thing happen to mine except it read low. Go to Ford and get a new one and replace and that should fix your problem. The senders are not that expensive and are easy to get to under the engine next to the oil filter.
Good luck.
The oil pressure gauge on these trucks is actually an on-off switch, one of Fords little deceptions. If the oil sending unit is working properly, then the gauge will show a normal reading. No or low oil pressure would result in the gauge going to Zero (potentially very bad). Any other reading beside normal or zero means you have a bad sending unit.
So that means that your oil sender is broken. I had a similar thing happen to mine except it read low. Go to Ford and get a new one and replace and that should fix your problem. The senders are not that expensive and are easy to get to under the engine next to the oil filter.
Good luck.
#4
I have to disagree with both of you.
Unfortunately, there is no failure mode of a pressure sending switch that will cause a full-scale reading. The sender can only cause a "no-reading" or a "mid-scale reading", nothing else.
His problem is elsewhere, most likely in the instrument cluster. Probably a microprocessor or guage unit fault.
Steve
Unfortunately, there is no failure mode of a pressure sending switch that will cause a full-scale reading. The sender can only cause a "no-reading" or a "mid-scale reading", nothing else.
His problem is elsewhere, most likely in the instrument cluster. Probably a microprocessor or guage unit fault.
Steve
#6
You may be able to get a lead on what the situation is by looking at the dash HEC test results.
An 'OIL' test reading between 0 and 176 = a normal pressure greater than 6 psi.
At less than 6 psi or defective switch should display a number greater, between 177 anf 250.
The 'GAGE' test may prove something, the 'r' test and the 'dtc' may show something but you need most of the test information to interpet the display results.
To find this info, do an internet search using the following.
Try Ford insturment cluster testing.
This may show several sites that give the short test list but enough to be useful.
The FH site has left out 'START THE ENGINE' part of entering the test.
How it's done is hold the reset button in and start the engine. Keep it held in until the speedo shows you are in the test mode, then release.
To step thru the tests push the reset each time, but you need the info to make any sense of what you see.
An 'OIL' test reading between 0 and 176 = a normal pressure greater than 6 psi.
At less than 6 psi or defective switch should display a number greater, between 177 anf 250.
The 'GAGE' test may prove something, the 'r' test and the 'dtc' may show something but you need most of the test information to interpet the display results.
To find this info, do an internet search using the following.
Try Ford insturment cluster testing.
This may show several sites that give the short test list but enough to be useful.
The FH site has left out 'START THE ENGINE' part of entering the test.
How it's done is hold the reset button in and start the engine. Keep it held in until the speedo shows you are in the test mode, then release.
To step thru the tests push the reset each time, but you need the info to make any sense of what you see.
#7
Originally Posted by WLF
projectSHO89,
I don't think we are talking about a failure mode here. I think it is pegging from a short sending full power to the gauge...and my gauge did read something beside no-scale and mid-scale sooooo.
I don't think we are talking about a failure mode here. I think it is pegging from a short sending full power to the gauge...and my gauge did read something beside no-scale and mid-scale sooooo.
Since the oil pressure switch is a switched ground to a microprocessor input, a lot depends on the engineering of the microprocessor itself. In a failure mode of an open switch, the processor's input is left open, just as if the pressure were below the threshold of 6 psi. This should result in a "no-guage deflection" indication along with a LOW OIL PRESSURE light.
There is nothing in the sender that can "send full power" since the switch does not have any power source supplied to it. It's just a single-lead open-close switch that uses engine ground as its other "terminal lead". In your case, the switch likely failed so that in the "closed position", it exhibited a measureable amount of resistance instead of a closed circuit resulting in a "low" pressure indication.
If the source of the fault was the sender switch, the LOW OIL PRESSURE light would also be turned on by the HEC. No such indication was given.
It's pretty easy to eliminate the sender as a possibility or to confirm it as the culprit. Disconnect the switch (single lead) and turn the ignition switch to RUN. Guage should indiate no pressure and the LOW OIL PRESSURE light should be on. Then, connect a jumper from the disconnected lead to ground. The LOW OIL PRESURE light should go off and the guage should read in the NORMAL range. If it does, then replace the sender. If it doesn't pass this simple test, then either the instrument cluster is defective or there is a wiring harness fault that needs to be investigated.
Steve
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#8
Alternative explanation...
Someone here at work just pointed out to me that the pegging out is more likely a sticking "oil pressure relief valve" located close to the oil pump.
To repair this problem, he says, would mean having to take the engine out and drop the oil pan to access the oil pump.
In practical terms this would mean that I am in fact running too high an oil pressure, but as long as I don't blow out seals, this should not be a problem. So he says...
I should mention that the pegging out occurs only after the engine actually runs for a few seconds. It doesn't jump up as soon as I turn on the ignition, only after the engine fires up.
To repair this problem, he says, would mean having to take the engine out and drop the oil pan to access the oil pump.
In practical terms this would mean that I am in fact running too high an oil pressure, but as long as I don't blow out seals, this should not be a problem. So he says...
I should mention that the pegging out occurs only after the engine actually runs for a few seconds. It doesn't jump up as soon as I turn on the ignition, only after the engine fires up.
