Oil pressure gauge all over the place.

[ramdough]

Had a scare. My oil pressure gauge was always very shaky, but was always centered around 40….. this weekend it started shaking lower and lower…. I checked the oil level and the light never came on. Now it is shaking around 80….. occasionally it would drop to below zero then bounce full scale.

My guess is I have a bad wire or sensor.

Anyone go through this?

Any debug hints?


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[GeneralDisorder]

Year and model?

 

[ramdough]

1999 1083A1


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[tennmogger]

Had this happen on an A0, 3116 engine, and it was a loose oil pressure sender where it screws into the block. The grounding to the block was intermittent.

 

[GeneralDisorder]

It does sound like a connection problem. But the 3126 and C7 both do have oil pump issues and the pumps for them have gone through a couple design changes so I would find out why it's reading funky and why it's bouncing when it does read. Not something you want to kick down the road on the HEUI engines.

 

[ramdough]

Had this happen on an A0, 3116 engine, and it was a loose oil pressure sender where it screws into the block. The grounding to the block was intermittent.

Where on the block is this sensor?


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[tennmogger]

Engine left (drivers) side, middle.

 

[TomTime]

Where on the block is this sensor?


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Mine did the same thing. Mine was actually the wire that went into the oil switch. Here are some pictures of where it's is located.





I removed mine, cleaned up the threads, and wires, fixed the wire, reinstalled and it works great now.

Good Luck,
Tom.

 

[Keith Knight]

What is proper oil pressure my 2003 3126B is always at 70psi.

 

[GeneralDisorder]

What is proper oil pressure my 2003 3126B is always at 70psi.

It's going to change with temperature and RPM...... Under what circumstances is yours reading 70?

If it always reads 70 under all conditions then something is wrong. That's probably a bad reading that's not reflecting reality.

The general rule is 10 psi per 1,000 RPM at a minimum.

Every pressure transducer on my 2008 has thrown up error codes and in the case of the oil pressure transducer it would sometimes read zero, and sometimes read pegged out. Also have got codes for the atmospheric pressure and boost pressure sensors. Ended up replacing all of them and the harness. These transducers don't last forever and when they do fail it can range from annoying check engine light, to limp mode with no boost, or squirting oil out of the electrical plug. Internally they have a diaphragm that operates a piezoresistive strain gauge. If the diaphragm ruptures due to age they can leak oil.

 

[TomTime]

Deleted.

 

[Keith Knight]

So always, at Highway speeds of 50-60 with high speed gears. I just went and checked with everything off it shows just under 40psi. But a lot of my gages don’t go to zero. Like the fuel tank is full and in off position it’s reads 3/4 full. Both air tank gages go from 120 to about 100 in the off position. Just figured that was all normal as it’s been this way for 8 years. But now I’m wondering if something is a little crazy.

 

[GeneralDisorder]

The off position isn't important as long as the gauge calibrates itself when you turn the ignition on. If it doesn't read zero with the ignition on and engine off then you need to investigate why.

Start it up and let it get to full operating temp on high idle and once the fans cycle a few times (if it's warm enough) then let it idle back and report what the hot idle oil pressure is.

 

[Keith Knight]

Hot idle is 60-65

 

[GeneralDisorder]

Hot idle is 60-65

Does the gauge zero itself when powered on? Because 60-65 is not a likely correct reading based on what I've seen on a lot of other trucks. Usually between 20 and 40.

 

[Keith Knight]

I never see the needle go to zero at any time.

 

[ramdough]

It's going to change with temperature and RPM...... Under what circumstances is yours reading 70?

If it always reads 70 under all conditions then something is wrong. That's probably a bad reading that's not reflecting reality.

The general rule is 10 psi per 1,000 RPM at a minimum.

Every pressure transducer on my 2008 has thrown up error codes and in the case of the oil pressure transducer it would sometimes read zero, and sometimes read pegged out. Also have got codes for the atmospheric pressure and boost pressure sensors. Ended up replacing all of them and the harness. These transducers don't last forever and when they do fail it can range from annoying check engine light, to limp mode with no boost, or squirting oil out of the electrical plug. Internally they have a diaphragm that operates a piezoresistive strain gauge. If the diaphragm ruptures due to age they can leak oil.

Is the recommendation to clean and reseat or replace as they are old?


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[Ronmar]

Is the recommendation to clean and reseat or replace as they are old?


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That would be my recommendation, as well as pulling the dash and confirming the connections to the back of the gauge as the sense sig goes thru a plug to get to screw terminals on the gauge itself. if it is a 2 wire sensor, you also need to confirm one of the wires indeed goes to ground, and that that ground does indeed return to the gauge ground..

 

[GeneralDisorder]

I never see the needle go to zero at any time.

Then something is broken. Probably the gauge considering it doesn't go to zero with power on/engine off.

Test oil pressure with a mechanical shop gauge and then fix/replace whatever is broken with the stock system to get it reading correctly.

 

[Ronmar]

I never see the needle go to zero at any time.

Well when you turn on the switch an accurate instrunment with 0 pressure applied should indeed read 0… That warm pressure sounds a little high. You could hook up a mechanical gauge to confirm its readings. They put a manifold on these trucks where the switch and gauge sender attach, so it is easy to plumb in a test gauge…