HI Everyone!

On my OM617, I've been experiencing rough idle since I bought it. It was extensively worked on by the previous owner (new injectors, filters, primer, service delivery valves, injector pump). He suspects air infiltration, so I replaced some lines with clear tubing.

When I prime my fuel system with a few pushes, any air easily passes from the secondary fuel filter to return to be removed. However, an air pocket exists from the injector return to the secondary fuel filter. Even though the engine starts easily, the air pocket still exists. I can only get rid of the air pocket after I give the car a lot of gas and direct it to the secondary fuel filter, then it is gone.

My concern is the fuel flow going through the return lines to the secondary filter. In comparison with the rest of the system, very little flows from the injector return. Could this be normal or is there is restriction? How much return flow is considered normal? Does that flow have a way to be measured?

Theseus
Murfreesboro, TN
84 300sd "Helga"