Fuel System
FUEL SYSTEM OVERVIEWThe fuel tank stores the fuel supply. The electric fuel pump supplies fuel through an in-line fuel filter to the fuel injection system. The fuel pump provides fuel at a higher rate of flow than is needed by the fuel injection system. The fuel pressure regulator maintains the correct fuel pressure to the fuel injection system. A separate pipe returns unused fuel to the fuel tank.
FUEL TANK
The fuel tank stores the fuel supply. The fuel tank is molded from high density polyethylene. The fuel tank houses the fuel sender assembly (4) and the fuel filter (7). The fuel tank is held in place by metal straps that attach to the frame. The fuel tank is located on the left side of the vehicle.
FUEL FILL PIPE
The fuel fill pipe (9) has a built-in restrictor (8) and a deflector in order to prevent refueling with leaded fuel.
FUEL FILLER CAP
NOTE: If a fuel tank filler cap requires replacement, use only a fuel tank filler cap with the same features. Failure to use the correct fuel tank filler cap can result in a serious malfunction of the fuel and EVAP system.
Fuel Filler Cap:
The fuel fill pipe has a tethered quarter-turn type fuel filler cap. A torque-limiting device prevents the cap from being over tightened. To install the cap, turn the cap clockwise until you hear audible clicks. This indicates that the cap is correctly torqued and fully seated. A fuel filler cap that is not fully seated may cause a malfunction in the emission system.
FUEL SENDER ASSEMBLY
Fuel Sender Assembly:
The fuel sender assembly consists of the following major components:
^ The fuel pump (1)
^ The float (2)
^ The fuel level sensor (3)
FUEL LEVEL SENSOR
The fuel level sensor is a part of the fuel sender assembly. The position of the float arm indicates the fuel level. The fuel level sensor contains a variable resistor which changes resistance in correspondence with the amount of fuel in the fuel tank.
FUEL PUMP
Fuel Pump:
The fuel pump is mounted in the fuel sender assembly. The fuel pump is an electric high pressure pump. The fuel pump provides fuel at a higher rate of flow than is needed by the fuel injectors. Excess fuel from the fuel rail assembly returns to the fuel tank through the fuel return pipe. The fuel pump delivers a constant flow of fuel to the engine even during low fuel conditions. The powertrain control module (PCM) controls the electric fuel pump operation through a fuel pump relay. The fuel pump flex pipe acts to dampen the fuel pulses and noise generated by the fuel pump.
FUEL FILTER
The fuel filter is located on the left side of the vehicle, near the fuel tank. The paper filter element (2) traps particles in the fuel that may damage the fuel injection system. The filter housing (1) is made to withstand maximum fuel system pressure, exposure to fuel additives, and changes in temperature. Replace the fuel filter if the filter is restricted.
FUEL FEED AND RETURN PIPES
The fuel feed pipe carries fuel from the fuel tank to the fuel rail assembly. The fuel return pipe carries fuel from the fuel rail assembly back to the fuel tank. The fuel pipes consist of 2 sections:
^ The rear fuel pipe assemblies are located from the top of the fuel tank to the chassis fuel pipes. The rear fuel pipes are constructed of nylon.
^ The chassis fuel pipes are located under the vehicle and connect the rear fuel pipes to the fuel rail pipes. The chassis fuel pipes are constructed of nylon and steel.
NYLON FUEL PIPES
CAUTION: In order to reduce the risk of fire and personal injury observe the following items:
^ Replace all nylon fuel pipes that are nicked, scratched or damaged during installation, do not attempt to repair the nylon fuel pipes
^ Do not hammer directly on the fuel harness body clips when installing new fuel pipes. Damage to the nylon pipes may result in a fuel leak.
^ Always cover nylon vapor pipes with a wet towel before using a torch near them. Also, never expose the vehicle to temperatures higher than 115°C (239°F) for more than one hour, or more than 90°C (194°F) for any extended period.
^ Apply a few drops of clean engine oil to the male pipe ends before connecting fuel pipe fittings. This will ensure proper reconnection and prevent a possible fuel leak. (During normal operation, the O-rings located in the female connector will swell and may prevent proper reconnection if not lubricated.)
Nylon pipes are constructed to withstand maximum fuel system pressure, exposure to fuel additives, and changes in temperature. There are 3 sizes of nylon pipes used:
^ 9.53 mm (3/8 in) ID for the fuel feed
^ 7.94 mm (5/16 in) ID for the fuel return
^ 12.7 mm (1/2 in) ID for the vent
Heat resistant rubber hose or corrugated plastic conduit protect the pipes that are exposed to chafing, high temperature, or vibration.
Nylon fuel pipes are somewhat flexible and can be formed around gradual turns under the vehicle. However, if nylon fuel pipes are forced into sharp bends, the pipes kink and restrict the fuel flow. Also, once exposed to fuel, nylon pipes may become stiffer and are more likely to kink if bent too far. Take special care when working on a vehicle with nylon fuel pipes.
QUICK-CONNECT FITTINGS
Quick-connect fittings provide a simplified means of installing and connecting fuel system components. The fittings consist of a unique female connector and a compatible male pipe end. O-rings, located inside the female connector, provide the fuel seal. Integral locking tabs inside the female connector hold the fittings together.
FUEL PIPE O-RINGS
O-rings seal the connections in the fuel system. Fuel system O-ring seals are made of special material. Service the O-ring seals with the correct service part.
FUEL RAIL ASSEMBLY
Fuel Rail Assembly:
The fuel rail assembly attaches to the cylinder head. The fuel rail assembly performs the following functions:
^ Positions the fuel injectors in the cylinder head
^ Distributes fuel evenly to the fuel injectors
^ Integrates the fuel pressure regulator with the fuel metering system
FUEL INJECTORS
Fuel Injectors:
The fuel injector assembly is a solenoid device, controlled by the PCM, that meters pressurized fuel to a single engine cylinder. The PCM energizes the high-impedance (12.0 ohms) injector solenoid (2) to open a normally closed ball valve (3). This allows fuel to flow into the top of the injector, past the ball valve, and through a director plate at the injector outlet.
The director plate has machined holes that control the fuel flow, generating a spray of finely atomized fuel at the injector tip. Fuel from the injector tip is directed at the intake valve, causing the fuel to become further atomized and vaporized before entering the combustion chamber. This fine atomization improves fuel economy and emissions.
FUEL PRESSURE REGULATOR ASSEMBLY
Fuel Pressure Regulator Assembly:
The fuel pressure regulator is a diaphragm relief valve. The diaphragm has fuel pressure on one side and regulator spring pressure on the other side. The fuel pressure regulator maintains a constant pressure differential across the fuel injectors under all operating conditions.