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Unread 10-19-2013, 04:25 PM   #1
325INFREGT
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1976 CJ7 
 
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Low oil pressure AMC 304

Just today heard the lifter clacking and lost oil pressure. I looked under the hood and there is oil coming out of the oil pump. Not spewing or anything like that but it definitely leaks. I've read through some other threads and they are talking about having to rebuild the engine because of cam bearings. I don't know enough to check that stuff out. I do know I don't want to have to replace the engine. It was running fine and this just happened today. How do I know whether I need to rebuild the oil pump or if I need an new engine. Up until this time it was at 20 psi at idle and 50-60 at highway speeds, which is about right. Any ideas? pretty bummed...

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Unread 10-19-2013, 05:07 PM   #2
325INFREGT
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Just looked up oil pump rebuild kits. Looks like you just drop the plate that holds the oil filter and out comes the old gears and spring. Wipe clean the inside housing, rub it with emory cloth and put in the new gears. Is that about all? Am I missing anything? Should I order the ones from bulltear or can I just get them from auto zone? Any help would be appreciated.
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Unread 10-20-2013, 06:10 AM   #3
325INFREGT
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Rebuilding it this morning. Pics to follow. Hopefully the gap between the gears and the housing meets specs, NOT interested in pulling the timing chain cover to fix this. If I have to do that, can you just pull the radiator and get the housing off or do you have to pull the whole engine?

c'mon jeep forum, help a brother out...

Thanks in advance
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Unread 10-20-2013, 07:52 AM   #4
davbytrace
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You dont have to pull the radiator (it will make the job easier), but you do have to disconnect it from the water pump. Basically, you have to disassemble everything hooked to the timing cover.

A couple of hints here:

1) Bump the engine to get the distributor rotor to the #1 position while confirming that the engine is at TDC on the timing cover, then mark the rotor position on the distributor.

2) Take lots of pictures while disassembling.

3) keep close track of what bolts go where. The alternator, water pump, timing cover, and power steering bolts are all different and are used in concert with each other to hold it all together.

4) Chase all the bolt threads with a die and clean all bolt holes with a tap. Replace any bolts that are questionable.

5) That timing cover is aluminum and can crack if mishandled or over tightened, but it must sit square and flat to ensure that the distributor gear seats correctly. Be sure to clean the gasket contact surfaces to a pristine condition on the block, timing cover, and water pump. Invest some time in this effort. Torque to spec.

6) Finally, the timing cover has two alignment pins built in. They are there for a reason. When you remove the cover, they may remain in the block or come out with the timing cover. They are simple roll pins, but they are essential for ensuring that the distributor gear aligns correctly on the cam gear. When you remove the cover, look for the pins. If they are not there, chances are they have been pushed into the timing cover by previous work. They will need to be reset.
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Unread 10-20-2013, 03:01 PM   #5
325INFREGT
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Thanks for your response. Very informative. I rebuilt the oil pump and cleaned out the oil pan. Nothing in the pan. No sludge or metal shavings. All clean. I rebuilt the oil pump and tightened the bolts for the timing cover. Put everything back together and the thing wouldn't start. Luckily I had bench tested the starter while I had the oil pan down and I have just recently replaced the battery so I knew it was the solenoid. Trip to autozone and 20 mins later fired right up. Hung out at 60 PSI oil pressure for a while. Drove it home and now it hangs out at idle at around 20 PSI and goes up to around 60 when accelerating. Haven't had it out on the highway yet, but I think I may have it licked.

Again, thanks for your response. After reading through what you had to say, along with some other research and a you tube video or two, I think I could have replaced the timing cover if I needed to. I still may have to, we'll see.

Appreciate it brother.
img_1561.jpg   img_1562.jpg  
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Unread 10-20-2013, 05:44 PM   #6
325INFREGT
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davbytrace,

Been driving it around this afternoon feeling good about myself. Oil pan leaks under pressure. Not a big deal, I can fix that. Noticed that under acceleration, especially from the halt, pressure builds to around 70 psi. That's a little high. Is it because of the new gears? Is it a big deal? It still drops to around 20 (18 in gear 22 in neutral or park) at idle, so that's good. I don't feel like it's a big issue.
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Unread 10-20-2013, 06:00 PM   #7
82JeepCJ7
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Get the little plastic nub that goes in the hole on the oil pick up screen. That prevents the pickup from sticking to the bottom of the pan.

