Description of the fuel system (Chevrolet Captiva 1)

Fuel tank

The fuel tank is made of high-density polyethylene. The fuel tank is secured with 2 metal clamps that are attached to the bottom of the car body. The fuel tank has a recess that allows for a constant supply of fuel around the mesh filter when the fuel level is low and during abrupt maneuvers.

The fuel tank is also equipped with a fuel vapor vent valve with anti-tip protection. The vent valve has a 2-stage ventilation calibration, which increases the supply of vapors to the adsorber when the pressure in the tank rises above a set threshold as a result of an increase in operating temperature.

Fuel tank filler neck

To prevent topping up with leaded fuel, the fuel filler neck has a built-in restrictor and deflector. Only the thinner unleaded fuel nozzle fits into the restrictor opening, which must be inserted completely to bypass the deflector. When refuelling, the tank is vented through a vent tube located inside the fuel filler neck.

Fuel tank filler cap

Note: If replacement is necessary, use a fuel filler cap with the same specifications. Using an incorrect fuel filler cap may cause serious damage to the fuel system.

The fuel filler cap is equipped with a ratchet vent screw to prevent overtightening.

The venting action allows the pressure in the fuel tank to be released before the cap is removed. Instructions for use are printed on the filler cap. The cap has a vacuum relief valve.

Fuel module

The fuel module assembly is installed in a threaded hole in a plastic fuel tank with a seal and a locking ring. The tank, which contains an external inlet mesh filter, an electric fuel pump and a pump filter, contacts the bottom of the tank. This design allows:

• Maintain optimum fuel level in the built-in fuel tank at any fuel level in the tank and while driving.
• Improve the accuracy of fuel level measurement in the tank
• Improve coarse filtration and provide additional filtration at the pump inlet
• It is better to isolate the internal fuel pump for quiet operation

The fuel module design maintains an optimal fuel level in the tank (flask). Fuel entering the tank is sucked in by the following components:

• The first stage of the fuel pump through an external mesh filter and/or
• secondary umbrella valve or
• return fuel line if the fuel level is below the top of the tank

Fuel pump; Gasoline pump; Electric fuel pump

The electric fuel pump is a turbine pump located inside the fuel module. The operation of the electric fuel pump is controlled by the ECM via the fuel pump relay.

Fuel module mesh filters

Mesh filters are used for coarse filtration, performing the following functions:

• Filtering of impurities
• Separation of water from fuel
• Creates a capillary effect that helps suck fuel into the fuel pump

If fuel stops flowing through the mesh filter, there is too much sediment or water in the fuel tank. In this case, the fuel tank must be removed and cleaned, and the mesh filter replaced.

In-line fuel filter

This fuel filter is located on the fuel supply line, between the fuel pump and the fuel rail. The electric fuel pump delivers fuel through a straight-through fuel filter to the fuel injection system. The fuel pressure regulator maintains regulated fuel pressure supplied to the fuel injectors. Unused fuel returns from the fuel filter to the fuel tank through a separate return fuel line. The paper filter element (2) traps particles contained in the fuel that can damage the fuel injection system. The design of the filter housing (1) allows it to withstand maximum pressure in the fuel system, the effects of fuel additives and temperature changes. There is no service interval for replacing the fuel filter. The fuel filter is changed when clogged.

Fuel vapor recovery system lines and hoses

The EVAP line runs from the fuel tank vent valve to the EVAP canister and into the engine compartment. The EVAP line is made of nylon and is connected to the EVAP canister with a quick-disconnect fitting.

Fuel pressure regulator

The fuel pressure regulator is connected to the return fuel line of the fuel module. The fuel pressure regulator is a diaphragm pressure reducing valve. The injector activation time is adjusted programmatically, since the fuel pressure regulator is not tied to the manifold pressure. The injector activation pulse duration is adjusted depending on the signals from the mass air flow (MAF)/intake air temperature (IAT) sensors.

With the engine idling, the fuel pressure in the system at the pressure test connector should be 380-410 kPa (55-60 psi). With the system pressure set and the pump off, the pressure should stabilize and be maintained. If the pressure regulator maintains too low or too high fuel pressure, this will negatively affect the drivability of the vehicle.

fuel rail

The fuel rail consists of 3 parts:

• Pipes delivering fuel to all injectors
• Fuel pressure control holes
• Six independent fuel injectors

The fuel rail is installed on the intake manifold and distributes fuel to the cylinders through individual injectors.

Fuel injectors

The fuel injector is a solenoid valve device controlled by the ECM. When the ECM energizes the injector coil, a normally closed ball valve opens, allowing the fuel mixture to flow through a guide plate to the injector outlet. The guide plate has holes that control the fuel flow and form a double cone of finely atomized fuel at the injector outlet. The fuel flow from the injector outlet is directed to both intake valves. As a result, the fuel is further evaporated before entering the combustion chamber.



Fuel injector malfunctions can cause a variety of drivability issues. The following types of malfunctions are possible:

• The injectors do not open
• Injectors stuck in open position
• The injectors are leaking
• The injector windings have low resistance

Fuel pump relay

The ECM controls the fuel pump via the fuel pump relay. The ECM always turns on the fuel pump relay when it detects pulses from the crankshaft position sensor.

