YangDong 380: heavy diesel leak from Injector pump.

That is the crankcase/governor sump vent/overflow port.

I would start by completely draining and refilling the pump with fresh engine oil and monitor the overflow port to see if it is still overflowing. When the lift pump (the black housing above and to the right of your arrow) it will leak fuel into the pump crankcase and overflow it. It also dilutes the oil and can cause premature wear.

Take a look at this document starting on page 40 for more information on this.

http://www.harnerfarm.net/Jinma/Files/jinma_manual.pdf

Feel free to download a copy of this manual for your own use.

Yes, when it fails.

On mine the lift pump was actuated by a push rod that runs on a cam  inside the injection pump. The only seal between the IP pump and the fuel in the lift pump was a small o-ring. O-rings work pretty good in a static situation but are not so good in a sliding application like this one. After replacing the o-ring several times I got tired of the whole mess and just replaced the lift pump with an electric one. It was easy enough to make a cover plate and gasket to seal the IP crankcase.

I also found out that the banjo bolt fittings in the fuel line have a nice barbed nipple on the inside. Just cut the compression sleeve off and pull it out. Then it can be installed on a new fuel hose with a regular worm screw clamp. Wired the electric pump to a “hot when on” location and it has worked fine for several years.

To monitor the situation I made a little collection bottle from a clear pop bottle and connected it to the nipple on the overflow vent. As hours have built on the engine it has slowly developed a leak in the IP internally and is still getting fuel in the oil. Since it only takes 4 ounces or so, it is pretty easy to just change the IP sump oil more often. I am coming up on 900 hours on a tractor that was new in 2007 and have to change oil in the IP about every 25 hours.

Eventually the IP will need to be rebuilt or replaced, an expense I am not looking forward to, so frequent oil changes are the order of the day for now… Maybe I should replace the drain plug with a valve just to make it easier.