304 Oil system/pressure issues - JeepForum.com
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post #1 of 18 Old 05-01-2013, 02:07 PM Thread Starter
st3dnut
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304 Oil system/pressure issues

The title explains it al. I'll try to explain in as much detail as possible.
1979 AMC 304. Newly machined and rebuilt. Completed engine break-in without issue and changed oil and filter. Started engine after oil change and had no oil pressure. Had to pack oil pump with vaseline to prime pump again and regained oil pressure. Pressure was 50-60 when cold and about 20-25 at warm idle at about 800 RPMS.
Still had some work to do before jeep was road ready but I would run it from time to time in yard. After running it one of those times and shutting it down my son asked to take another ride and when i started it, again no oil pressure. I again had to repack pump to regain prime. After this happened the second time I began trying to troubleshoot what could be causing pump to lose prime and all I could come up with was that I had installed an oil filter re-location kit and mounted oil filter on frame which is below the oil pump so I thought maybe oil was able to drain out of pump into oil filter and lose prime. I moved oil filter to fender above the pump and primed again. Ran engine in yard for 15-20 mins. Started engine again about 2hrs later and again no oil pressure.
Since then I have reinstalled the original oil filter adapter and am now back to the oil filter relocation kit setup attempting to regain oil pressure using a drill and a priming tool.
At this point I have the oil filter relocation kit in place and have verified that the oil pump is in fact pumping and I have oil going through block and getting to gauge but no oil coming up through push rods. Pressure reading on gauge is about 5-7 lbs. I am using a 1/2 industrial drill at 850 RPM's.
That is probably clear as mud. Any help would be appreciated.


'81 Scrambler AMC 304 Rear Dana 44 Front Dana 30
In pieces in middle of body off restore
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post #2 of 18 Old 05-01-2013, 02:26 PM
Matt1981CJ7
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Have you checked the relief valve? It should slide freely in the housing. I had to clean mine with a wire shotgun cleaning brush.

Did you plasti-gauge the tolerances between the pump gears and the pressure plate?

Matt
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OilPump3.jpg   OilPump2.jpg   OilPump1.jpg   OilPump4.jpg  
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post #3 of 18 Old 05-01-2013, 03:09 PM
82JeepCJ7
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What oil filter are you using? There should be a anti-drain back feature in it.

Also, when the oil pick up was installed, did it have the plastic knob on the bottom to prevent it from sticking to the bottom of the pan?


Beat it to fit, paint it to match!

Wheel, Wrench, Repeat.
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post #4 of 18 Old 05-01-2013, 03:24 PM
Matt1981CJ7
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82,

I don't think the factory pickup has the plastic spacer. Mine didn't.

But, you are correct, the bottom of the pickup should be approx. 3/8" off the bottom of the pan. A balled up piece of foil works nicely to check it during assembly.

Matt
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post #5 of 18 Old 05-01-2013, 03:59 PM Thread Starter
st3dnut
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I did check the clearance with plastic gauge initially. But when I pulled the pump apart this last time I did notice markings on the pressure plate as though the gears were touching it. I have ordered 3 different size gaskets and will redo clearance check this wknd when I get off.

The relief valve plunger was moving freely.

The plastic tab was on the pick-up tube when I put it together but ill drop the pan to verify its still in place.

Would lack of the correct clearance be enough to stop pump from getting oil up through the push rods?

'81 Scrambler AMC 304 Rear Dana 44 Front Dana 30
In pieces in middle of body off restore
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post #6 of 18 Old 05-01-2013, 04:16 PM
Matt1981CJ7
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Hmmm....I think it's normal to show minor markings on the pressure plate. The gears are free to move inside the housing. I think lack of proper tolerances would display consistently low pressure, not zero pressure like you are seeing.

A decent drill with priming tool should create 20 lbs + in just a few seconds of spinning.

You didn't double up on a filter gasket, did you?

Matt
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post #7 of 18 Old 05-01-2013, 04:41 PM
Dadamsnv
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Might be a long shot, but if your oil pressure gauge is electric, it may be faulty. Try a mechanical one if it is electrical.

