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Discussion Starter #1 (Edited)
I'm hoping there are some John Deere M aficionados in this forum.

To make a long story shorter, I'll start here. I had my engine rebuilt 2 years ago. After re-assenbly the engine did not have enough oil pressure to lubricate the valve train (i.e. the oil was never getting to the head).

I have tried everything I can think of to remedy this, including replacing the pump with another used pump. Neither of the pumps make pressure. I've also tried changing the number of washers in the pump by-pass vale, both increased and decreased the number of washers. No change. I gave up and the tractor has just sat for 2 years.

If these pumps are worn out of tolerance; to the best of my knowledge and research,one cannot buy a new one nor sufficient new parts to rebuild one. In particular a new pump housing. I have no way to test the pumps off the tractor, other than to say that putting the pumps into a pan of oil and spinning it by hand, it does push oil.

Can anyone think of an alternative cause for this issue, other than pump wear? Is it possible that the machine shop did something wrong during the reassembly to allow an internal leak that would be dumping the oil back to the pan not allowing pressure to build in oil galleries?
 

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Discussion Starter #3 (Edited)
A blockage was high on my list of considerations, yes. I'm able to blow air through the galleries from the oil flter bracket down to the point where the oil pump joins the galley and up into the head. That would be the rear half of the engine block and the passage to the head. The front gallery dumps out into the govenor housing, but I would have to unbolt the govenor housing to verify that gallery clear.

This afternoon I dis-assembled the extra oil pump and it looks to be in great shape (no signs of abnormal wear), so I'm no longer thinking it is a pump issue.

I'm really stumped on this one. Very strange. Starting to wonder if the block itself was damaged internally where the pump connects to the gallery. That might take removal and dis-assembly of the engine for inspection. Still thinking through that senareo. Errrrr
 

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Can you remove the distributor and with some form of an extension, spin the pump with a drill?
Also does it read oil pressure on the gauge (presuming it has one).
 

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Discussion Starter #5
Engine Block Issue Maybe

Can you remove the distributor and with some form of an extension, spin the pump with a drill?
Also does it read oil pressure on the gauge (presuming it has one).
We know the pump is spining, because the distributer spins when the engine fires and runs (I start for a few seconds and I then cut the ignition). The distributor is driven by a grear on the pump shaft end; as you likely already know. I've spun the oil pump off tractor in a pan of oil and it pushes oil. I'm now of the opinion the oil is leaking off into the pan somewhere near where the oil galleries begin. i'e. something broke in the block.

Iwill pull the pan and the pump again and use my bore scope to inspect up in that area. If it's broken there, the problem likely goes back to before I had the engine rebuilt and the machine shop didn't pick up on the failure.
 

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Ok. so with the help of another. Pull the distributor. Drop the pan and leave the oil pump in place. Put a large enough pan under the engine to collect the oil. Hook up a temporary connection to the pump. Have your friend / wife spin the pump with a drill. While it is spinning and (not spining the motor) pumping oil. Lay down under the tractor and look to see if oil appears to be pouring out of one location. If you have good oil pressure (I suspect you do) you will probably only see a rain forrest of oil seeping from the joints. Tho if you do have a broken spot (hopefully not the block) it will just pour out at the one spot.

At least that is how I would proceed to try and analyze the situation. Good luck
 

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Discussion Starter #7 (Edited)
Today I pulled the pump and inspected the pump internals. The gears fit nicely actually look like new. I can't imagine this pump not working.

Your suggestion is a reasonable one. I'll try to figure iout a way to do that. It will most certainly make a mess of oil on me and the garage floor :)

Thanks for the idea and for following my post!

Update:
Woops! There is no way to spin the oil pump from topside when the pump is installed in the engine without spinning the engine. The oil pump is turned by a grear on the end of the pump shaft. That gear engages a companion worm gear on the camshaft. So, the only way the pump spins is when the camshaft is spinning and that is powered by a gear drive off the crakshaft.
 

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LOL make a oil pan of lexan then?

Only other way I can think of is to plug the area where the pump attaches and with an electric pump. Force feed oil into the system using the port for the oil pressure gauge.

Another thought. Presuming the rebuild shop didnt use a hot tank to wash the engine prior to a rebuild? Is to heat the engine to 400F. The older oils used wax as a lubricant. For this sole reason is why I frown when some one here tells a person that straight motor oil is fine. The new detergent stuff has chemicals that help break down the wax buildup. Yet these posters whom say the old non detergent oil is better, really dont realize what they are saying. So you may need to cook the engine to get the wax out from an older oil use.

Good luck and update us when you can.
 
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