Fuel flows from fuel tank (E) through fuel strainer (G) to fuel filter (C). Water is separated from the fuel as it passes through the fuel filter and then flows to the fuel injection pump (A).
Vented fuel cap (F) will open to permit air to escape if fuel tank becomes pressurized. Vented fuel cap will also open to permit air to enter tank if sufficient vacuum is created.
Any air in the system is bled out with return fuel through fuel return line (H) to the fuel tank. Manual bleeding of fuel system is usually necessary only after servicing components of fuel system.
More fuel is routed through the system than is required for injection. Excess fuel serves to cool and lubricate the injection pump and nozzles, and warm the fuel in the fuel tank.
For information regarding fuel flow through the fuel injection pump, injectors and fuel filter; see Component Technical Manual—PowerTech 4.5L Diesel Engine Mechanical Fuel System.