Farmall MD injection pump update (pic)

SW EM

Member
Hey everyone!

I had some time to work on it today. I got the plunger apart and cleaned up. That was quite a battle disassembling it!

I also took apart the distributor block to free up two stuck valves. I made a special tool to take the hex plugs out. I drilled a 11/64 hole in a 7mm allen socket. I am able to push in on those spring loaded valves now and they return.

Here is where I need some more advice from you guys who have lots of experience with these pumps. I can see the tops of the tappets that ride on the camshaft. As the engine turns over those tappets rise very slightly (.020) like they are supposed to, but then I have to tap them back down using a brass punch. I cannot push them down, they have to be tapped. I worry that the distributor block won't have enough spring force to push them back down either...

Is this normal? Would the fuel pressure inside the distributor block increase the down force on the tappets? Or should I tear into the pump further and remove those tappets and clean their bores. Thanks everyone!
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i would keep going and be sure things are free and lubed . if there is some parts rusted up there is quit surely more as u go. any rust in bores is just another wear agent.
 
Yes the tappets on top of the cam must come back down on their own. If you have to tap them with a drift they are not loose enough.

When I resealed a pump last winter I did the same to make a tool to pull the distributer block apart. I had mine completely part to reseal it.
 
SWEM, In your second picture the geared bar in the large hole is your rack linkage. Where that meets the pump is where the rack get stuck, need to be free and move easy.
I found after taking the pump apart there is very small check valve on the piston in there that will clog very easy with old fuel slim. you need to take that pump apart clean piston and all the little check valves. This and the relief valve on the return side are very important for the pump to work correctly. oldiron29
 
oldiron29,

The rack is free and moves easily. I have cleaned the pressure return valve near the top of the plunger. And there is also a scavenging valve near the bottom of the pump.

I had been getting pressure at the gauge, but none at the injectors. Now I want to make sure that cam lifters are in working order before reassembling.
 

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