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post #1 of 8 Old 05-15-2013, 10:55 PM Thread Starter
rosco3059
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Oil pressure question

Hi all,

My 81 CJ7 4.2 I6 has been having some oil pressure issues. Upon start up, I am getting about 25 PSI and lose all the pressure after I begin driving. Anybody have a similar problem? I am contemplating replacing the oil pressure gauge but have not done so yet. Also of note is that I replaced the oil pump recently. However, I don't think I would get any pressure if was not primed properly. I have also not noticed any ticking or knocking in the motor.

John

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post #2 of 8 Old 05-16-2013, 03:12 AM
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Did you use a gasket between the oil pump and engine block mounting surface? Depending on the mating surfaces of both, sometimes you need a gasket and sometimes not. I had a similar problem last year on my I6 engine where pressure was good when engine was cold but dropped significantly once it warmed up. Dropped the pan and found I forgot to put in a gasket for the new oil pump but the original never had one that I recall. Anyway, once the gasket was in place, oil pressure stays the same whether its a cold or hot engine and I have about 20psi at idle and up to 70psi on the high.

A good feature is to add an additional Oil Pressure Gauge right at the engine block so you know what kind of pressure you have at a glance. I bought a small glycerin filled gauge from McMaster-Carr.com. The one in the photo is not liquid filled and was shortly changed out with one that is.


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post #3 of 8 Old 05-16-2013, 06:24 AM
Matt1981CJ7
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You may consider checking the tolerance between the pump gears and the pressure plate. Over time, the gears and plate will wear causing a drop in pressure.

Also, make sure the relief valve slides freely inside the housing.

Good luck,

Matt
Attached Thumbnails
OilPump1.jpg   OilPump4.jpg   OilPump3.jpg   OilPump2.jpg  


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post #4 of 8 Old 05-16-2013, 10:20 AM Thread Starter
rosco3059
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Excellent suggestions gents! I will check these two potential problems out.
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post #5 of 8 Old 05-16-2013, 08:08 PM Thread Starter
rosco3059
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Quote:
Originally Posted by keith460
Did you use a gasket between the oil pump and engine block mounting surface? Depending on the mating surfaces of both, sometimes you need a gasket and sometimes not. I had a similar problem last year on my I6 engine where pressure was good when engine was cold but dropped significantly once it warmed up. Dropped the pan and found I forgot to put in a gasket for the new oil pump but the original never had one that I recall. Anyway, once the gasket was in place, oil pressure stays the same whether its a cold or hot engine and I have about 20psi at idle and up to 70psi on the high.

A good feature is to add an additional Oil Pressure Gauge right at the engine block so you know what kind of pressure you have at a glance. I bought a small glycerin filled gauge from McMaster-Carr.com. The one in the photo is not liquid filled and was shortly changed out with one that is.
Keith,

Where did you attach?
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post #6 of 8 Old 05-16-2013, 08:44 PM
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Attach what? The pressure gauge?

Sent from my iPhone using JeepForum

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post #7 of 8 Old 05-16-2013, 09:22 PM Thread Starter
rosco3059
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Quote:
Originally Posted by keith460
Attach what? The pressure gauge?

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Yes, the pressure gauge
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post #8 of 8 Old 05-16-2013, 09:28 PM
keith460
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I had to remove the pipe fitting and drill and tap another 1/8 NPT for the gauge.

Used the existing pipe fitting as a pilot hole guide for centering while drilling. Then flipped the block around and finished drilling with the correct size drill for taping the 1/8" NPT.


Then tapped it to a 1/8" NPT.


Installed back in the engine block.

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