Again, An Oil Pressure Querry

[JamesSam]

My oil pressure gauge has been doing some funny stuff. Specifically maxing out beyond 60 psi, like the sending unit is bad or disconnected, when coming to a stop, after a trip, and just before shutting off.

While driving it perks up to between 40-50 psi, which is perfectly fine with me. When I first noticed this happening recently I checked the oil and it was a bit shy so I added a half a quart, and it is still acting up.

My thoughts are I need to get under the truck and likely will need to wipe away some excess oil and check the connection on the sending unit. Maybe the sending unit is fading out? I replaced it about a year, maybe two years ago.

I have driven the truck to work and run errands today so waiting for it to cool and plan to check the oil level again.

So, has anyone here had this particular oil pressure guage experience? I know the 80's factory gauge for oil pressure is not as exact as most after market ones these days, but it does give me a sense of normalcy to see it read in the acceptable range.

 

[Terlingueno]

My OEM oil "gauge" is an idiot light. Engine is a 350.

Sooo...

Back in 2007 I installed an Auto Gage set with 2 5/8" Oil, Water and Volt gauges. Since that time, at start up oil gauge goes up to appx 60psi, after a few minutes warm up, drops to 50ish, then as I am driving, settles down to appx 40psi. At idle it runs a little more than 20.

Seems normal to me.

Oil is Valvoline VR1 10w30

 

[Ricko1966]

Oil level is not causing your problem,anywhere between the 2 marks is spec. I run on the low mark,not the high mark,there are advantages and disadvantages to each way. Intermittent gauge reading is most likely,the sender,the wires or the gauge itself,but possibly a sticking pressure relief valve. You should put a mechanical gauge on it and verify you do or do not actually have an oil pressure problem,then move forward with that knowledge.

 

[Matt69olds]

Before doing anything, look over the wiring harness around the back of the engine. Make sure nothing is damaged or rubbing on anything. The oil pressure wire is dark blue if I remember correctly.

More than likely the sending unit is starting to fail. Replacing it would be the easiest, and most probable way to solve the problem.

If the replacement sender has the same symptoms, next step would be to put a mechanical gauge on it. If the oil pressure is normal, then you have a wiring of actual gauge issue.

 

[JamesSam]

Before doing anything, look over the wiring harness around the back of the engine. Make sure nothing is damaged or rubbing on anything. The oil pressure wire is dark blue if I remember correctly.

More than likely the sending unit is starting to fail. Replacing it would be the easiest, and most probable way to solve the problem.

If the replacement sender has the same symptoms, next step would be to put a mechanical gauge on it. If the oil pressure is normal, then you have a wiring of actual gauge issue.

Yep. Today I checked the oil level(was good) and got under the truck , wiped away a little grime and oil drips. Then I unplugged the connector from the sending unit and plugged it back in.

The guage was maxed out before, and after unplugging and plugging back in the connector for the seding unit, the guage had reset to ~40 psi. All this before ignition obviously. I then took it for a ride and the guage seemed to stay in range, then about halfway through the trip, the guage started maxing out when coming to a stop or with no throttle. Once the gas is given, it perks right back in to range.
Level looking good:

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Sending unit looks to have some calcium or maybe acidic looking build up on it. Connections looked decent:

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Tomorrow, I will post pics of guage while maxed out at a stop, and then again while driving. I also will be looking for a sending unit at a parts place nearby or ordering one. If/when I switch out the sending unit I will post results.

 

[83Stepper]

I've always ran a mechanical gauge for as long as I can remember. For those with the electrical sender, it was usually just ripping out the electrical sending unit and just plumbing in a gauge on any non efi motor. Honestly it sounds as if the sending unit is starting to fail. Could be as simple as the unit is failing internally causing it to ground thus causing the gauge to peg at max.

 

[JamesSam]

So, since last posting, I purchased a new sending unit and installed it tonight. Install was while the sun was going down and I have to work in the driveway so lots of flashlights and no pics of the install or of the guage reading. The dash is very dimly lit on that side and test drive was nocturnal.

With the new sending unit installed, upon ignition, the needle in the guage moved around a bit and settled pretty much at 29 psi. While driving it barely moved between 26- 29 psi. It did respond slightly to some throttle but not much.

It is reading something and the needle does move some, and this new unit is not maxing out on the guage. I guess that is a positive. I plan to trouble shoot more soon. I wanted to get the new sending unit installed tonight, because it is going to rain until Friday.

The electrical node attachment from what I can see could use a good cleaning. I know oil can and does spritz in this general area near the sending unit. When the rain clears and I have a chance I will post more testing results and pics.

Old sending unit:

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[Long Rider]

Beware, China strikes again. I bought a replacement electric sending unit for one of my Squares and it read zero no matter what. So I bought another one and it wouldn't budge off 0 either. So I ordered one from parts Geek and it works. One out of three aint bad. Sounds like a song title, doncha think?