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Unread 10-20-2013, 06:06 PM   #8
82JeepCJ7
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My Dad has a 1972 CJ5 with a 304 in it. The oil pressure was non existent in the motor. We installed a new mechanical gauge to make sure. First we put in a mid plate, thinking the clearance between the ends of the gears was excessive. That did not "fix" the issue. So, we ordered a oil pump rebuild kit that included new gears, bypass spring and plunger. The clearances with the new gears was so much tighter. The bypass spring was also stiffer. Now the engine has 50psi on start up and idles just under 20psi when warmed up.
img_2354.jpg

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Unread 10-21-2013, 07:10 AM   #9
325INFREGT
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Quote:
Originally Posted by 82JeepCJ7
Get the little plastic nub that goes in the hole on the oil pick up screen. That prevents the pickup from sticking to the bottom of the pan.
Where do I pick that up?
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Unread 10-21-2013, 05:22 PM   #10
82JeepCJ7
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It's easier to do something yourself than find one of them.

Just do something like this.

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Unread 10-21-2013, 05:29 PM   #11
82JeepCJ7
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Unread 10-21-2013, 05:45 PM   #12
davbytrace
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325INFREGT,

Pressure is resistance to flow, which is typically created by the tolerances in the things that oil goes to, such as main and cam bearings; and is affected by the viscosity of the oil which is dependent on weight, the amount of run time (breakdown), and temperature of the oil.

The idle pressure seems a little low and the running pressure seems a little high.

But in the big scheme of things, oil pressure seems to be OK considering the following: new pump internals and your gauges. Assuming that you have electric gauges, the combination of sender accuracy, resistance in wire connections, and gauge accuracy can easily provide an as-read error as much as 20%.

Just run the thing normally for a few hundred miles and break in the new pump. Keep an eye on the pressures over time and see how they behave given a reasonably equal operating temperature. Change your oil after about a hundred miles to make sure that any oil pump "wearing in" issues don't end up collecting in the oil pan or in the engine galleries.
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Unread 10-21-2013, 05:51 PM   #13
Krum81
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When you heard the lifters was your oil low?

Ive done some research and it seems these amc motors run around the oil psi's you are speaking of.

I know my AMC 360 sits around 20 idle and jumps to 40ish at driving speeds
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Unread 10-21-2013, 07:00 PM   #14
325INFREGT
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Quote:
Originally Posted by davbytrace View Post
325INFREGT,

Pressure is resistance to flow, which is typically created by the tolerances in the things that oil goes to, such as main and cam bearings; and is affected by the viscosity of the oil which is dependent on weight, the amount of run time (breakdown), and temperature of the oil.

The idle pressure seems a little low and the running pressure seems a little high.

But in the big scheme of things, oil pressure seems to be OK considering the following: new pump internals and your gauges. Assuming that you have electric gauges, the combination of sender accuracy, resistance in wire connections, and gauge accuracy can easily provide an as-read error as much as 20%.

Just run the thing normally for a few hundred miles and break in the new pump. Keep an eye on the pressures over time and see how they behave given a reasonably equal operating temperature. Change your oil after about a hundred miles to make sure that any oil pump "wearing in" issues don't end up collecting in the oil pan or in the engine galleries.
Quote:
Originally Posted by Krum81 View Post
When you heard the lifters was your oil low?

Ive done some research and it seems these amc motors run around the oil psi's you are speaking of.

I know my AMC 360 sits around 20 idle and jumps to 40ish at driving speeds
davbytrace

Thanks for the advice. I think you're right. I'll just keep an eye on it.

Krum81,

When I heard the lifters the pressure had gone way down. The psi that I was talking about was after the oil pump rebuild.
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