Question about 2240 injector pump leaking bolt

Im actually writing for my uncle. Hes elderly and has an issue that he can not figure out. I will try to explain as best I can. Please bear with me.
He has a 2240 John Deere. I have all the numbers off of the plate if that will help. On the injector pump it has what I call a nut or screw on the lower side I believe it may be an octagon type shape. Its very very short and has a gasket or seal around the inside top. Diesel began leaking from this bolt and he took it off. He needed a new seal, he got that and put it on. When he tightened it back, he must have tighten too hard and he crossthreaded I believe the pump part where the screw goes. I dont believe its bad. But its definitely broke. It is leaking fuel. Will he need a new injector pump or is there a way for this to be repaired? He was told by one place to use JB Weld. He doesnt want to have to buy a new one. Is that his only option or is there another remedy. Im hoping I explained this to be understood. I have zero knowledge of anything about a tractor. If I didnt explain thoroughly enough, I can try to find a picture.
Thank You in advance. I appreciate it.

Welcome to YT

Here's the parts diagram. Key 12 is an o-ring part number R27564

You definitely know your stuff. Im a female & know nothing about what Ive been asking. But I can tell you do. The bolt did have a spring on it.

What is your recommendation?
So its a Lucas/Delphi DPA style?

It's not common, but I've seen the advance block housings crack before too. Had a pump in for repair last summer with a cracked housing. No seals or gaskets will repair it if there's a crack involved. Had to replace the advance block on that one.

I believe the bolt Im talking about looks something like the one in pic. This is not his. Just a bolt similar to his.

That's the advance piston spring cap. Those seldom leak, but leaks higher up can make it appear to be leaking..

Here is all the info and Thank You for replying.
John Deer

Model no 2240

SN 309835

Injector information

Tag data
AR78634

3432640

072698 PV

Definitely a CAV DPA model pump. May also have RotoDiesel on the housing side..

List the complete pump model number, sounds like a CAV DPA with the bolt on advance. There's a good chance the leak was not there in the first place, as most leaks on that pump are higher up, and then drip off the bottom. Pump MAY need completely torn down to see what damage is done, hopefully the hydraulic head is still serviceable. I've repaired a lot of DPA pumps that owners swear it's leaking at the bottom..