Looks like you've got a leaky shaft seal. Biodiesel decomposes rubber fuel lines and the rubber seals that are likely in your injection pump (unless it was resealed within the last 8 years or so, in which case they are B100 compatible). Switching between diesel and B100 often aggravates decomposition. Hoses will start to get tacky and wet at the ends when they're on their way out. The two most likely seals that are leaking on your IP are:

-the high pressure pump head, which is what the throttle lever and return line are on (4 flathead screws hold it on). This seal can be replaced w/o removing IP but there is a very real risk of damaging the IP if you don't know what you're doing.

and...
-the shaft seal, located at the rear end of the IP behind the sprocket. This can only be replaced with the IP out. Replacing it isn't hard but removing the IP is a good bit of work. Some may say that you will need the special tools, but I have gotten away multiple times without them by either making them or just spot marking. I just got done resealing my IP and going through this whole procedure myself. I could walk you through it if you want to tackle it, but know you'd be looking a the better part of a day's work.

As for the wiring harness: don't bother buying a new one. Consider yourself lucky that it's a diesel with 6 wires and not a gasser with about 20. You can rebuild it very easily using 14ga. (yellow) butt splices and some 16ga wire.

Charlie
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1980 244 diesel M46 169k, my 4th 240
1985 244 DL B230 M46 170k, my 5th