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Unread 08-31-2009, 10:22 PM   #1
ottovonmerz
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1983 CJ5 
 
Join Date: Aug 2009
Location: New Braunfels, Texas
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Oil Pump replacement question?

Hey Everyone!

New to the forum, but not to CJs.

My 83 CJ5 got a rear main leak again. Last time i replaced the rear main was in 97' so it's been awhile. While I had everything apart to change the rear main, I figured I might as well change the timing chain while I was there (98,000 original miles, and slack). My question is this:

should I go ahead and change the oil pump while I'm under there? The jeep has always had low pressure showing on the electric gauge (sender has been replaced). I know that the 258 had big oil passages, and I'm tempted while I'm doing all this to just plumb in a mechanical oil pressure gauge as well.

If a new oil pump is the recommendation, should I go stock replacement, high volume?

Any info would be greatly appreciated.

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Unread 09-01-2009, 03:42 PM   #2
JimNut
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1986 CJ7 
 
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I just finished installing a Melling High Volume oil pump in my 258 last night. I was replacing the RMS and since I lready had the oil pan off and the fact that I've had low oil pressure for sometime and figured it couldn't hurt. I know the engine is tired (all original with 180k) and I'm not ready to do a full rebuild yet. Hoping this might buy it some additional life. I'll post up the difference in oil pressure once I get the engine fired up again. Just dropped it back in the jeep last night.
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Unread 09-01-2009, 03:48 PM   #3
DT5150
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might as well while you're in there. they're not too expensive.
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Unread 09-01-2009, 06:40 PM   #4
ottovonmerz
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jimnut...

i'm eager to know if that melling helps. let me know!
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Unread 09-01-2009, 08:49 PM   #5
DUX4LIFE
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Quote:
Originally Posted by JimNut View Post
I just finished installing a Melling High Volume oil pump in my 258 last night. I was replacing the RMS and since I lready had the oil pan off and the fact that I've had low oil pressure for sometime and figured it couldn't hurt. I know the engine is tired (all original with 180k) and I'm not ready to do a full rebuild yet. Hoping this might buy it some additional life. I'll post up the difference in oil pressure once I get the engine fired up again. Just dropped it back in the jeep last night.
Did you get the one for the 4.2 or the 4.0 that was talked about a while back? I ordered the one for a 4.0 for my 258. Should be in tomorrow and I'll see if I want to figure out how to make it work in my 258.
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Unread 09-02-2009, 12:04 AM   #6
Rob55
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I am running the Mellings High Volume (brand new rebuild, about 500 miles) and it seems great - pressure is about 30 at idle, no problems.
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1984 CJ7, 258, MPI, 4.0 head, Borla, 700r4, amc20 (detroit), Dana 30 (OX), 4.56 gears, Warn Hubs, Dana 300 with 4:1, 4.5 RE lift with 1" body, Bilsteins, dual battery, PS, PB, full cage, two dogs in the back....
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Unread 09-02-2009, 02:33 AM   #7
Bubba Ray
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Jimnut, let us know how it turned out.
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Unread 09-02-2009, 07:31 AM   #8
JimNut
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Hope to have the jeep fired up in the next couple days. I had the engine out for some other reasons so I still need to hook everything back up. Just dropped the engine in Monday night.

Quote:
Originally Posted by DUX4LIFE View Post
Did you get the one for the 4.2 or the 4.0 that was talked about a while back? I ordered the one for a 4.0 for my 258. Should be in tomorrow and I'll see if I want to figure out how to make it work in my 258.
It lists that it is the correct one for a 4.2 however when I received the pump the pickup assembly that was supplied wouldn't clear my oil pan so I ended up using the original pickup. It was the correct depth but it would hit the front edge of the pan where it drops down. This is the pump that I ordered.

http://www.hdmaddog.com/AMC-Jeep-Hud...-p6843170.html
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Unread 09-02-2009, 09:25 PM   #9
ottovonmerz
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I went ahead and bit the bullet today and bought the melling high volume pump today. i figured better safe than sorry, and i sure as hell don't want to pull the pan down again. I'll keep everyone posted as to the results. Thanks to everyone for the input!
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Unread 09-08-2009, 11:42 AM   #10
JimNut
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I fired up the Jeep for the first time yesterday after installing the Melling high volume oil pump and WOW WHAT A DIFFERENCE! With the original oil pump after the engine was warmed up I would get around 7-10psi. With the Melling pump I'm at a constant 40-45psi @ idle and it jumps to around 60psi as soon as you touch the gas. Definitely worth the price in my book. Now if I could just get the oil pan/RMS to quit leaking
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Unread 09-08-2009, 12:42 PM   #11
shank38242
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And no one has issues with the high volume pump pumping the pan dry? I have heard on other applications that if you go with a high volume pump you need a bigger pan, is this not the case with the 258?
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Unread 09-09-2009, 12:10 AM   #12
ottovonmerz
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jimnut...that's awesome! just what i wanted to hear. just got the timing chain on tonight, and brought everything to tdc. gonna press in the pickup on the new pump tomorrow. Hopefully i'll have time to get her all together in the next week or so.

It's funny before i had kids, this is was probably a 4-5 hour job....my jeep has been in pieces in the garage for over a month. Good Times!
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