you my friend have a bad O ring!
Easy to replace - getting the O ring is not $$ either - the shipping kinda sucks on a .99 cent part! However, if you can get the specific size, you could go down to NAPA or anyone like that and get one. Get 1/2 dozen while you are there too!
I bought an entire O ring set at Northern Tool (Harbor Freight has them too) like 10 bucks.
Now, I'll tell you this, getting that mofo off can be fun! If you are dealing with the middle one, it is a grade A beeeaaauuuch! Unless of COURSE you take the first one out and then get to the middle one. ( I chose the hard way!
)
Here is what I did - I took a crappy ol 19mm wrench, cut a slot in it and allowed it to slide down the top.....after a lot of torque I snapped that 19 like a candy cane! Sooo..... I ground down the open end and allowed it to sit on the nut as I held the nut below with another wrench and then gave the 19 a couple of taps. YOU must take the line off first! THEN get the nut on top of the pump. DO not try to loosen the bottom nut only.
After taking the line off completely - you can get another box end down on top - I had to grind the side walls off the open end wrench to do it.
Once the nut is free - be careful to twist it off slowly, expect a little tension under it, and then once free - slide it up and pull out. The O ring will be there....and flat at day old beer too.
There are other parts that could come out, a spring and/or small ball ....so I have been told!
Pull the old O ring off, replace it, a little lube and retorque everything (except the top line where it goes into the injector.....)
If your machine has a decomp lever (it should at that age) - use it as you spin the engine over with the the throttle wide open, it will spit after a while and then will pump diesel down your injector. Tighten top nut and she should fire up and no leaks!
What I left out - someone will correct!