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oil pressure gauge
#1
Hi folks

I have revised my 351 Cleveland completely and I'm now testing it on the streets.

After a 150 miles trip with some stops and some restarts without any issues, close to home I stopped at a gas station to refill my gas tank. After this stop, engine didn't start at the first turn of the key. Sounded like the starter wasn't hardly able to turn the motor. I stopped igniting and turned the key again after a few seconds. Engine starts and revs up without any hesitation. Then I noticed, that the oil pressure gauge only shows in the middle of the gauge. Before this, is shows close to maximum. I headed home (less than 2 mls), checked all the fluids and wiring; everything ok. Also no strange sound from the engine.

After two hours I started it again and the gauge was close to maximum again.

[Image: Zusatzinstrumente.jpg]

Today another 50 miles testdrive with several stops and restarts of the engine. After the third restart, gauge stopped again in the middle, close to the I from the OIL writing there. Again no strange noise from the motor, all fluids on correct level. All other gauges are working well. I also recognized, that the index needle is moving a little bit. It doesn't look like it is blocked internally.

Now I want to measure the voltage or better said the resistance of the sensor.

Can anybody provide me the figures, this sensor has to respond at different pressure conditions?

If I have to change the sensor, can I go with one from STANDARD, Rockauto is offering for less than 7 bucks, or should I opt for the Motorcraft sensor, offered for roughly 24 Dollars? Is it worth it?

Please let me know your thoughts.

Cheers
Frank
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#2
(05-17-2020, 08:13 AM)Vicus Wrote: Hi folks

I have revised my 351 Cleveland completely and I'm now testing it on the streets.

After a 150 miles trip with some stops and some restarts without any issues, close to home I stopped at a gas station to refill my gas tank. After this stop, engine didn't start at the first turn of the key. Sounded like the starter wasn't hardly able to turn the motor. I stopped igniting and turned the key again after a few seconds. Engine starts and revs up without any hesitation. Then I noticed, that the oil pressure gauge only shows in the middle of the gauge. Before this, is shows close to maximum. I headed home (less than 2 mls), checked all the fluids and wiring; everything ok. Also no strange sound from the engine.

After two hours I started it again and the gauge was close to maximum again.

[Image: Zusatzinstrumente.jpg]

Today another 50 miles testdrive with several stops and restarts of the engine. After the third restart, gauge stopped again in the middle, close to the I from the OIL writing there. Again no strange noise from the motor, all fluids on correct level. All other gauges are working well. I also recognized, that the index needle is moving a little bit. It doesn't look like it is blocked internally.

Now I want to measure the voltage or better said the resistance of the sensor.

Can anybody provide me the figures, this sensor has to respond at different pressure conditions?

If I have to change the sensor, can I go with one from STANDARD, Rockauto is offering for less than 7 bucks, or should I opt for the Motorcraft sensor, offered for roughly 24 Dollars? Is it worth it?

Please let me know your thoughts.

Cheers
Frank
You could have a flakey connection which is adding resistance (lower reading) at times. You shouldn't be seeing that high an oil pressure reading on a stock engine, though...

I'd check your oil sending unit wire connection at the sending unit, the plug to the headlight harness near the firewall, and the plug at the gauge to see if all are clean and free of corrosion.  Of still flakey, I'd get a mechanical sending unit and tee it off to compare to the electrical unit.

Let me check your shorts!
http://midlifeharness.com

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#3
(05-17-2020, 11:03 AM)midlife Wrote:
(05-17-2020, 08:13 AM)Vicus Wrote: Hi folks

I have revised my 351 Cleveland completely and I'm now testing it on the streets.

After a 150 miles trip with some stops and some restarts without any issues, close to home I stopped at a gas station to refill my gas tank. After this stop, engine didn't start at the first turn of the key. Sounded like the starter wasn't hardly able to turn the motor. I stopped igniting and turned the key again after a few seconds. Engine starts and revs up without any hesitation. Then I noticed, that the oil pressure gauge only shows in the middle of the gauge. Before this, is shows close to maximum. I headed home (less than 2 mls), checked all the fluids and wiring; everything ok. Also no strange sound from the engine.

After two hours I started it again and the gauge was close to maximum again.

[Image: Zusatzinstrumente.jpg]

Today another 50 miles testdrive with several stops and restarts of the engine. After the third restart, gauge stopped again in the middle, close to the I from the OIL writing there. Again no strange noise from the motor, all fluids on correct level. All other gauges are working well. I also recognized, that the index needle is moving a little bit. It doesn't look like it is blocked internally.

Now I want to measure the voltage or better said the resistance of the sensor.

Can anybody provide me the figures, this sensor has to respond at different pressure conditions?

If I have to change the sensor, can I go with one from STANDARD, Rockauto is offering for less than 7 bucks, or should I opt for the Motorcraft sensor, offered for roughly 24 Dollars? Is it worth it?

Please let me know your thoughts.

Cheers
Frank
You could have a flakey connection which is adding resistance (lower reading) at times. You shouldn't be seeing that high an oil pressure reading on a stock engine, though...

