Help! 1999 Jeep Cherokee Sport 4.0 Engine Rebuild Low Oil Pressure - JeepForum.com

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post #1 of 26 Old 09-30-2013, 05:36 AM Thread Starter
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post #2 of 26 Old 09-30-2013, 06:30 AM
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Did you replace the oil pump during rebuild?
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post #3 of 26 Old 09-30-2013, 06:40 AM Thread Starter
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post #4 of 26 Old 09-30-2013, 07:44 AM
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So what were the results of the mechanical gauge you said you were going to run? I'm willing to bet your pressures are just fine. My 97 TJ used to do the same thing. The oil pressure sending unit and dash gauge are known to be terribly inaccurate.

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post #5 of 26 Old 09-30-2013, 07:59 AM Thread Starter
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post #6 of 26 Old 09-30-2013, 08:27 AM
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Originally Posted by PilotPat24 View Post
I didn't check it with the mechanical guage yet. I'm going to do it this afternoon when I get home from work.

I just find it wierd that the guage read much higher prior to the rebuild...

Also, what makes the "check guages" light go on? is that from the sensor or from the actual guage on the dash? The check guage light went on when the guage on the dash dropped to zero...
The PCM puts the light on, based on voltage inputs from the oil pressure sensor.
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post #7 of 26 Old 09-30-2013, 08:37 AM Thread Starter
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post #8 of 26 Old 09-30-2013, 09:23 AM
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Originally Posted by PilotPat24 View Post
Could a bad ground cause an inaccurate reading

There is no seperate, external, ground for the Oil Pressure Sensor. But, if the connector pin sockets are corroded or damaged in any way it may have an affect on the sensor inputs to the PCM

or the fact that there are two wire harneess connectors not plugged into the a/c components since I removed them?
The AC electrical system won't affect the oil pressure sensor inputs to the PCM.
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post #9 of 26 Old 09-30-2013, 09:34 AM
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Yes, there was a new oil pump installed. It was an enginetech pump. Before putting the engine into the truck. I primed the oil pump and there was goof flow coming out of the oil filter hole. I then tightened up the oil filter to continue priming the oil and the drill wound up stopping when the pressure built up.

I sent the block out to a machine shop. Standard rod/main beraings and .020on the cylinders. They pressure checked the block and that came back fine.

Another thing worth mentioning is that the engine oil is very clean. It's not dirty at all.
The reason I asked about the oil pump was you said "when we were driving and we were making a left turn, the engine was idling and the psi went to around 15 directly to 0psi."

When you installed the oil pump was the pickup tube securly installed in the pump body? Did you install a gasket between the pump and the block, and torque the attach bolts down? Was the oil pump flush with the block at its mount point when it was securely installed?

You also said "continue priming the oil and the drill wound up stopping when the pressure built up." What drill motor did you use? I used a 120 volt/7.0 amp drill motor and it didn't stop. It slowed down some when the pump started pumping but it didn't 'stop'.

You did install a standard flow oil pump didn't you?
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post #10 of 26 Old 09-30-2013, 10:25 AM Thread Starter
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post #11 of 26 Old 09-30-2013, 04:45 PM Thread Starter
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post #12 of 26 Old 10-01-2013, 04:53 AM Thread Starter
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post #13 of 26 Old 10-01-2013, 05:27 AM Thread Starter
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post #14 of 26 Old 10-01-2013, 05:48 AM
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Quote:
Originally Posted by PilotPat24 View Post
Also worth mentioning is that there is a Fram oil filter on the engine.
Ditch it and put a Wix on it.

If you own a Renix Jeep, you'll want to check this out.

An index to over 30 write-ups can be found in the link below

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My Jeep Technical Photos

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post #15 of 26 Old 10-01-2013, 08:12 AM Thread Starter
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