Fuel delivery system - V8 (Description): Description and operation (page 2 of 2)

NAS markets: A fabricated filler tube, made from stainless steel, connects the filler to the tank via a flexible rubber hose. The filler tube is connected at it's top end behind the filler flap.

On all vehicles that use unleaded fuel, the filler neck is fitted with an inhibitor. The inhibitor is a tapered nozzle in the mouth of the filler neck which will only allow the use of a standard unleaded fuel filler gun. A spring loaded flap valve prevents the incorrect fuel from being trickle filled from an incorrect filler gun.

Fuel tank breather system (all markets except NAS) The filler tube incorporates a tank vent which allows air and fuel vapour displaced from the tank when filling to vent to atmosphere via the filler neck. A relief valve in the vent line to the EVAP canister prevents vapour escaping through the canister during filling. This prevents the customer overfilling the tank and maintains the correct fuel cut-off level.

The filler tube also incorporates an integral Liquid Vapour Separator (LVS). During normal driving excess fuel vapour is passed via the vent line into the EVAP canister. To prevent the canister from being overloaded with fuel vapour, especially in hot climates, the vapour is given the opportunity to condense in the LVS. Fuel which condenses in the LVS flows back into the tank through the ROV's.

A breather spout within the tank controls the tank 'full' height. When fuel covers the spout it prevents fuel vapour and air from escaping from the tank. This causes the fuel to 'back-up' in the filler tube and shuts off the filler gun. The position of the spout ensures that when the filler gun shuts off, a vapour space of approximately 10% of the tanks total capacity remains. This vapour space ensures that Roll Over Valves (ROV's) are always above the fuel level and the vapour can escape and allow the tank to breathe.

The pressure relief valve fitted in the vent line to the EVAP canister prevents the customer trickle filling the tank. Trickle filling greatly reduces the vapour space in the tank which in turn affects the tank's ability to breathe properly, reducing engine performance and safety. When filling the tank, the pressures created are too low to open the pressure relief valve, preventing the customer from trickle filling the tank. Vapour pressures created during driving are higher and will open the valve allowing vapour to vent to the EVAP canister.

Four ROV's are welded onto the top surface of the tank. Each ROV is connected by a tube to the main vent line to the EVAP canister. The ROV's allow fuel vapour to pass through them during normal vehicle operation. In the event of the vehicle being overturned the valves shut-off, sealing the tank and preventing fuel from spilling from the vent line.

Fuel tank breather system (NAS) The filler tube incorporates a tank vent which allows air and fuel vapour displaced from the tank when filling to vent to atmosphere via the filler neck. A filler cap operated valve within the fuel filler neck prevents vapour escaping through the EVAP canister during filling. This prevents the customer overfilling the tank and maintains the correct fuel cut-off level.

The filler tube also has an 'L' shaped, stainless steel Liquid Vapour Separator (LVS). During normal driving excess fuel vapour is passed via the vent line into the EVAP canister. To prevent the canister from being overloaded with fuel vapour, especially in hot climates, the vapour is given the opportunity to condense in the LVS. Fuel which condenses in the LVS flows back into the tank via the LVS vent line and through the Roll Over Valves (ROV's).

For NAS vehicles with vacuum type EVAP system leak detection capability, a small tube is located alongside the filler tube and terminates near to the filler neck. The tube is connected to the On Board Diagnostics (OBD) pressure sensor in the fuel pump and provides the sensor with a reading of atmospheric pressure to compare against the tank pressure. EMISSION CONTROL - V8, DESCRIPTION AND OPERATION, Emission Control Systems.

A breather spout within the tank controls the tank 'full' height. When fuel covers the spout it prevents fuel vapour and air from escaping from the tank. This causes the fuel to 'back-up' in the filler tube and shuts off the filler gun. The position of the spout ensures that when the filler gun shuts off, a vapour space of approximately 10% of the tanks total capacity remains. This vapour space ensures that the ROV's are always above the fuel level and the vapour can escape to the LVS and allow the tank to breathe.