No oil pressure on hot start up

J

Jester of Atlas

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Lancaster Pa
To start this off I replaced the oil pressure sensor with a mopar one a few months ago and problem still is present. 2002 tj automatic with 4.0

If I start my Jeep when it’s cold gauge instantly reads and is fine. Oil pressure reads fine when vehicle is warm and running. However, if the vehicle is warm and I shut it off to run into a store and I come back out when I start it the gauge shows zero and the check gauge light comes on. When you give it a little rev that gauge instantly raises in pressure to where it should be. The previous owner also had this issue but he through a knock off sending unit in it so I put a mopar one in as soon as I bought it, but the problem persists. any ideas? I haven’t found anything online with Google other than people saying to replace the sending unit.
 
Have you unscrewed the oil pressure sender and tested with a manual gauge?

Need to determine if you have a sensor issue or an actual oil pressure issue.

-Mac
 
Heat and electrical resistance go hand in hand. As temperature rises, so does electrical resistance.

It could be possible your sending wire is frayed in the sheath somewhere between the sender and the ECM causing a decrease in the cross-sectional area. If it gets to hot (say from heat soaking after you turn the Jeep off as you mentioned) it could be enough to cause a false reading.

However, @macleanflood has the right initial approach of testing with a manual gauge.
 
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Any update on this? I'm having the same issue upon a hot (210F) start. I can alleviate it by revving the engine to 2,000 momentarily for it to climb up to 20-40, where it stays most of the time. I'd swear it is an electrical issue.
 
CODE5 said:
Any update on this? I'm having the same issue upon a hot (210F) start. I can alleviate it by revving the engine to 2,000 momentarily for it to climb up to 20-40, where it stays most of the time. I'd swear it is an electrical issue.
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Nothing but I’m the exact same as you. I highly doubt it’s a mechanical issue.
 
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