Oil pressure gage acting weird

I have a 1990 F150 with the 302 engine, and since it has started getting cold here the oil pressure gauge is acting funky. Normally when I start the engine the gauge goes to about the middle of the normal range, but when it is cold out, it sits right at the line on the low side of the normal range. The gauge will sit right on the low mark for about 2 or 3 miles and then all of a sudden it pops right over to the middle of the normal range. Any idea why this is doing this? I haven't ever seen this on a vehicle, and this is the first winter I am driving this truck.

TIA

Chris

Reply to
c
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I'd probably do an oil/filter change and see if there's a change, and if not, then put a mechanical gauge on it for a day or two and see what's really going on.

Dave

Reply to
David Ward

On Tue, 25 Nov 2003 12:56:21 +0000, David Ward rearranged some electrons to form:

Factory gauges are notoriously inaccurate. In fact many are simply idiot lights disguised as gauges. I would call them "indicators" rather than gauges.

Reply to
David M

Actually the oil was changed about 500 miles ago, so I really don't think that is it. It could be the bypass, but the bypass would let the pressure get to whatever rating it opens at, which would have to be more than what the gauge reads under normal conditions. I'm starting to think the cold is just messing with the gauge or sending unit somehow. It does this religiously when I start the truck for the first time in the morning when the temp is below 25F. Once it runs for a bit, the gauge all of a sudden jumps up to right in the middle of the normal range and it fine the rest of the day, even if the truck sits for quite a while. The engine isn't making any noises like it is low on pressure, so I guess I'll just ignore it. I was just wondering if anyone had a similar experience. Thanks for the replies.

Chris

Reply to
c

On Tue, 25 Nov 2003 16:02:07 +0000, c rearranged some electrons to form:

As the other Dave said, it might be wise to hook up a mechanical gauge just to make sure...

Reply to
David M

Mine goes all over the place, reading real low in wet weather. I suspect my sensor just needs replacing.

Reply to
Ken Finney

|I have a 1990 F150 with the 302 engine, and since it has started getting |cold here the oil pressure gauge is acting funky. Normally when I start the |engine the gauge goes to about the middle of the normal range, but when it |is cold out, it sits right at the line on the low side of the normal range. |The gauge will sit right on the low mark for about 2 or 3 miles and then all |of a sudden it pops right over to the middle of the normal range. Any idea |why this is doing this? I haven't ever seen this on a vehicle, and this is |the first winter I am driving this truck.

I'd sure change that oil filter. Get a Wix or other high-quality filter. Don't use a Fram

Rex in Fort Worth

Reply to
Rex B

Sending units (for the "gauge") are really cheap and easy to replace, you may want to start there and see if that takes care of it. Secondly, most of these sending units are sort of redundant. There is one for the gauge on the dash and one for the EEC unit that controls your engine/transmission. Look on the net for the self diagnostic test instructions (again very easy, just grounding a pin, turning the key on, watching the engine light flash) and run the test to get any stored codes. If your oil pressure had dropped to a dangerous level at any point, there would likely have been a code set that will show up in the test. If no code then you can be sure the EEC sending unit (which is much more accurate and expensive) is working and sensing a proper pressure and the problem is not critical.

Reply to
BunnMan

Thanks,

There are no codes there. I'm sure this is just the sending unit acting funky when it is cold outside. We just had a warm day and the thing went right to the middle of the gauge as soon as I started the truck. the other thing is that it only does this the first time in the morning, even if the truck sits outside for several hours. I'm going to pop a new sending unit in it and leave it at that. Thanks to you and everyone else that responded.

Chris

Reply to
c

No. You are not sure. ;) (just feel/think you are?)

Well you'll "know more" after that, "for sure". ;)

Alvin in AZ (and a general pain in the ass)

Reply to
alvinj

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