1990 Jeep Cherokee 4.0 Inline 6 with 5 speed transmission.

The old lady lives again. After 5 years of sitting and being pushed from spot to spot, she fired up today. Prior to starting, I replaced the front valve cover breather hose, rear valve cover PCV line, valve cover gasket, oil pan gasket, oil filter, oil drain plug, fresh oil, and some fresh premium gas. It's so good to have my Jeep running again.

Compression test shows 115, 120, 110, 120, 120, 110

But, with the good, comes the bad. Oil pressure on the gauge shows 60 at idle and goes up with throttle increase. I've been searching through multiple threads, but would like to ask you fine folks, any ideas what could be wrong? It's been a long time since I drove it, but I don't remember that being normal.

Thanks in advance for any and all help.

Dallas

 

I suppose you should verify that pressure with a mechanical gauge. I'll take a look and see if I can find anything on the pressure regulator....If it's really that high it might be putting some serious wear on things, Idk though.

 

All I could find is that max for a 2.5 is 75#. Was tinkling maybe your regulator gummed up or something sitting 5 years.

 

Note from DJ
I hope this information will help. I found it with a Google search:
https://www.cherokeeforum.com/f2/oil...roblem-201046/
Original Post was by JeepCherokeeJoe with a 2001 XJ
I changed the oil a few weeks ago. Right after the change I noticed the check gauges light turned on and the oil pressure dropped to zero. This problem had not happened before this. The engine runs perfectly and does not sound like there is low oil pressure, and it only drops to zero at idle. Can someone explain?
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Post #10 by Bobolink on 10-27-14
Nowhere do I see what year Cherokee you're referring to. If it's '90 or older, a Renix, then it's not a problem with the connector to the sending unit. I don't know about the '91 or newer, but the Renix gauge will read HIGHER with a bad connection. The more resistance at the connection, the higher the oil pressure reading. If you disconnect the wire completely from the sender, the gauge needle will peg all the way to the right, well above the 80 psi mark.

 

Thank you! I will take a look at the regulator and make sure it is in good working condition.

That is a great find! With the amount of oil all over this engine, i'm sure this connection is gummed up as well. I'll get it cleaned off, as well as the regulator inspection and report back.

Thanks again for your help. I love this community!

 

Most engines, in there somewhere is a spring holding a deal on the oil gallery that will bleed off excessive pressure. Slips me right now what it's called, and not even sure the 4.0 has one or where it is. (HELP someone!)(pressure relief valve?)

I went out and pulled the wire of my sender on my 90 Renix and the gauge shot way up past everything, as mentioned in DJ's link. (thanks DJ!)