Fuel Tank Unit: Description and Operation

The Fuel Delivery Module (FDM) Includes:

- A high pressure fuel pump
- Venturi jet pump
- supply check valve
- A shuttle selector valve

High Pressure Fuel Pump
- The in-tank, high pressure pump replaces the need for a two pump fuel delivery system that requires a low pressure pump in the tank combined with a frame mounted high pressure pump. The high pressure fuel pump is cable of supplying 105 liters (27.7 gallons) per hour at a working pressure of 270 kPa (123 psi). The pump has an internal pressure relief valve to provide overpressure protection in the event fuel flow becomes restricted. Overpressure is restricted to 850 kPa (123 psi) and reduced fuel flow will result.

Venturi Jet Pump
- A portion of the high pressure flow from the pump is diverted to operate the venturi jet pump. The venturi pump draws fuel from the tank into the FDM reservoir to augment the engine return flow. This process ensures an adequate fuel supply to the pump during extreme vehicle maneuvers and steep vehicle altitudes with low-tank fill levels.

- The inlet of the venturi pump has a nylon filter on it to prevent dirt and other particulate matter from entering the system. Any water accumulation in the fuel tank can pass through the filter without restriction.

Supply Check Valve
- The supply check valve, normally closed, opens when the outlet pressure from the energized pump exceeds opposing check valve spring force. When the pump is de-energized (i.e., engine is shut-off), the supply check valve closes to maintain pump prime and fuel supply line pressure.

Shuttle Selector Valve (Dual Tanks)
- The shuttle selector valve opens the return line to the tank when the fuel pressure on the shuttle diaphragm exceeds the opposing spring force. The return flow is directed to the appropriate tank on vehicles equipped with dual tanks.