Thanks, HS - I'll have a closer look at it when I'm down there next and try your suggestion. I'm not sure where to get Volvo parts around here, but these engines are pretty common (old Perkins) so I should be able to find someone close by!
Originally Posted by sawingknots
i'm not familiar with that engine,but is the leak coming from under the pump retainer or from the bolt hole its-self,if so and just tightening it doesn't stop the leak you could try a copper washer
The leak is coming from under the plate. There is a shim under there that controls the injector timing - hence my reluctance to just hoe in with a spanner - and the leak appears to be around the shim.
I suspect I'll find it's the gasket that's gone and the bolt isn't loose at all and if that's the case, overtightening to stop the leak will just stuff things up further.
I'll play around with it over the weekend, but if I get into trouble I've got a mechanic coming out early next week (it's about time for a service anyways) and will post the outcome.