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Home >> Pontiac >> 2009 >> Vibe FWD L4-1.8L >> Repair and Diagnosis >> Powertrain Management >> Computers and Control Systems >> Description and Operation >> Fuel System Description >> Part 2

Part 2





Fuel Pressure Regulator

The fuel pressure regulator is located in the fuel tank and is part of the fuel sender assembly. The fuel pressure regulator is a diaphragm-operated pressure relief valve consisting of a diaphragm, a spring, and a valve. The fuel pressure regulator is inserted into the fuel sender assembly and sealed with double O-ring. A correctly calibrated fuel pressure regulator ensures that the fuel is delivered to the fuel injectors at the correct pressure.

Quick Connect Fittings

Quick connect style fuel fittings provide a simplified means of installing and connecting the fuel system components. Depending on the vehicle model, there are 2 types of quick connect fittings. Different types of fittings are used at different locations in the fuel system. Each type of quick connect fitting consists of a unique female connector and a compatible male fuel pipe end. O-rings located inside of the female connector provide a leak proof seal. Integral locking tabs or fingers hold the quick connect fittings together. A special tool is used to service the quick connect fittings.

Fuel Feed Pipes and Hoses

Warning

In order to Reduce the Risk of Fire and Personal Injury:

* If nylon fuel pipes are nicked, scratched or damaged during installation, Do Not attempt to repair the sections of the nylon fuel pipes. Replace them.
* When installing new fuel pipes, Do Not hammer directly on the fuel harness body clips as it may damage the nylon pipes resulting in a possible 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.
* Before connecting fuel pipe fittings, always apply a few drops of clean engine oil to the male pipe ends. 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.)

The fuel feed and return pipes and hoses carry the fuel from the fuel tank to the fuel injectors. These pipes and hoses are attached to the underbody of the vehicle and should be inspected periodically for kinks or dents that could restrict the fuel flow.

Fuel Vapor Pipes and Hoses

The fuel vapor pipe and hoses carry the fuel vapors from the fuel tank to the evaporative emission (EVAP) canister located at the rear of the vehicle, ahead of the fuel tank. The fuel vapors are stored in the canister when the engine is not running. When the engine is running at the normal operating temperature and the accelerator pedal is depressed, the powertrain control module (PCM) will command the EVAP canister purge valve to open and allow the stored fuel vapors to be purged into the intake manifold where the vapors will be burned in the combustion process.

On-Board Refueling Vapor Recovery System (ORVR)





The on-board refueling vapor recovery (ORVR) system is an on-board vehicle system designed to recover fuel vapors during the vehicle refueling operation. Instead of allowing fuel vapors to escape to the atmosphere, the ORVR system transports the vapor to the evaporative emission (EVAP) canister for use by the engine. The flow of liquid fuel down the fuel filler neck provides a liquid seal that prevents fuel vapor from leaving the fuel system. The ORVR system architecture varies from platform to platform. Some of the items listed below are optional depending on the platform application. The following is a list of all the ORVR system components with a brief description of their operation:

* The EVAP canister (1)-The EVAP canister receives and stores refueling vapor from the fuel system. The EVAP canister releases the fuel vapor to the engine through the EVAP control system.
* The vapor lines (2)-The vapor lines transport fuel vapor from the fuel tank assembly to the EVAP canister.
* The vapor recirculation line (3), if equipped-The vapor recirculation line transports fuel vapor from the fuel tank to the top of the fuel filler pipe during refueling in order to reduce the fuel vapor at the canister. The vapor recirculation line can be located inside the fuel filler pipe or outside of the fuel filler pipe.
* The variable orifice valve (4), if equipped-The variable orifice valve regulates the amount of vapor allowed to enter the vapor recirculation line.
* The fuel filler pipe (5)-The fuel filler pipe carries fuel from the fuel dispensing nozzle to the fuel tank.
* The check valve (6)-The check valve limits fuel spitback from the fuel tank during the refueling operation by allowing fuel flow only into the fuel tank. The check valve is located at the bottom of the fuel filler pipe or in the fuel tank filler neck.
* The fuel sender assembly (7)-The fuel sender assembly pumps fuel to the engine from the fuel tank.
* The fill limiter vent valve (8)-The fill limiter vent valve is typically located in the fuel tank and acts as a shut-off valve. The fill limiter vent valve performs the following functions:

