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Posted: 1/9/2005 10:22:09 AM EDT
This has to do with the oil pressure gauge.

I have a 1995 Jeep Cherokee with about 130K on it. It has been a great car and that is the reason I am still driving it instead of trading it in after three years like I normally do..

Today I went to the rifle range and noticed that the oil pressure gauge was mostly pegging out on the high side. At idle speeds and lower speeds it seemed OK. However, it would go a little haywire whenever I would get up to highway speed. It has never done this before. The engine temperature was normal.

Does this sound like a gauge problem or an oil pump problem? If the oil pressure is on the high end is that really a problem that needs to be taken care of immediately?

What is you advice?
Link Posted: 1/9/2005 11:16:16 AM EDT
probably the oil pressure sensor
Link Posted: 1/9/2005 11:19:58 AM EDT

Originally Posted By fredshort:
probably the oil pressure sensor



+1
Link Posted: 1/9/2005 11:29:19 AM EDT
10-4 on the sensor
Link Posted: 1/9/2005 11:29:38 AM EDT
Probably sending unit. But it could in theory have spun a main bearing blocking oil flow to the crank which would send oil pressure sky high............but you would soon know it as catastrophic engine failure would soon occur.
Link Posted: 1/9/2005 11:36:42 AM EDT
[Last Edit: 1/9/2005 11:40:08 AM EDT by Pthfndr]
Probably the oil pressure sending unit. But you should go rent yourself a mechanical gauge, take off the sending unit and attach the gauge hose there, then verify the actual oil pressure at idle and higher rpm. If the pressure IS excessively high at higher rpm it could be a spun bearing or other restriction in one of the oil passages - bad news. It could also be a filter problem - when did you laast change the oil and filter? The other possiblity is a stuck pressure relief valve that at the low volume seen at idle doesn't cause an issue, but at higher rpm pump output causes enough restriction to raise the pressure. Excessive pressure can cause it's own problems.

The oil pump itself is not a concern here. It is apparently doing it's job.

One other thing to check is for a loose connection at the sending unit or else where in the harness. I've seen this many times on the line of vehicles I work on. At higher rpm the engine vibration/harmonics is just right to cause the loose connction at the sending unit to make almost no contact. On sending units, typically high electrical resistance gives a higher reading on the gauge, low resistance gives a low or zero reading on the gauge.
Link Posted: 1/9/2005 12:41:48 PM EDT

Originally Posted By Pthfndr:
Probably the oil pressure sending unit. But you should go rent yourself a mechanical gauge, take off the sending unit and attach the gauge hose there, then verify the actual oil pressure at idle and higher rpm. If the pressure IS excessively high at higher rpm it could be a spun bearing or other restriction in one of the oil passages - bad news. It could also be a filter problem - when did you laast change the oil and filter? The other possiblity is a stuck pressure relief valve that at the low volume seen at idle doesn't cause an issue, but at higher rpm pump output causes enough restriction to raise the pressure. Excessive pressure can cause it's own problems.

The oil pump itself is not a concern here. It is apparently doing it's job.

One other thing to check is for a loose connection at the sending unit or else where in the harness. I've seen this many times on the line of vehicles I work on. At higher rpm the engine vibration/harmonics is just right to cause the loose connction at the sending unit to make almost no contact. On sending units, typically high electrical resistance gives a higher reading on the gauge, low resistance gives a low or zero reading on the gauge.



I change the oil at every 3K so I don't think that is the problem.

Thanks for the info.
Link Posted: 1/9/2005 1:18:03 PM EDT
[Last Edit: 1/9/2005 1:19:29 PM EDT by Redcap]

Originally Posted By Flash66:

Originally Posted By Pthfndr:
Probably the oil pressure sending unit. But you should go rent yourself a mechanical gauge, take off the sending unit and attach the gauge hose there, then verify the actual oil pressure at idle and higher rpm. If the pressure IS excessively high at higher rpm it could be a spun bearing or other restriction in one of the oil passages - bad news. It could also be a filter problem - when did you laast change the oil and filter? The other possiblity is a stuck pressure relief valve that at the low volume seen at idle doesn't cause an issue, but at higher rpm pump output causes enough restriction to raise the pressure. Excessive pressure can cause it's own problems.

The oil pump itself is not a concern here. It is apparently doing it's job.

One other thing to check is for a loose connection at the sending unit or else where in the harness. I've seen this many times on the line of vehicles I work on. At higher rpm the engine vibration/harmonics is just right to cause the loose connction at the sending unit to make almost no contact. On sending units, typically high electrical resistance gives a higher reading on the gauge, low resistance gives a low or zero reading on the gauge.



I change the oil at every 3K so I don't think that is the problem.

Thanks for the info.



What the fuck does that matter?
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