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Unread 11-06-2009, 04:46 PM   #1
Flange
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1983 CJ7 
 
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304 Oil Pump - Need Help

Ok so I have a rebuilt 304 that runs and sounds great however the engine has high oil pressure. I have changed the sending unit twice and rewired the gauge. In addition I put a mechanical gauge on the engine and the pressure is still way up.

My next thought/hope is the oil pump is malfunctioning.

My questions are: if I replace or remove the oil pump do I need to repack the gears? Also, are those gears going to come falling out and if so how difficult are they to line back up with the distributor?

Any help on this would be greatly appreciated.

Thanks
Struggling newbie


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Unread 11-06-2009, 05:05 PM   #2
captdan
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I have a 304 built up and I run 40 as a low to 80psi when it's cold. I have a oil gauge that has a tube that runs up fromt he engine to a gauge and it measures the pressure. Is that the gauge you have? Hope this help....How high is your high pressure?
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Unread 11-06-2009, 05:27 PM   #3
h2ojeep
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Quote:
Originally Posted by Flange View Post

My next thought/hope is the oil pump is malfunctioning.


Is is possible that the bypass valve (I assume(almost sure) jeep has one) got stuck in the rebuild process?

I don't know if a high pressure pump is available for AMC engines, but did you by chance rebuild the pump with a high pressure pump? (common dilemma in SBC engines, when what was wanted was high volume not high pressure)
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Unread 11-06-2009, 05:33 PM   #4
Flange
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Quote:
Originally Posted by h2ojeep View Post
Is is possible that the bypass valve (I assume(almost sure) jeep has one) got stuck in the rebuild process?

I don't know if a high pressure pump is available for AMC engines, but did you by chance rebuild the pump with a high pressure pump? (common dilemma in SBC engines, when what was wanted was high volume not high pressure)
Thanks for the reply. My answer is I dont know. The only new pump I could find came from 4 wheel drive hardware so no rebuild was needed. Dont know if it is a high pressure pump thou. Something I will look into.
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Unread 11-06-2009, 05:53 PM   #5
kappa505
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I have a rebuilt 304 that runs high also. Cold it is anywhere between 65-80 psi. Once it warms up anywhere between 8-15 psi. It depends on what weight oil I am running.
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Unread 11-07-2009, 06:02 AM   #6
bigirons79CJ5
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The gears will fall out pretty easily when the cover is removed, but they are very simple to work on and to get realigned when you install them.
To get the oil pump to prime after replacing or rebuilding, I use a small clear tube(about 2-3 feet in length) full of motor oil. I stick the tube in the center hole were the oil filter screws on and use a little bit of compressed air to blow the oil from the tube into the gears of the oil pump. Then screw your filter back on and start. Sometimes it took two tubes of oil to get it primed.

After my rebuild a little over a year ago, I have the same problem. High oil pressure. My pressures run about the same as everyone elses on here. I fought with leakage issues for a while and finally got them under control. I installed the polished aluminum valve covers that don't have holes cut in for breathers. I've been pondering the idea of drilling one or both out and installing a breather. The reason I'm thinking of installing a breather is that I have some oil getting blown out of my dipstick tube. Does anyone think it'll solve my problem?
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Unread 11-07-2009, 06:08 AM   #7
kappa505
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I have that problem with the dipstick, and from what I have read it may be solved with replacing the PCV that is clogged or broken. I just haven't gotten around to it with mine.
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"Nothing in the world can take the place of Persistence. Talent will not; nothing is more common than unsuccessful men with talent. Genius will not; unrewarded genius is almost a proverb. Education will not; the world is full of educated derelicts. Persistence and determination alone are omnipotent. The slogan 'Press On' has solved and always will solve the problems of the human race." Supposedly President Coolidge
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Unread 11-07-2009, 06:17 AM   #8
Flange
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Quote:
Originally Posted by bigirons79CJ5 View Post
The gears will fall out pretty easily when the cover is removed, but they are very simple to work on and to get realigned when you install them.
To get the oil pump to prime after replacing or rebuilding, I use a small clear tube(about 2-3 feet in length) full of motor oil. I stick the tube in the center hole were the oil filter screws on and use a little bit of compressed air to blow the oil from the tube into the gears of the oil pump. Then screw your filter back on and start. Sometimes it took two tubes of oil to get it primed.

