Oil Pressure
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New User
Joined: Jun 2005
Posts: 21
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From: western washington
Oil Pressure
I have a 1990 f350 with a 460 it has 135,000 miles and the oil pressure is on the N to the O in normal i have heard that these oil pressure gauges arent really reliable how can i check my oil pressure mechanically and what pressure should it be at?
Senior User
Joined: Apr 2003
Posts: 448
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From: Edmonton, AB Canada
remove the stock sending unit and get a cheap mechanical oil pressure gauge. It will thread right into the hole. Your oil pressure should be around 30-60psi at idle and typically changes as rpm changes. If it is still in the normal range and isnt knocking, then I wouldnt worry to much about it, other than stepping up the amount of oil changes you do per year to help that big motor along. Good luck
Fleet Mechanic
Joined: Nov 2003
Posts: 1,372
Likes: 14
From: West Cornwall, CT
The oil pressure gage does not indicate actual oil pressure. The oil pressure sensor is a switch and when it sees about 10 psi it closes and supplies voltage to your "gage". If the gage indicates anything at all it means the switch is closed.
To read real oil pressure you would have to install an oil pressure sensor that would provide a resistance proportional to oil pressure and modify the wiring to your present gage. I'm sure that someone has done this modification before and knows what parts will work.
If you need to determine actual oil pressure, you could also install a temporary mechanical pressure gage in parallel with the normal sensor. This would require finding the right fittings but should be easy enough to do.
Lou Braun
To read real oil pressure you would have to install an oil pressure sensor that would provide a resistance proportional to oil pressure and modify the wiring to your present gage. I'm sure that someone has done this modification before and knows what parts will work.
If you need to determine actual oil pressure, you could also install a temporary mechanical pressure gage in parallel with the normal sensor. This would require finding the right fittings but should be easy enough to do.
Lou Braun
Senior User
Joined: Apr 2003
Posts: 448
Likes: 0
From: Edmonton, AB Canada
Lau Braun, if that is the case then why does ford use a 20 ohm resistor in the circuit board in the oil pressure gauge section of the 92 and later trucks? Also, why would there be a range if all it indicated was "yay oil pressure" or "oh crap no oil pressure"? Hell, even in my old bronco i have a range, and i have more oil pressure when it is cold compared to when it is warm, which is confirmed with the mechanical trio of gauges that I installed? I am sorry to say but that might be the case with a oil pressure light, but i am afraid i dont think ford would have used a gauge if it wasnt designed to show a differentiation in something. That defeats the purpose of said gauge. And wouldnt the temp gauge work in the same fasion as it runs of a "switch" as well? I will agree that the sending unit is not termed a sensor, but i have to disagree that it acts exactly like a simple switch.
Last edited by Tdvjensen; Dec 8, 2006 at 07:36 PM.
