Fuel in the injection pump FL 120

[Fotoman]

Doing regular maintenance on my FL 120, I discovered fuel in the injection pump oil. This is the first time it happens as I have been changing the oil in the pump once or twice a season for the last 10 years. I vaguely remember reading something about this issue on the forum a while back but I was not able to find the thread.

The first couple of questions that come to mind are: what is causing fuel to end up there and is this a serious issue?

Thanks