For the costs involved, I'd call Phil (Buy Parts link at the top of the page) and order a yard/meter of Diesel injector return line. Cut new lines to the lengths of the old lines and clean the injector wells with something like brake parts cleaner. See if that helps with the smell. If not, dig into it further.

On beside and under the injectiop pump is a series of fuel hoses. Fuel comes through a hard line from the fuel tank to a rubber hose to a plastic fuel filter to another hose to a fuel thermostat. The fuel thermostat has a hose to the lift pump attached to the injection pump as well as outbound and return lines to the fuel heater in the cylinder head. Lots of rubber hoses that degrade over time. Check for fuel leaks or dampness in that entire circuit or just replace all the rubber hose segments. Good time to upgrade to Viton hoses if you plan to run biodiesel.

There are lots of other fuel leak sources to check in and around the injection pump. I'd make sure it's not anything else before buying new injectors you might not need.

Sixto
87 300D