Intermittent Oil Pressure only After Long Trips?

I have a 2002 Ford Ranger that doesn't have a real oil pressure gauge
- it has one of those "fake" gauges that always shows either zero or
half scale. The oil pressure has always behaved normally (i.e. it's
not zero :-) until a couple weeks ago when we took it for about a two
hour drive.

It was fine on the freeway but when the engine was idling in the
hotel parking lot I noticed that the gauge was "twitching". Since the
gauge can't actually show any real values, my guess is that it's just
intermittently oscillating between zero and normal, but the gauge is
too heavily damped for it make the full swing. No warning lights, if
that matters.

I shut it off and it sat there in the lot for about an hour, and when
I cautiously started it up about an hour later it was normal again.
Steady pressure reading. In a couple of days of short trips driving
around town it behaved perfectly normally.

Until, that is, we took a two hour drive to get back home, and by the
end of that trip, it was doing the exact same thing again. But since
then it still behaves normally for trips, even as long as 30-40
minutes, around town.

Even a 30 minute trip seems like it should be enough to get the
engine and the oil plenty hot, especially with the A/C running and the
hot weather. I just can't think of anything that fail after two hours
that wouldn't do the same thing sooner, and it's really difficult to
troubleshoot a problem that requires two hours of driving to reproduce!

Any guesses as to what might cause this?

Thanks,
Bob Armstrong

wrote:
> I have a 2002 Ford Ranger that doesn't have a real oil pressure gauge
> - it has one of those "fake" gauges that always shows either zero or
> half scale. The oil pressure has always behaved normally (i.e. it's
> not zero :-) until a couple weeks ago when we took it for about a two
> hour drive.
>
> It was fine on the freeway but when the engine was idling in the
> hotel parking lot I noticed that the gauge was "twitching". Since the
> gauge can't actually show any real values, my guess is that it's just
> intermittently oscillating between zero and normal, but the gauge is
> too heavily damped for it make the full swing. No warning lights, if
> that matters.
>
> I shut it off and it sat there in the lot for about an hour, and when
> I cautiously started it up about an hour later it was normal again.
> Steady pressure reading. In a couple of days of short trips driving
> around town it behaved perfectly normally.
>
> Until, that is, we took a two hour drive to get back home, and by the
> end of that trip, it was doing the exact same thing again. But since
> then it still behaves normally for trips, even as long as 30-40
> minutes, around town.
>
> Even a 30 minute trip seems like it should be enough to get the
> engine and the oil plenty hot, especially with the A/C running and the
> hot weather. I just can't think of anything that fail after two hours
> that wouldn't do the same thing sooner, and it's really difficult to
> troubleshoot a problem that requires two hours of driving to reproduce!
>
> Any guesses as to what might cause this?
>
> Thanks,
> Bob Armstrong

I am gonna go with Oil Pressure Sensor I had one fail and it was very
'twitchy' under a certain pressure aka low revs/idle before it stopped
completely, I put an aftermarket guage on it as I had a spare one and
had tried other easy fix.

2ofdem wrote:
> I am gonna go with Oil Pressure Sensor I had one fail and it was very
> 'twitchy' under a certain pressure aka low revs/idle before it stopped
> completely, I put an aftermarket guage on it as I had a spare one and
> had tried other easy fix.

Yep, that sounds like the same problem except that mine only seems to
get flaky after a couple of hours of continuous driving.

It'd be really nice if it was just a bad oil pressure sender, but I
wish there were some easy way to independently confirm that. None of
the alternatives are very pretty :-)

Does anybody know if it's possible, in one of these Fords with the
"fake" gauge, to replace the pressure switch sender with a real analog
one (maybe from an older Ranger?) and get a real, functional, gauge?

Thanks,
Bob

wrote:
> 2ofdem wrote:
> > I am gonna go with Oil Pressure Sensor I had one fail and it was very
> > 'twitchy' under a certain pressure aka low revs/idle before it stopped
> > completely, I put an aftermarket guage on it as I had a spare one and
> > had tried other easy fix.
>
> Yep, that sounds like the same problem except that mine only seems to
> get flaky after a couple of hours of continuous driving.
>
> It'd be really nice if it was just a bad oil pressure sender, but I
> wish there were some easy way to independently confirm that. None of
> the alternatives are very pretty :-)
>
> Does anybody know if it's possible, in one of these Fords with the
> "fake" gauge, to replace the pressure switch sender with a real analog
> one (maybe from an older Ranger?) and get a real, functional, gauge?
>
> Thanks,
> Bob

you could always tee off the sender and run a line into the cabin and
hang a mechanical pressure gauge under the dash. I think I'd do that,
especially if you can figure out how to do it temporarily, to verify
that you don't actually have a low oil pressure at hot idle problem.

good luck,

nate

2ofdem wrote:
>
> I am gonna go with Oil Pressure Sensor I had one fail and it was very
> 'twitchy' under a certain pressure aka low revs/idle before it stopped
> completely, I put an aftermarket guage on it as I had a spare one and
> had tried other easy fix.
>

I'd second that.

What about replacing the factory sending unit and gauge with a decent
aftermarket one?

When the wife's Beretta's sending unit went, the gauge would creep up
and flash (digital dash) after pegging, then drop to 0 and start
climbing back up. Rather entertaining, but useless...

My old Jimmy's gauge was so bouncy as to be unusable.

Ray