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Unread 03-11-2013, 08:07 AM   #1
lsukevinc
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1979 CJ5 
 
Join Date: Mar 2009
Location: Geismar, Louisiana
Posts: 289
304 oil pressure question

I had to replace my cam and lifters last year. I packed the oil pump with Vasoline to prime the oil pump. Ever since I did this last year, the gauge shows 40 psi at idle and maxes out while driving down the road.

This weekend I had to change my rear main seal and oil pan gasket. I knew my oil pump pick up was going to be dry when I started the engine up after everything was done.
I sat in the seat and watched the oil pressure gauge when I started it after the seal job was done. I knew the pressure would be low, so I wanted to see how low it was when it started and ran for the first few seconds. It seemed that it was at 20 when it was really dry, then after 3 or 4 seconds it jumped up to 40 psi. I took it for a spin around the block and it was the same again, 40 psi at idle and maxed out under normal driving speed. I have a few questions. Can the gauge be calibrated? It seems to be the stock gauge that came with the 79 AMC 304. Could it be a bad gauge or sending unit? Any help is much appreciated.

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Unread 03-11-2013, 10:06 AM   #2
82JeepCJ7
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1982 CJ7 
 
Join Date: Jun 2010
Location: Marysville, WA
Posts: 4,661
I am thinking faulty gauge, sending unit, or wires. Another reason why I only run mechanical gauges.

You can always pick up a mechanical gauge and hook it up to the block in place of the sending unit, never installing the gauge in the dash. Just sit it on the fender to test your motor. If it test shows good oil pressure, then you know the gauge circuit is faulty. If not, its in the motor. Cheap easy way to eliminate a few things.
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Unread 03-11-2013, 12:07 PM   #3
lsukevinc
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1979 CJ5 
 
Join Date: Mar 2009
Location: Geismar, Louisiana
Posts: 289
any idea on what brand gauge might be able to hook of to the engine in lieu of the sending unit?
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Unread 03-11-2013, 12:27 PM   #4
OleBlue73
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1973 CJ5 
 
Join Date: Oct 2009
Location: , Tennessee
Posts: 410
Quote:
Originally Posted by lsukevinc
any idea on what brand gauge might be able to hook of to the engine in lieu of the sending unit?
Just plumb it up to the same hole in the block the sending unit uses. Something like this. Sunpro, autometer and others make mech guages


image-1012113146.jpg

As 82JeepCJ7 does, I use a mechanical gauge in my dash. I have 1/8" copper tubing running from the fitting at the block to the gauge in the dash. Oil travels up the tubing to be read on the gauge.
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1973 CJ5, 304, T15, D20
2009 JKU, Rubicon
2005 TJ, X, 4.0, 6 speed
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Unread 04-02-2013, 02:23 PM   #5
lsukevinc
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1979 CJ5 
 
Join Date: Mar 2009
Location: Geismar, Louisiana
Posts: 289
i did replace it with a cheap mechanical gauge for now. once it warms up it seems for be normal. 10 psi at idle and 10 more psi per 1000 rpms.
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