Like a few other F150 owners I’ve spoken with, my 1997 F150 was plagued by an erratic oil pressure gauge. Specifically, when cold, the gauge would work normally. However, after the truck was completely warmed up (I commute about 25 miles each way to work), the gauge would begin dropping down, sometimes to the point of setting off the oil pressure light. Sometimes I could get the needle to begin reading normally again by fluctuating the engine RPM, but this “fix” was hit or miss. Although I was quite confident that the gauge was indeed malfunctioning, I could not completely ignore the fear that I really was dealing with an actual pressure drop.
A few days ago, I traced the wire leading from the oil pressure sensor (located very near the oil filter) to (behind) the dash. What I found was that the wire, encased in a high temperature insulator, was routed VERY close to the exhaust manifold (within an eighth of an inch). I theorized that, although not burnt, the wire’s electrical properties were being changed by the ambient high exhaust heat. I rerouted the wire completely away from the exhaust system (after encasing it in new loom/split casing), crossed my fingers, and went driving.
A final thought – I do still believe it to be a VERY good idea to install a “real” oil pressure gauge as many on this board have recommended; I plan on installing a mechanical one in the next week or so. Anyhow, sorry for the long-winded post, but perhaps it’ll help someone, as reading many of you all’s questions/responses on this board has helped me.
my 2000 f150 does the exact oppisite. when it is cold the pressure gage bounces from normal to low and sets off the light. once it warms up it goes away. it is really driving me nuts and I hope that someone knows what the problem is and how to fix it.
I don't bother to install a "real" pressure gauge on my vehicles with dash gauges. I did spend the $40 on a oil pressure test gauge. On most engines it only takes the time of an oil change to do the test. It sure beats driving around wondering if you are destroying an engine.
Was this wiring problem caused by improperly routed wires? Does this possibly happen when someone pulls on the wire further down the line? Thanks for the tip, I'll look at the routing on mine the next time I do an oil change.
Originally posted by NCHorseplay my 2000 f150 does the exact oppisite. when it is cold the pressure gage bounces from normal to low and sets off the light. once it warms up it goes away. it is really driving me nuts and I hope that someone knows what the problem is and how to fix it.
Clogged oil screen (In oil pan).
I can't answer in complete certainty whether the wire was misrouted - I bought the truck used, so it could have been molested by someone along the line. That said, I really don't think that the wire was moved. Before I relocated it, the wire was nicely nestled amongst other wires in what appeared to be an undisturbed factory loom. In fact, I had to remove it from this loom in order to reroute it. Additionally, the wire is encased in a high temperature wire protector/casing, suggesting that the wire was factory routed in close proximity to the exhaust.
When cold, mine will fluctuate but will eventually read normal after warming up. Note: I just changed my oil and used 5W20. It had almost cured the problem completely except for one time right after the oil change. Its a lighter oil and maybe this points to a failing pump. I dont know.
Im thinking that maybe the fluctuating was caused by low oil level rather than a bad pump or sending unit or wire ............
Lighter oils are recommended for cold temperatures. The pump is going to have a hard time pumping thick oil. If the gauge goes normal when it is warmed up then maybe the oil warmed up and can flow good.
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