- Controls the fuel tank fill level by closing the primary vent of the fuel tank.
- Prevents liquid fuel from exiting the fuel tank through the vapor line and entering the EVAP canister.
- Provides fuel-spillage protection in the event of a vehicle rollover by closing the vapor path from the tank to the EVAP canister.

* The pressure/vacuum relief valve (9), if equipped-The pressure/vacuum relief valve provides venting of excessive fuel tank pressure or vacuum. The pressure/vacuum relief valve is located in the fuel filler neck on a plastic fuel tank and in the fill limiter vent valve on a steel fuel tank.

Fill Limiter Vent Valve (FLVV)




1 - FLVV
2 - Atmosphere Chamber
3 - EVAP Canister
4 - ORVR Vent Line Inlet Port
5 - Vapor Chamber
6 - Vent Control Valve

The fill limiter vent valve (FLVV) (1) is an integral part of the EVAP canister (3). The cross sectional view shows the path of fuel vapors passing through the valve directly into the EVAP canister. When the fuel filler cap is removed during refueling, the atmosphere chamber (2) fills with atmospheric pressure that has entered through the port from the fuel filler pipe. The pressure in the atmosphere chamber (2) opens the passage to the vapor chamber (5) by opening the vent control valve (6). Refueling causes the internal pressure in the fuel tank to increase, pushing fuel vapors into the ORVR port (4) and up through the vent control valve (6) into the EVAP canister (3). When the fuel tank is full, the tank vapor control valve (5) closes, sealing off the passage into the EVAP canister.

Accelerator Controls

An electronic throttle control (ETC) system or throttle actuator control (TAC) system is used to control the throttle valve opening. The accelerator pedal receives input from the driver and the accelerator pedal position (APP) sensors send this information to the PCM. The PCM commands the desired throttle valve opening to the TAC motor on the throttle body. For additional information on the operation of this system, refer to Throttle Actuator Control (TAC) System Description (Throttle Actuator Control (TAC) System Description).

Fuel Metering System

The function of the fuel metering system is deliver the correct amount of fuel to the engine under all operating conditions. Fuel is delivered to each cylinder by the fuel injectors. The fuel injectors are controlled sequentially by the powertrain control module (PCM). The PCM bases the control of the fuel injectors on several important engine parameters. These engine parameters include the following:

* Engine speed (RPM)
* Mass air flow (MAF)
* Engine coolant temperature (ECT)
* Intake air temperature (IAT)
* Throttle position (TP)
* Fuel control oxygen sensor input (HO2S 1)

Determining air density is critical to proper air/fuel management. Air density is primarily derived from the MAF sensor input. The MAF sensor measures the air volume and determines the air density. Larger volumes of air and denser air masses require additional fuel. The information from the MAF sensor is used by the PCM in order to modify the fuel injector pulse width.

Fuel Injector





The fuel injector (1) is an electromagnetic (solenoid) type injection nozzle which injects fuel into the intake port of the cylinder head according to the signals from the powertrain control module (PCM). There are 4 fuel injectors, one for each cylinder, located between the intake manifold and the fuel rail.

The PCM energizes the solenoid coil of the fuel injector (1), generating an electromagnet field that attracts the solenoid plunger (2). The needle valve, which is incorporated with the solenoid plunger (2), is opened by the movement of the solenoid plunger (2). The opening of the needle valve allows fuel that is under pressure to disperse through a 12-hole plate (3) into a cone shaped pattern. Because the stroke of the needle valve in the fuel injector is set constant, the amount of fuel injected at one time is determined by the pulse width injection time, the length of time the solenoid coil is energized.
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