Last edited by mdahlgren; 09-16-2006 at 09:57 AM.
#9
Are any other gauges like that, just "on/off" indicators disguised as gauges? Maybe it's a cost-cut on newer models, because on my truck once the motor is warm and idling the oil pressure drops a little(to the "o" in normal) and then once the rpm's lift off idle it goes back up again so it seems to be an actual indicator.
#10
#11
Ford is also known for using real gauges and only running them with a oil pressure switch instead of a real oil pressure sending unit. Like my 96 thunderbird. On that all it takes is jumping a wire on the back of the circuit board and using the sending unit from an older vehicle.....they say use one from a 85 mustang, and thats what i bought, but it's the same unit that was in my 83 351 windsor van i had. Anyway the guage in my thunderbird, even though it don't have pressure numbers, reads and fluctuates as a real gauge should.
Does anybody know if this will work on a F150 and/or has anybody actually tried it?
Does anybody know if this will work on a F150 and/or has anybody actually tried it?
#12
Ford is also known for using real gauges and only running them with a oil pressure switch instead of a real oil pressure sending unit.
mdahlgen:
You can do one of several things:
1) Take the advice of someone who has no knowledge of the system used on this truck and pull your engine. You'll still have the same issue when you're done.
2) Follow my suggestion which is based on a careful study of the circuit and the service documentation (I'm an electronics tech by trade (30 years) specializing in microprocessor-controlled electromechanical systems and TMDE). I didn't just fall of a turnip truck.
3) Take it to a dealer who will look at the exact same documentation I have, perform the same test as I suggested, and likely reach the same conclusion I have
4) Or whatever you choose.
However, after looking at your last little bit of data, I'd leave open the possibility that you have a mild charging system glitch that is causing the microprocessor to deflect only one of your guages (usually it deflects all of them on a low supply voltage condition.
Steve
#13
Not ignoring your advice.
Bluegrass et al,
I am not chosing to ignore anyone. I simply added the information about the relief valve because I thought it was relevant to the question. I will try some of the suggestions and see what I come up with, starting with the simplest first.
I thank everyone for their input and appreciate you taking the time and effort to answer me.
Magnus
I am not chosing to ignore anyone. I simply added the information about the relief valve because I thought it was relevant to the question. I will try some of the suggestions and see what I come up with, starting with the simplest first.
I thank everyone for their input and appreciate you taking the time and effort to answer me.
Magnus
#14
Originally Posted by projectSHO89
My 93 Exploder had this... had a 20 ohm reisitor in series with the pressure switch. This circuit is not in that category, however. It's been quite a few years since Ford trusted their customers with a real, live oil pressure guage... It appears that don't trust us to be able to read and properly interpret one...
You know it probably not that Ford doesn't trust their customers, it's probably the fact that they realize the majority of people and completely car stupid. There was probably too many MORONS that would freak out with the gauge fluctuating and dipping down pretty low at an idol. It was probably costing them a fortune in warranty work to the dealers for them to check these vehicles when there was nothing wrong with them.
#15
So why bother with an oil 'pressure' gauge at all? An oil warning light would have done the same....
I was pleasantly surprised when I moved here and bought my F-150, that it still had an oil gauge, the last one I had was on my '65 Morris Oxford, or was it my '60 Peugeot 403 (a beautiful car well ahead of its time)
Both of those were REAL gauges, with a hose from the engine - if those gauges failed bigtime, you were wearing the oil (not a good look)
Unfortunately, Ford's take on this makes us probably LESS inclined to pay much attention to the gauges - my voltmeter reads on the 'L' of 'normal' which I might have thought was high til I joined this forum. I did a little basic test with a voltmeter to satisfy myself, though.
Not so much Ford wanting to spare dealers unnecessary warranty visits, as much as lulling the customer through the warranty period with a false sense of security...
Mdahlglen, if you want to examine it further, before you dismantle your engine, either get a mechanic to confirm all this with a real oil pressure gauge, or just buy an aftermarket gauge and see what it says.
Nothing wrong with having a real oil gauge, anyway. I imagine you can get an ok one quite cheaply.
I was pleasantly surprised when I moved here and bought my F-150, that it still had an oil gauge, the last one I had was on my '65 Morris Oxford, or was it my '60 Peugeot 403 (a beautiful car well ahead of its time)
Both of those were REAL gauges, with a hose from the engine - if those gauges failed bigtime, you were wearing the oil (not a good look)
Unfortunately, Ford's take on this makes us probably LESS inclined to pay much attention to the gauges - my voltmeter reads on the 'L' of 'normal' which I might have thought was high til I joined this forum. I did a little basic test with a voltmeter to satisfy myself, though.
Not so much Ford wanting to spare dealers unnecessary warranty visits, as much as lulling the customer through the warranty period with a false sense of security...
Mdahlglen, if you want to examine it further, before you dismantle your engine, either get a mechanic to confirm all this with a real oil pressure gauge, or just buy an aftermarket gauge and see what it says.
Nothing wrong with having a real oil gauge, anyway. I imagine you can get an ok one quite cheaply.
Last edited by pjb999@yahoo.co; 09-19-2006 at 10:50 AM.