Volvo D11F Operator's Manual And Maintenance Instructions page 59

Maintenance and Service 55
Fuel Filters
A primary fuel filter can be located on the engine or remote mounted on the
frame rail. This filter consists of a filter cartridge, a water separation bowl and
may have a fuel heater built in.
The secondary fuel filter is located on the left hand side, below the engine
electronic control unit (EECU). The filter is a spin-on filter.
D11F and D13F Engine-Mounted Fuel Filters (D13F shown, D11F similar)
1. Secondary Fuel Filter 2. Primary Fuel Filter with Water
Separator