Help Please got a leak :(

[CJ_Derv]

Thanks for replies guys,

It is the big timing bung as Darren mentioned just whipped it to the diesel specialist few streets up from work this morning. hes given me a o ring and new copper seals for delivery valve free and the special tool for the big triangle nut for a few days. he said the same as you darren hes only ever seen one or two leak in his 15 years working on pumps. But hopefully will have this fixed tonight and get my mpg back then time for more tuning

Thanks again

CJ