After my rebuild a little over a year ago, I have the same problem. High oil pressure. My pressures run about the same as everyone elses on here. I fought with leakage issues for a while and finally got them under control. I installed the polished aluminum valve covers that don't have holes cut in for breathers. I've been pondering the idea of drilling one or both out and installing a breather. The reason I'm thinking of installing a breather is that I have some oil getting blown out of my dipstick tube. Does anyone think it'll solve my problem?
Thanks for the response and thats a great looking 304! So I just want to be sure...even if I remove the current pump to inspect for issues I will need to reprime it if I put that pump back on? Or is it that I only need to prime a new pump if I deceide to replace the current one?

BTW I installed the same valve covers on my 304. Let me know if setting up a breather system helps with your oil PSI. Maybe I will go the same route.

Thanks in advace for the help.
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Unread 11-07-2009, 07:00 AM   #9
JeepHammer
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AMC V-8 pumps fall out in your hand with little to no work.
Taking one out isn't an issue, getting it back in correctly is usually the 'Problem'...

What I want to know is why you haven't reported the 'High Pressure' reading...

With 10W40 or 15W40 oil you can EASILY reach 'High' oil pressures when you start up,
Mine often reads 80+ PSI on startup...
Nothing wrong with that if you don't have a breaker points distributor (and '83 does NOT)...

You get above 100 or 120 PSI, then you might have some issues with the oil filter housing, they like to give way at the seam about 110 or 120 PSI, and I've seen them separate the canister from the base about the same pressure...

After changing to a filter that COULD take the pressure, we ran oil pressures up to 140-150 pretty regularly.
At around 150-160 we started to get oil leaks past stock type seals, so instead of trying to seal up past that pressure,
We simply limited the pressure at about 140 PSI or so, and never had any issues with the engines, and the AMC V-8's LOVED the extra oil that was delivered.

If you are below 100 PSI (Gaged on a decent gauge) at the top end of your pressure run, then consider yourself a lucky man to have oil pressure at all!

How about telling us what the top end pressure was (When gaged on a mechanical gague)?
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Unread 11-07-2009, 08:52 AM   #10
Flange
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Quote:
Originally Posted by JeepHammer View Post
AMC V-8 pumps fall out in your hand with little to no work.
Taking one out isn't an issue, getting it back in correctly is usually the 'Problem'...

What I want to know is why you haven't reported the 'High Pressure' reading...

With 10W40 or 15W40 oil you can EASILY reach 'High' oil pressures when you start up,
Mine often reads 80+ PSI on startup...
Nothing wrong with that if you don't have a breaker points distributor (and '83 does NOT)...

You get above 100 or 120 PSI, then you might have some issues with the oil filter housing, they like to give way at the seam about 110 or 120 PSI, and I've seen them separate the canister from the base about the same pressure...

After changing to a filter that COULD take the pressure, we ran oil pressures up to 140-150 pretty regularly.
At around 150-160 we started to get oil leaks past stock type seals, so instead of trying to seal up past that pressure,
We simply limited the pressure at about 140 PSI or so, and never had any issues with the engines, and the AMC V-8's LOVED the extra oil that was delivered.

If you are below 100 PSI (Gaged on a decent gauge) at the top end of your pressure run, then consider yourself a lucky man to have oil pressure at all!

How about telling us what the top end pressure was (When gaged on a mechanical gague)?

Thanks jeephammer for the help.

The gage that I put on my jeep is an aftermarket gauge that reads up to 100. It is currently pined at 100 when the jeep is running. I had a mechanic put a mechanical gage to test the pressure and it hit 120. Thus leading me to believe that there is an oil pressure issue no a gauge problem.

