Making oil pressure gauge give precise reading?
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Mountain Pass
Joined: Jun 2024
Posts: 114
Likes: 4
Making oil pressure gauge give precise reading?
I've heard the oil pressure gauge is a dummy gauge, and Is actually an on/off switch and will only read low if it's below a certain threshold. Is it possible to modify the gauge so that it actually will move up and down based on the oil pressure in real time?
for reference I have a 97 f250hd with the 351W.
for reference I have a 97 f250hd with the 351W.
Hotshot
Joined: Jun 2015
Posts: 12,768
Likes: 2,420
I made this modification several years ago but I have an ‘89. I think you can do it on the ‘92-96/7 cluster as well but I might be wrong. I don’t believe the article I used isn’t still available but there might be a thread somewhere online. There is a resistor on the back of the cluster. Bypass the resistor and swap out the oil pressure switch for a sending unit from an ‘87 or older engine.
Logistics Pro
Joined: Mar 2012
Posts: 3,507
Likes: 121
From: Oregon
Pull the cluster out and you will see a resistor as stated above for the oil pressure gauge. I soldered a wire around it. Installed a Motorcraft SW1547B switch. You will have to get some pipe fittings to space the sender out as it will not fit where the factory switch is. At least it didn’t on mine…
Hotshot
Joined: Jun 2015
Posts: 12,768
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I got mine from the junkyard.
Lead Driver
Joined: Jun 2021
Posts: 5,208
Likes: 798
On '92-95, the resistor is on the instrument cluster film circuit. I normally make the jumper wire long enough to hang down below the cluster so it can be cut if a future owner chooses to convert back to the original switch & have an idiot-gauge again
96-97 trucks need to use a 92-95 oil pressure gauge to work for this mod
Cargo Master
Joined: Mar 2007
Posts: 2,757
Likes: 999
I've heard about this 'mod' for some time, but does this apply to all of these OBS Fords? I have a 1995 F250 and I swear my gauge seems to vary with engine temp/RPM. Is it because I have an XLT which might just have enough options to get the real oil pressure gauge?
Any input would be appreciated.
Any input would be appreciated.
Logistics Pro
Joined: Aug 2014
Posts: 3,547
Likes: 845
I've heard about this 'mod' for some time, but does this apply to all of these OBS Fords? I have a 1995 F250 and I swear my gauge seems to vary with engine temp/RPM. Is it because I have an XLT which might just have enough options to get the real oil pressure gauge?
Any input would be appreciated.
Any input would be appreciated.
Then I thought, maybe previous owner did this mod?
What I really need to do, is hook up a DVOM, record and monitor that on the sensor, from cold start to warm up, and driving at various engine speeds.
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Cargo Master
Joined: Oct 2011
Posts: 2,233
Likes: 297
From: Kenner,La.
Oil pressure
To make mounting the sender easy I use a stainless steel hose from a Mercruiser trim system to mount the sender Remotely. This also grounds the sender.
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Cargo Master
Joined: Mar 2007
Posts: 2,757
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I am the second owner. I have owned this since 97. I am suspecting it was a lease return truck. I think I got a good deal back then. Not very desirable [but affordable]. 2WD, 5.8L, E4OD, 3.55 and Calif emissions. I am certain there were no mods done.
There was a time I noticed a substantial lower oil pressure reading. I pulled over and checked the oil level. It was good. Oil pressure tends not to just fail with 100k miles and great oil services. I just assumed it was a bad sender. Once I put a new sender on it, it was back to normal.
There was a time I noticed a substantial lower oil pressure reading. I pulled over and checked the oil level. It was good. Oil pressure tends not to just fail with 100k miles and great oil services. I just assumed it was a bad sender. Once I put a new sender on it, it was back to normal.
Hotshot
Joined: Jun 2015
Posts: 12,768
Likes: 2,420
My gauge swings with temp/rpm as well. I recorded a video of it recently.
Then I thought, maybe previous owner did this mod?
What I really need to do, is hook up a DVOM, record and monitor that on the sensor, from cold start to warm up, and driving at various engine speeds.
Then I thought, maybe previous owner did this mod?
What I really need to do, is hook up a DVOM, record and monitor that on the sensor, from cold start to warm up, and driving at various engine speeds.
Laughing Gas
Joined: Oct 2014
Posts: 943
Likes: 184
From: Carnation, Wah
I've heard about this 'mod' for some time, but does this apply to all of these OBS Fords? I have a 1995 F250 and I swear my gauge seems to vary with engine temp/RPM. Is it because I have an XLT which might just have enough options to get the real oil pressure gauge?
Any input would be appreciated.
Any input would be appreciated.
I have an aftermarket pressure gauge, and
the reading doesn't remotely track what the dummy gauge does. If it did, it would
read higher on a cold start, and drop as the engine warms. It usually does the reverse of that.
I got the sender to modify the stock gauge, but after watching what it does with
a 20 ohm resistor, came to the conclusion that
"precise reading"
was so far outside this gauge's ability that it wasn't worth the effort.
Classic Ford- the voltmeter is quite precise, the 'oil pressure' is complete junk.
t
Hotshot
Joined: Jun 2015
Posts: 12,768
Likes: 2,420
I got the sender to modify the stock gauge, but after watching what it does with
a 20 ohm resistor, came to the conclusion that
"precise reading"
was so far outside this gauge's ability that it wasn't worth the effort.
a 20 ohm resistor, came to the conclusion that
"precise reading"
was so far outside this gauge's ability that it wasn't worth the effort.
Lead Driver
Joined: Jun 2021
Posts: 5,208
Likes: 798
Ford added the resistor because stupid customers complained that the gauge moved too much. Once you bypass the resistor and use an actual sending unit instead of an on/off pressure switch it goes back to being a real gauge. The downside is that it still doesn’t have numbers to indicate actual pressure.
The gauge on mine is also acts with a small amount of sweep, almost assuredly related to system voltage at that very moment ,
Cargo Master
Joined: Mar 2007
Posts: 2,757
Likes: 999
All too often, people get fixated on gauges and often say the sky is falling way before it is.
Many manufacturers use smart gauges. Coolant gauges that always read in the middle unless there is an extreme temperature swing. Working in the service industry, this resolved most of the complaints that customers had. People don't get that at different conditions things change. They expected and demanded that it's the same. So, the factory did that. Who is to blame? The clients and they got what they deserve.
I recently worked on a Porsche Cayenne twin turbo V8, yeah, it's not Ford but their engine coolant temperature gauge reads 200F. Stays in the middle once the engine warms up. If you got good test equipment, the engine runs anywhere from 220F to 230F. There is no way any client will accept that it's ok for the engine to run at 230F. So, to prevent issues, it reads a number that they will like. Problem solved. Those smart gauges save everyone stress.
What was that movie? "You can't handle the truth!"
Many manufacturers use smart gauges. Coolant gauges that always read in the middle unless there is an extreme temperature swing. Working in the service industry, this resolved most of the complaints that customers had. People don't get that at different conditions things change. They expected and demanded that it's the same. So, the factory did that. Who is to blame? The clients and they got what they deserve.
I recently worked on a Porsche Cayenne twin turbo V8, yeah, it's not Ford but their engine coolant temperature gauge reads 200F. Stays in the middle once the engine warms up. If you got good test equipment, the engine runs anywhere from 220F to 230F. There is no way any client will accept that it's ok for the engine to run at 230F. So, to prevent issues, it reads a number that they will like. Problem solved. Those smart gauges save everyone stress.
What was that movie? "You can't handle the truth!"