System Operation: Notes

OPERATION 

The fuel pump is a variable-speed rotary-vane type, which operates in a fuel pump module located in the right side of the fuel tank. A venturi transfer pump is located in the right side of the tank. The fuel pump module is secured in the fuel tank with a bayonet style locking ring that is welded into the tank structure. The fuel pump module has an integral top plate for the external pipe work and electrical connectors.

Fuel level is biased towards the right compartment in the fuel tank by drawing fuel through the internal cross over pipe via the jet pump, which serves to deliver a constant supply of fuel to the transfer pump and swirl pot assembly. High Pressure (HP) fuel from the fuel pump is directed through the jet pump's orifice, creating a Low Pressure (LP) area to be formed in the cross over pipe. The fuel is drawn into this LP area in the cross over pipe and directed into the swirl pot delivery pipes.

Fuel is pumped from the fuel pump to the engine mounted HP fuel pumps via the integral filter and Pressure Relief Valve (PRV).

The PRV assists engine starting by retaining a pre-set fuel pressure in the supply pipe and HP fuel pumps and the fuel rail. The PRV also limits fuel rail pressure due to temporary vapor increase in hot conditions and pressure caused by sudden load changes, for example, a fully open to closed throttle transition.

To meet ORVR (On-board Refueling Vapor Recovery) requirements, the fuel tank and associated components are designed to minimize fuel vapor loss during refueling. This is achieved by preventing fuel vapor from the fuel tank venting directly to the atmosphere. Instead, fuel vapor is directed into the evaporative emissions canister where it is stored before being purged at intervals to the engine's intake manifold.

North American Specification (NAS) vehicles feature additional connections and pipes at the rear of the filler head and also incorporates a Diagnostic Module Tank Leakage (DMTL) pump for leak detection requirements.