What I dont understand is during the break-in period the pressure was fine and now its running very high. The oil running is 10w-30...

The troubleshooting that I have done is as follows:

-Changed the oil filter

-Cut the relief valve spring ˝ inch

-Changed the sending unit and gauge

And I the pressure still remains high. The fortunate part (if there is one) is I have not experienced any other issues such as blowing the filter or oil cap off and there doesn’t seem to be any leaks.

Do you think changing the oil would help? Should I try to tackle replacing the pump? I am truly at a loss on how to proceed further.

Thanks for the help.
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Unread 11-07-2009, 01:19 PM   #11
Flange
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Quote:
Originally Posted by Flange View Post
Thanks jeephammer for the help.

The gage that I put on my jeep is an aftermarket gauge that reads up to 100. It is currently pined at 100 when the jeep is running. I had a mechanic put a mechanical gage to test the pressure and it hit 120. Thus leading me to believe that there is an oil pressure issue no a gauge problem.

What I dont understand is during the break-in period the pressure was fine and now its running very high. The oil running is 10w-30...

The troubleshooting that I have done is as follows:

-Changed the oil filter

-Cut the relief valve spring ˝ inch

-Changed the sending unit and gauge

And I the pressure still remains high. The fortunate part (if there is one) is I have not experienced any other issues such as blowing the filter or oil cap off and there doesn’t seem to be any leaks.

Do you think changing the oil would help? Should I try to tackle replacing the pump? I am truly at a loss on how to proceed further.

Thanks for the help.

If I need to replace the pump difficult is it to line up the gears for the pump once they come out of the timing cover?
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Unread 11-07-2009, 04:05 PM   #12
bigirons79CJ5
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New or old, the pump will need to be primed. Putting oil in like I said is to get the gears saturated with oil so they will prime and will draw in the new oil. The oil pump is nothing more than two gears meshed together. It's kind of like a roots style blower. You're problem with high oil psi is more than likely, not your oil pump, so if I were you I would leave it alone. Unless your like me and want some practice and want to know what the gears look like. One gear is long and one is short.
Melling Oil Pump Gear Kit V8 and Other Jeep Parts and Jeep Accessories by 4 Wheel Drive Hardware
The long gear has a slot in it that the dizzy fits in. I've never had a problem with taking mine in or out.
__________________
79 CJ5 4" Skyjacker
35" Dunlop MT's, 9000lb Warn
304 built with Edelbrock cam,valve springs,timing set,intake,Holley truck avenger carb, DUI ignition, fenderwell headers w/Supertrapps, Twin Sticked D20
FOR MORE PICTURES, CHECK OUT MY PHOTOBUCKET
http://s999.photobucket.com/albums/af118/bigirons79cj5/
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Unread 11-08-2009, 07:37 AM   #13
JeepHammer
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When you rebuild the pump, since the block oil system isn't dry,
Just gob in a handful of petroleum Jelly or break in lube.
Since the engine bearings are NOT dry, you don't have to prime the engine...

The 'Goop' in the pump will make for suction VERY quickly and protect the pump for the one or two seconds it will run before oil gets there.

What I would do is take the filter head off the pump, and check the bypass valve.
That pressure bypass valve needs to open to let excessive pressure off, and it sounds like it's not working.

When you take the filter head off, your oil pump impellers can fall directly out of the pump hosing, so be prepared to catch them.

Oil pump impellers are NOT timed, you can put them in any which way,
Just make sure the one with the long shaft engages the distributor shaft before you try and install the floor plate/filter head again!

I've never heard of a production pump producing 120+ pounds of pressure,
and if it's true, your distributor drive gear on the camshaft won't live long with that kind of resistance against it.

Again, I urge you to get a hand held gauge, thread into the sending unit port, and get an actual reading...

120 PSI should have split your filter wide open,
And that is what makes me wonder about the voracity of your "mechanic's" claim he put a mechanical gauge on it and it read 120 PSI...

