91 F150
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Joined: Dec 2003
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91 F150
Hello. I am new here and glad to meet ya'll.
I have a strange problem and was hoping someone may be able to confirm my suspicion or point me in the right direction.
The oil pressure in my 91 F150 has slowly but surely over the last couple of years gone from on the R in the word on the gauge to below the letter N. It doesnt smoke or burn oil or anything like that. Could someone tell me their initial opinion?
I have a strange problem and was hoping someone may be able to confirm my suspicion or point me in the right direction.
The oil pressure in my 91 F150 has slowly but surely over the last couple of years gone from on the R in the word on the gauge to below the letter N. It doesnt smoke or burn oil or anything like that. Could someone tell me their initial opinion?
Posting Guru
Joined: Dec 2002
Posts: 1,113
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From: Remsen, NY
Sorry everyone if I'm starting to sound like a broken record with the oil pressure gauge thing....
Beginning in 1990, Ford started putting a switch in the block instead of a variable sensor, and wired a resistor inline with the oil pressure gauge. The effect is that the gauge shows nothing for under 6-8 psi. Then the switch triggers over that level and the gauge immediately goes up to just over halfway.
Now, you or someone else could have pulled the cluster, soldered across the resistor and replaced the sensor with the bigger bell shaped one.
First look at the sensor, it's just toward the back of the truck from the oil filter. If it's just under an inch across, it's the switch and the reading is bogus.
Why it would read lower if it's the stock '91 setup, I'm not sure, but it would have to be an electrical thing...
Put a mechanical gauge on it to confirm what's going on before you do anything.
Beginning in 1990, Ford started putting a switch in the block instead of a variable sensor, and wired a resistor inline with the oil pressure gauge. The effect is that the gauge shows nothing for under 6-8 psi. Then the switch triggers over that level and the gauge immediately goes up to just over halfway.
Now, you or someone else could have pulled the cluster, soldered across the resistor and replaced the sensor with the bigger bell shaped one.
First look at the sensor, it's just toward the back of the truck from the oil filter. If it's just under an inch across, it's the switch and the reading is bogus.
Why it would read lower if it's the stock '91 setup, I'm not sure, but it would have to be an electrical thing...
Put a mechanical gauge on it to confirm what's going on before you do anything.
Post Fiend
Joined: Nov 2001
Posts: 14,947
Likes: 6
From: Topsfield, MA
Over time the bearings wear out inside the engine and the gaps cause pressure loss. The way to tell is that the pressure is good when the engine is cold, but drops when the engine warms up. This is because the oil thins out when it's warmer. Get a gauge and check to see what the engine is actually doing, then go from there.
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