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Discussion Topic:
Measuring Oil Pressure
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glenn_2718 |
06-23-2018 @ 11:07 AM
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Member
Posts: 30
Joined: Oct 2017
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I think my F-1 oil pressure is low. When the truck first gets going the needle only rises to about 1/4 of the way (up to the thinner line BEFORE 30). Then after the engine warms up the needle falls back to the square shaped mark at the far left of the gage face indicating very little pressure. I confirmed that the gauge is good using a 50 Ohm rheostat as outlined in the service manual. What is the best way to tap into the oil pressure system with an oil pressure reading test gage? Is the inlet to the oil filter a good place?
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carcrazy |
06-23-2018 @ 12:02 PM
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Senior
Posts: 1567
Joined: Oct 2009
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Your oil pressure sending unit in the block may have gotten a little lazy. Yes, the inlet to the oil filter is a good place to tap into the oil line to measure the engine oil pressure. I have used a T-fitting in the line going to the oil filter to provide signals to both a mechanical oil pressure gauge mounted under the instrument panel and the original electrical oil pressure gauge.
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glenn_2718 |
06-24-2018 @ 6:47 AM
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Member
Posts: 30
Joined: Oct 2017
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I was thinking of doing exactly the same thing. Does your mechanical gage agree pretty well with the electrical sending unit? Thanks for the feedback!
This message was edited by glenn_2718 on 6-24-18 @ 6:47 AM
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glenn_2718 |
06-24-2018 @ 6:47 AM
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Member
Posts: 30
Joined: Oct 2017
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I was thinking of doing exactly the same thing. Does your mechanical gage agree pretty well with the electrical sending unit? Thanks for the feedback! Big help!
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carcrazy |
06-24-2018 @ 7:14 AM
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Senior
Posts: 1567
Joined: Oct 2009
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No, the mechanical gauge and the electrical one do not agree! When the engine is hot, the electrical gauge shows 0 to 5 psi while the mechanical one will show 20 psi. When cold, the electrical one never shows more than 40 psi while the mechanical one will show 60 or more.
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GK1918 |
06-25-2018 @ 2:19 AM
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New Member
Posts: 120
Joined: Aug 2016
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I admit I am bad with math. My life long question? Most later V8s use 80# oil pump. All cars and trucks, the gage reads 0 30 80 So I guess either Ford or King Seely engineers didn't know half of 80 equals 40 yes no. I do have a mechanical oil gage as well the original on my car. Driving any speed mechanical reads 60# and the dash gage 3/4 the way at idle mechanical reads 45# dash reads just over 1/2 like its 35# so its always been a guessing game. Back to the post I think your oil sender went south. I have found some 1970s Chrysler oil senders work (something like truck with 318 V8) sam
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glenn_2718 |
06-25-2018 @ 12:07 PM
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Member
Posts: 30
Joined: Oct 2017
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Here's what I'll do step by step (in the following order) if I don't see an big improvement in oil pressure: 1. Replace the sending unit. 2. Install a T fitting in the inlet to the oil filter and install a mechanical gage. (I'll do this no matter what.) 3. Replace the oil pressure relief valve spring on the oil pump. 4. Replace the oil pump. 5. Go back to the start and replace the oil pressure gage although it passed the test as outlined in the service manual. 6. If none of this works, then I would guess that the bearings in my V-8 are worn out and I'll have to make a decision on what's next. Does anyone know what the most common cause of low oil pressure is assuming all the above steps have been taken? Worn out rear main bearing maybe? I just don't know. One thing I'm hearing from V-8 owners is that getting an accurate oil pressure reading seems to be kind of elusive. My V-8 seems to run OK. No smoke. Doesn't burn oil. No odd noises. Doesn't miss. But the low oil pressure reading concerns me.
This message was edited by glenn_2718 on 6-25-18 @ 12:08 PM
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glenn_2718 |
07-06-2018 @ 6:33 AM
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Member
Posts: 30
Joined: Oct 2017
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I checked my oil pressure gage using a 50 Ohm rheostat as outlined in the Ford shop manual. The gage checks good. I replaced the oil pressure sending unit and temporarily installed a brand new mechanical gage. The mechanical gage consistently reads about 20 psi higher than the electrical one. I'm satisfied that my oil pressure is OK. I'll just install a permanent mechanical gage and keep an eye on both gages.
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glenn_2718 |
07-06-2018 @ 6:34 AM
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Member
Posts: 30
Joined: Oct 2017
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I checked my oil pressure gage using a 50 Ohm rheostat as outlined in the Ford shop manual. The gage checks good. I replaced the oil pressure sending unit and temporarily installed a brand new mechanical gage. The mechanical gage consistently reads about 20 psi higher than the electrical one. I'm satisfied that my oil pressure is OK. I'll just install a permanent mechanical gage and keep an eye on both gages.
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