D330, D333, 3304, 3306 – Fuel System

1. Fuel return to fuel tank or standpipe (if so equipped). 2. Fuel filter bypass valve. 3. Fuel filter. 4. Fuel injection pump. 5. Precombustion chamber. 6. Fuel supply line. 7. Primary fuel filter. 8. Fuel transfer pump. 9. Fuel transfer pump bypass valve. 10. Fuel injection pump housing fuel manifold.

The fuel system is a pressure type with a separate injection pump and injection valve for each cylinder. Fuel is injected into a precombustion chamber, not directly into the cylinder.

A transfer pump supplies fuel to the manifold from which the injection pumps get fuel. Before the fuel is delivered to the manifold, it may be filtered first by a primary filter attachment which removes dirt particles, and is filtered by a final filter which removes more minute particles.

The transfer pump can supply more fuel than is required for injection, so a bypass valve is used to limit the maximum pressure within the supply system.

The injection pumps receive fuel from the manifold and force it under high pressure to the injection valves. The injection valves spray atomized fuel into the precombustion chambers.

An air vent valve in the system permits removal of air. Air is removed by opening the valve and pressurizing the fuel system. The system can be pressurized by using the priming pump. The vent valve must be open until a stream of fuel, without air bubbles, flows from the vent line.

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