Oil pressure weird

Torqued · #1 10-08-2006, 08:33 PM

I changed the oil and filter on my 88 F250 and ever since then the oil pressure is running at the bottom end of the normal band. It's a 351W and the oil pressure gauge has always been in ther middle of the band until now. I haven't had time to put a direct reading gauge on it yet but I was wondering if it was possible for a faulty oil filter to cause this?

Torqued

mustangmike351c · #2 10-08-2006, 08:40 PM

if you had good pressure before I would say you got a piece of carbon in the sending unit fitting or the sensor has just gone bad

unclebubbles · #3 10-08-2006, 10:24 PM

Does youre gauge move at all when the engine starts now, or is it resting in the same spot on the low side? Is it possible you knocked the sensor wire loose when you changed the filter?

corning_d3 · #4 10-08-2006, 11:14 PM

A lot of the later model fords don't show actual oil pressure. The guage only shows that you have pressure, but not how much. I'm not 100% sure if this is the case on an '88, however..

VinceH · #5 10-09-2006, 01:56 PM

I am having the same issue with my 92. Its a351w as well but the gauge will read bellow the N and some times will run in the middle and than back down. All of the sudden it has been very inconsistant, any help would be great.

unclebubbles · #6 10-09-2006, 02:49 PM

As stated in a post above, most late model vehicles dont actually tell you how much oil pressure you have. The (sending unit) is actually an oil pressure switch. Anything above about 5# of pressure turns it on, and gives a gauge reading of 1/2 to 3/4 scale , anything less than 5# , its off with no gauge reading. Older vehicles(some late models still have it) , had a variable resistor as the sending unit. As the pressure varied, the resistance varied, and controlled current to the gauge. This gave a reading that varied with the oil pressure. The best way to find out for sure what your pressure is, is to take out the switch/sending unit, and install a manual (direct reading) gauge. You can fabricate one for less than10$, with a gauge and a few fittings from your parts store. Or you can buy one already assembled. This will tell you for sure what the pressure is. If the pressure is ok, the problem is usually the switch/sending unit, the dash gauges do go bad occasionally, but very seldom.

VinceH · #7 10-09-2006, 05:36 PM

That helps, Thanks

VinceH · #8 10-09-2006, 06:52 PM

Has anyone replaced the sending unit/ presure switch? How difficult is it?

Torqued · #9 10-10-2006, 01:41 AM

As far as I can tell, this truck has a separate sending unit that reads pressure on the gauge, not a switch. That's what my manual says. I did start it one time and the gauge popped back up to where it normally was. This lasted until I shut it off. Next start it was at the low end again. The gauge does drop down to the low peg when the engine is off, so it's not stuck. I'll get under the hood soon and try a direct reading gauge. Too many more interesting things to do for now.

Torqued

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