I am a heavy diesel truck mechanic. Found out by trial and error that you can stop the various injection pump leaks caused by ultra low sulfur fuel by adding "1 gallon of ethanol gasoline" from a "ethanol" pump to a full tank of diesel fuel (9-10 gallons). May need to use only a 1/2 gallon too. In a couple of days, the leaks stop. Apparently the ethanol swells the rubber seals and o rings back to original shape. Usually only one treatment is needed, although a 2nd one is possible. I have been driving my 2 rabbits for over 2 years with no ill effects from this fix. Both were leaking fuel in small amounts due to the dreaded "ULTRA LOW SULFUR FUEL". I do not know if it would work for the newer electronic engines or not. I would be afraid to try it on the newer injectors, but it works GREAT for old school diesels.
PS: I am talking about the alternative ethanol fuel pumps that can be found at various gas stations across the USA. Not the gasoline that has about 10% ethanol added, but the alternative fuel kind.