Fuel oil leaking around pump

After testing my TL120 which I just finished rebuilding, I noticed a lot of fuel around the base of the lamp. Upon further investigation I noted the fuel was coming from the pump stem. When I removed the pump, the pump assembly was full of fuel. Anyone have any ideas. Thanks in advance.
Clyde

 

The most likely cause is that seal in the non return valve needs to be replaced.

 

Thanks Jeff. I presume you mean the one located in the bottom of the pump.

 

Yes, that is correct.