SO!.
Let's start at the filter,
Just above the filter there should be the 'Filter Head'.
That filter head has a bypass valve in it.

Normally, when the filter gets clogged, that bypass valve is supposed to bypass the filter to get oil into the engine.
When enough back pressure builds up, (Resistance from a clogged filter),
A preset spring pressure is overcome, and the oil is allowed to circulate in the engine...
Bypassing the filter.
It's a 'Fail Safe' system if the filter decomposes or gets clogged, oil can bypass the filter and reach the engine.
(Dirty oil is better than NO OIL!, that's why the call it a 'Fail Safe', even if the filter fails, the engine is still saved)

I don't know how that valve would fail to give you 100+ PSI oil pressure, but it's a place to start!
-------------------------------------------------

The only way I can think of for your oil pressure to be reaching 100+ psi is for a main feed to the engine to be BLOCKED,
And that would mean the engine isn't getting ANY oil volume.

The AMC V-8 is basically one HUGE leak from a thousand tiny holes...
The block is like those garden hoses you water with, they are punched full of little holes all the way down their length...

Front cam bearing should be changed ANYTIME you have the front cover off,
Since the timing chain, fuel pump eccentric and distributor all load the front bearing, it wears out VERY quickly...

Then you have camshaft bearings that run continuously,
Then there are the lifter bores that are constant sources of volume/pressure loss.

When you get into the bottom of the engine, there are rods and mains that drool like mad dogs in heat!
We all know about the loss of pressure to the back of the AMC V-8 blocks,
And lack of volume from all the 'Leaks' is the reason why!

AMC V-8 blocks aren't like SBC blocks, you can't connect directly into the gallery plugs at the front end of the block and run a pre-oiler to the internal oil pump...
Because AMC's have a front cover that holds the distributor/pre-oiler that has to be off the engine to access the front gallery plugs,
AND, AMC's don't have an internal oil pump!
(and people wonder why I install a second gauge in the BACK of the block when they are down for machining! So you can see what's happening at the END of all those 'Leaks' in the engine!)

I don't know how the bypass valve would fail to cause 100+ PSI...
But it's a place to start.

Remember!
1. Since the filter didn't split at the 'Gauged' 120 PSI, and should have,
I would get a mechanical gauge, and plug it into the oil pressure gauge line fitting and check for myself...
I've never seen ANY filter that would take 120 PSI, and I've blown quite a few up with these racing engine oil pumps...
If you didn't see the guy do it with your own eyes, then do the test for yourself...

2. When you take the filter head/floor plate off the pump, the Impellers WILL fall out in your hand, so be ready for that!
Also, you need to 'Dry Fit' the impellers in the housing using 'Plasti-Gauge'.
Good rebuild kits will come with two or more thickness gaskets, start with the thick one and work down until you find the gasket that gives you the best fit,
And use Plasti-Gauge under BOTH impellers, they are often different thicknesses!

3. Good rebuild kits come with bypass valve spring & plunger/piston.
If you don't get one, you will have to track one down that DOES have the bypass rebuild kit.

4. When you have figured out which gasket to use (DO NOT stack gaskets!),
Don't forget to pack the impellers/housing with Vasoline or assembly lube so the impellers don't DRY START.
DO NOT USE GREASE!,
Vasoline or assembly lube will dissolve in oil, where grease chunks can clog small oil passages and build up gunk in the engine.

This is from the link someone posted, and it's got the bypass spring and plunger in the middle...
BUT I ONLY SEE ONE GASKET...?


Last edited by JeepHammer; 11-08-2009 at 07:52 AM..
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Unread 11-08-2009, 08:02 AM   #14
Flange
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Thanks Jeephammer for this great information. I really appreciate all the time you took in replying to my post.

First thing I will do is get a mechanical gauge on the engine so I can view the true pressure first hand. Second, if the pressure is truly 100+ psi I will inspect the bypass valve and replace the oil pump cover. Once thats done I will recheck with the mechanical gauge.

Thanks again for the help and I will keep you updated
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