Description And Operation
The system consists of the following main components:
- (1) Filler pipe
- (2) Tank complete with fuel pump and level sensors
- (3) Fuel supply pipe from the fuel pump to the high pressure system
- (4) High pressure pump (left bank)
- (5) High pressure pump (right bank)
- (6) High pressure fuel rail (left bank)
- (7) High pressure fuel rail (right bank)
The fuel filler pipe is closed at the end with a cap (3) that has no key-closure device. The "overflow" fuel breather and vapor recovery pipe (2) is positioned a few centimeters lower from where fuel is introduced. This pipe is connected to the fuel vapor line to the active vapor canister pipe (2) that carries the fuel vapors to the inlet of the active charcoal filter box.
The fuel cap allows air to enter the tank but at the same time prevents fuel vapors from exiting. When the fuel level in the tank goes down, a vacuum is created in the fuel filler pipe that overcomes the spring pressure, opening the valve (1) allowing air to enter through small slits in the cap's sides
On the end of the fuel filler pipe (1) inside of the fuel tank (3) there is an Inlet Check Valve (ICV) (2) that allows the fuel to enter the fuel tank but prevents the fuel and vapors in the tank from returning up the fuel filler pipe.
The tank has the classic "saddle" shape in order to create the space needed for the drive shaft and the exhaust pipes.
The tank is divided into two chambers: the main chamber (A) and the transfer chamber (B). The transfer chamber is larger than the main chamber.
Components located in the fuel tank used to supply fuel to the high pressure system and fuel vapors to the active charcoal canister are:
- (1) Fuel pump
- (2) Vent valve
- (3) Fuel vapor accumulator
- (4) Anti-shock support
The fuel pump module is placed in the main chamber (A) and is controlled by the Fuel Pump Control Module (FPCM) which is located outside of the fuel tank. Refer to MODULE, FUEL PUMP CONTROL, DESCRIPTION AND OPERATION .
Components of the fuel pump module are:
- (1) Pipe connection to send fuel vapors to the active charcoal canister
- (2) Pipe connection to send fuel to the high pressure fuel pump
- (3) Main chamber A float
- (4) Main chamber A level sensor
There are two level sensors inside the fuel tank. The sensor that measures the main chamber A level and one that measures the level in the transfer chamber B.
Components of fuel level sensing are:
- (3) Main chamber A float
- (5) Transfer chamber B float
- (6) Level sensor for transfer chamber B
As well as the double level sensor, the fuel pump module has two fuel pick-ups. The need for two pick-ups is due to the tank shape. The fuel tank is divided into two chambers due to the location of the drive shaft (1) and exhaust pipes (2). In the main chamber, the pump (P) sucks the fuel from a basket in the lower part of the fuel pump module and the main chamber side pick-up (4). In the transfer chamber, the fuel is sucked up by the transfer chamber pick-up (3).
The purpose of the three pick-ups is to ensure the pump basket is always full of fuel. The three pick-ups use the venturi effect to draw fuel into the basket.
The side pick-up in the main chamber is connected to a venturi which receives a constant flow of fuel from one of the pump supply lines. The fuel flow sent from the pump, passing through the venturi converging/diverging channel, creates a vacuum, fuel coming from the supply pump mixes with the subsequent fuel and flows back to the upper section to fill the basket. This same method (venturi effect) is used to draw fuel through the transfer chamber pick-up.
To draw fuel through the basket pick-up, the flow of fuel (A) from the fuel pump is sent through a venturi placed in-line with the pick-up. The fuel flow passing through the venturi creates the necessary vacuum to suction the fuel from the tank. The suctioned fuel contributes to maintaining the fuel level in the basket.
The fuel flow sent from the pump to the venturi, (A) in part flows back upwards (B) to supply the venturi that allows suction from the transfer chamber float connection (1).
The connection shown in illustration (1) receives the fuel flow from the transfer chambers pick-up. The connection is linked to a venturi which is powered by fuel flow (B). This allows the transfer chamber pick up to transfer fuel.
From the in-tank fuel pump module, fuel is sent through the high pressure fuel pumps (6-7) to the two high pressure fuel rails (10-11) via the fuel supply lines (1) and the high pressure supply lines (8-9).
- (1) Fuel supply lines
- (2) Pressure and temperature sensor
- (3) Metal connection pipe
- (4) Metal connection pipe
- (5) T-fitting
- (6) Right bank high pressure pump
- (7) Left bank high pressure pump
- (8) Supply pipe from the left high pressure pump to the left rail
- (9) Supply pipe from the right high pressure pump to the right rail
- (10) Left bank fuel rail
- (11) Right bank fuel rail
The high pressure fuel pump features:
- (1) Flow rate regulator
- (2) Fuel supply to fuel rail
- (3) Fuel intake
- (4) Roller tappet
Right side shown in illustration, left side similar.
The high pressure pumps is directly operated by the intake cams. There are roller tappets between the cam lobes and the pump plunger stems to reduce friction.
There is also a fuel vapor separation system inside the fuel tank that uses the vent valves (1) to prevent fuel flow to the vapor separator (2) and only allow the vapors to pass. The fuel vapors converge inside the separator (2) where they are sent to the active charcoal canister.
The fuel vapor separator receives vapor from the side vent valves (A) and central vent valve (B). A venturi pipe (C) sucks any remaining fuel from the separator and only fuel vapor is sent to the active charcoal filter.
The vent valves are placed in the upper part of the fuel tank. When refueling, the fuel level rises until it enters the holes in the bottom of the valve (A). The float (B) goes up at the same time as the fuel level until it closes the passage hole (C). This way, fuel is prevented from entering fuel vapor separator. When the fuel level is below the vent valve, float (B) opens up the passage hole (C). When the vapor pressure rises inside the tank, the ball above the passage hole (C) lifts up, allowing the vapors to pass (D).