I'd check your oil sending unit wire connection at the sending unit, the plug to the headlight harness near the firewall, and the plug at the gauge to see if all are clean and free of corrosion.  Of still flakey, I'd get a mechanical sending unit and tee it off to compare to the electrical unit.
Randy

Thank you very much for your comment. I will check with a mechanical gauge and revert.

Regarding the high pressure reading, the engine is completely revised and got a new Melling oil pump, but standard volume and standard pressure. Still too much reading?

Cheers Frank
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#4
I have a recently rebuilt 351 4V  Cleveland engine with a Melling standard volume oil pump too. I did have an aftermarket electric oil gauge with matching sender and was getting some weird oil pressure readings. I guess the sender went or is going bad? Anyway I just add a mechanical gauge and it isn’t doing any of the weird readings anymore. But, it does read about 80 psi @ cold idle, then as low as 30 psi @ hot idle. I’m around 45-50 cruising around town. I do feel more reassured having the mechanical gauge and as long as you have at least 10 psi per 1000 rpms then you’re good to go.

run_horse Run Horse Run!
John 72 Q Code
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#5
(05-17-2020, 06:03 PM)jpaz Wrote: I have a recently rebuilt 351 4V  Cleveland engine with a Melling standard volume oil pump too. I did have an aftermarket electric oil gauge with matching sender and was getting some weird oil pressure readings. I guess the sender went or is going bad? Anyway I just add a mechanical gauge and it isn’t doing any of the weird readings anymore. But, it does read about 80 psi @ cold idle, then as low as 30 psi @ hot idle. I’m around 45-50 cruising around town. I do feel more reassured having the mechanical gauge and as long as you have at least 10 psi per 1000 rpms then you’re good to go.
 John, I'm curious. This might also be helpful to Frank as well. We both have the same Melling oil pump and I don't think our motors are so much different. What I see on mine is about 75 hot at idle and only drops to 60 running. I have never seen it drop anywhere near 30 or even 45 psi.
So why the difference? Your new mechanical gauge is a Bosch I believe, so even though the face is different, the parts inside ought to be at least similar. I would think that the readings on the two gauges would be close to each other unless there are factors I'm not realizing.

Geoff.
 I learn something new every day!
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#6
(05-17-2020, 06:49 PM)Stanglover Wrote:
(05-17-2020, 06:03 PM)jpaz Wrote: I have a recently rebuilt 351 4V  Cleveland engine with a Melling standard volume oil pump too. I did have an aftermarket electric oil gauge with matching sender and was getting some weird oil pressure readings. I guess the sender went or is going bad? Anyway I just add a mechanical gauge and it isn’t doing any of the weird readings anymore. But, it does read about 80 psi @ cold idle, then as low as 30 psi @ hot idle. I’m around 45-50 cruising around town. I do feel more reassured having the mechanical gauge and as long as you have at least 10 psi per 1000 rpms then you’re good to go.
 John, I'm curious. This might also be helpful to Frank as well. We both have the same Melling oil pump and I don't think our motors are so much different. What I see on mine is about 75 hot at idle and only drops to 60 running. I have never seen it drop anywhere near 30 or even 45 psi.
So why the difference? Your new mechanical gauge is a Bosch I believe, so even though the face is different, the parts inside ought to be at least similar. I would think that the readings on the two gauges would be close to each other unless there are factors I'm not realizing.

I don’t know why the difference, but that’s what it says. I do have a Bosch mechanical gauge. You have 75 hot idle and 60 cruising? That doesn’t sound right, you must mean the the other way around.
Sorry Vicus, not try to hijack your thread.

run_horse Run Horse Run!
John 72 Q Code
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#7
Check your grounds. Coupled with the difficulty starting, you might have a loose, bad or missing connection in the battery -> fender apron -> block ground cable.


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#8
With that much invested wouldn't a copper tube mechanical gauge be the ticket for accuracy?  My engine isnt in yet but I already run a copper tube and mounted a mechanical oil presure gauge. I also have the center console 3 gauge pack. So, I have 2 gauges checking oil presure.

Just sayin.
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#9
(05-18-2020, 12:26 AM)machattack Wrote: With that much invested wouldn't a copper tube mechanical gauge be the ticket for accuracy?  My engine isnt in yet but I already run a copper tube and mounted a mechanical oil presure gauge. I also have the center console 3 gauge pack. So, I have 2 gauges checking oil presure.

Just sayin.
Rod

Y adaptor to connect two sensors is already purchased. At first I will go with a temporary solution to  get back the trust in my own work. Final installation of a mechanical oil pressure gauge will follow but I will opt to a CuNiFe10 tube.

Cheers Frank
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#10
(05-17-2020, 10:21 PM)Hemikiller Wrote: Check your grounds. Coupled with the difficulty starting, you might have a loose, bad or missing connection in the battery -> fender apron -> block ground cable.
Very good idea! I will check and revert.

Cheers Frank
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