Cheers!
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post #8 of 18 Old 05-02-2013, 08:58 AM Thread Starter
st3dnut
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It's been a mechanical gauge from the start.

I don't think I doubled up on the gasket but I will double check that to.

Although I'm not sure how or why it would happen, I guess my biggest concern was/is that it may be a bearing issue.

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post #9 of 18 Old 05-02-2013, 09:16 AM
Matt1981CJ7
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For some reason I keep coming back to the relief valve sticking in the open position.

That's the only "easy" thing I can think of that would cause a sudden, and sporadic, loss of pressure, and would prevent the system from pressurizing with a priming tool.

Anyone else?

Matt
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post #10 of 18 Old 05-02-2013, 11:33 AM
Dadamsnv
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Quote:
Originally Posted by Matt1981CJ7
For some reason I keep coming back to the relief valve sticking in the open position.

That's the only "easy" thing I can think of that would cause a sudden, and sporadic, loss of pressure, and would prevent the system from pressurizing with a priming tool.

Anyone else?

Matt
If the relief valve was stuck wide open, I would think it can easily cause these issues.

Did you do any oiling mods?

Also, at 5psi and 850 RPM with cold oil, I'm not surprised your pushrods aren't oiling.

I know you tried several different filter configurations/locations, but have you tried the stock position?

Cheers!
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post #11 of 18 Old 05-02-2013, 12:08 PM Thread Starter
st3dnut
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Quote:
Originally Posted by Dadamsnv

If the relief valve was stuck wide open, I would think it can easily cause these issues.

Did you do any oiling mods?

Also, at 5psi and 850 RPM with cold oil, I'm not surprised your pushrods aren't oiling.

I know you tried several different filter configurations/locations, but have you tried the stock position?
No other oiling mods other than the filter relocation kit from Bulltear.

The 5psi is what I have right now using a priming tool and a drill. When the engine was running before I lost pressure I would have 50-60 psi when cold and 20-25 when warm at 800 RPM IDLE.

By stock position, I'm assuming you mean the stock oil filter adapter?

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post #12 of 18 Old 05-02-2013, 12:12 PM
Dadamsnv
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Quote:
Originally Posted by st3dnut

No other oiling mods other than the filter relocation kit from Bulltear.

The 5psi is what I have right now using a priming tool and a drill. When the engine was running before I lost pressure I would have 50-60 psi when cold and 20-25 when warm at 800 RPM IDLE.

By stock position, I'm assuming you mean the stock oil filter adapter?
Maybe? "Adapter" throws me off.

Cheers!
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post #13 of 18 Old 05-02-2013, 01:31 PM
82JeepCJ7
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Just to eliminate it as a possibility, put a new filter on where the oil relocation kit is and remove that from the system.

Beat it to fit, paint it to match!

Wheel, Wrench, Repeat.
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post #14 of 18 Old 05-02-2013, 04:15 PM
Dadamsnv
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Quote:
Originally Posted by 82JeepCJ7
Just to eliminate it as a possibility, put a new filter on where the oil relocation kit is and remove that from the system.
^^^this.

Thanks, I have a hard time using my words

Cheers!
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post #15 of 18 Old 05-05-2013, 11:46 AM Thread Starter
st3dnut
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Update..
Replace oil filter
Checked oil pump gear clearance. Clearance was over .006. Was able to find a thinner gasket. Not sure of the size but it's definitely thinner than what was in there. Checked clearance with new gasket. Clearance is now btwn .003-.004. Preferred is .002.
Removed relief plunger and cleaned until plunger would literally fall in and out of channel.

Ran pump with drill and priming tool and basically the same pressure(6psi) but I do have oil coming through push rods to top of engine.

Reassembled everything and started engine.

Needle is barely above zero at idle of bout 800 RPMS. Reeve engine to bout 2000 RPMS and get to bout 20psi.

'81 Scrambler AMC 304 Rear Dana 44 Front Dana 30
In pieces in middle of body off restore
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