Fuel supply to the engine

Fuel is supplied to the engine through six separate fuel injectors, one for each cylinder, which are controlled by the ECM controller. The ECM controller controls the injectors by applying a short current pulse to the nozzle winding at every second engine speed. The duration of this short pulse is carefully calculated by the ECM controller in such a way as to ensure that the amount of fuel required for good engine performance and reduced exhaust toxicity is supplied. The time that the nozzle is open is called the pulse width and is measured in milliseconds (thousandths of a second). During engine operation, the ECM continuously monitors the signals coming from the sensors and recalculates the required pulse width for each injector. When calculating the pulse width, the flow rate through the injector, the mass of fuel passing through the injector per unit of time, the desired fuel-air ratio and the actual mass of air in each cylinder are taken into account; battery voltage correction, short-term and long-term fuel injection correction are also introduced. The calculated pulse is applied at the moment of closing of the cylinder intake valves to ensure maximum duration and efficiency of evaporation.



Fuel delivery during cranking is slightly different from fuel delivery during engine operation. A prime pulse may be provided at the start of engine rotation to assist in starting. Once the ECM determines where the engine is in the ignition sequence, the ECM begins pulsing the injectors. The pulse width during cranking is dependent on coolant temperature and engine load. The fuel system has a number of automatic adjustments to compensate for variations in fuel system component characteristics, driving conditions, fuel used, and vehicle aging. The basis of fuel management is the pulse width calculation process described above. The calculation takes into account battery voltage compensation, as well as short-term and long-term fuel trims. Battery voltage compensation is necessary because injector voltage affects injector flow. Short-term and long-term fuel trims are fine and coarse adjustments to the pulse width to provide the best engine performance and reduced emissions. These adjustments are calculated based on feedback signals from the oxygen sensors in the exhaust stream and are only applied when the fuel system is operating in closed loop mode.

In some situations, the fuel injection system turns off the injectors for a certain period of time. This is called fuel cutoff. Fuel cutoff is used to improve traction, save fuel, reduce exhaust toxicity, and protect the vehicle in certain extreme or adverse situations.

If a major internal fault occurs, the ECM may switch to a backup fuel strategy (low power mode), which will ensure the engine operates until maintenance is performed.

Sequential Fuel Injection (SFI)

The ECM controls the fuel injectors based on information it receives from various sensors. Each injector is individually controlled in the order in which the engine fires. This is called sequential fuel injection. This approach allows for precise dosing of fuel to each cylinder and improves engine performance under all operating conditions.

The ECM has several fuel supply control modes depending on the information received from the sensors.

Start mode

When the ECM controller detects reference pulses from the CKP sensor, it turns on the fuel pump. A running fuel pump creates pressure in the fuel system. The ECM controller then determines the required pulse width for starting based on the signals of the mass air flow sensors, intake air temperature, engine coolant temperature and throttle position.

Free flow mode

If the engine floods with fuel during startup and does not start, you can manually select the flood elimination mode. To enter the flood elimination mode, you must press the accelerator pedal to the fully open position. In this case, the ECM completely disables the injectors and maintains this state as long as the ECM sees the accelerator in the fully open position at engine speeds below 1000 rpm.

Driving mode

The driving mode has two options: operation in open loop mode and closed loop mode. When the engine is first started and the speed is above 480 rpm, the system switches to "open loop" mode. In open loop mode, the ECM ignores signals from the oxygen sensors and calculates the required injector pulse duration based primarily on input signals from the mass air flow sensor, intake air temperature sensor, and engine coolant temperature sensor.

In closed loop mode, the ECM adjusts the calculated injector pulse length for each injector bank based on signals from the corresponding oxygen sensors.

Acceleration mode

The ECM monitors changes in the throttle position and mass air flow sensor signals to determine when the vehicle is accelerating. When this occurs, the ECM increases the injector pulse width to increase fuel delivery and improve engine performance.

Braking mode

The ECM monitors changes in the throttle position and mass air flow sensor signals to determine when the vehicle is in deceleration mode. In this case, the ECM reduces the pulse width or even temporarily turns off the injectors completely to reduce fuel delivery and improve deceleration (engine braking).

Battery voltage correction mode

If the ECM detects a decrease in battery voltage, it can compensate for the decrease to maintain acceptable engine performance. The ECM performs this compensation by:

• Increasing the injector pulse width to maintain the required amount of fuel supply
• Increasing idle speed to increase generator output voltage

Fuel cut-off mode

The ECM can completely disable all or some of the injectors under certain conditions. Injector disablement modes allow the ECM to protect the engine from damage and improve vehicle performance.

The ECM disables all six injectors under the following conditions:

• Ignition Off - Prevents the engine from continuing to run after the ignition is turned off
• Ignition On But No Crankshaft Position Sensor Signals - Prevents Flooding or Backfire
• High Engine RPM - Above Redline
• High vehicle speed - Above tire speed rating
• Closed Throttle Braking - Reduces emissions and improves engine braking.

The ECM selectively disables the injectors under the following conditions:

• Torque control is engaged - Gear shifting or dangerous maneuvers.
• Traction control is on - When front brakes are applied

Description of the fuel vapor recovery system (FVRS)

Operation of the fuel vapor recovery system

The fuel vapor recovery system limits the emission of fuel vapor into the atmosphere. Fuel vapor in the fuel tank exits the fuel tank through the vapor line into the EVAP canister. The carbon in the canister absorbs and stores the fuel vapor. Excess pressure is released through the vent line into the atmosphere. The fuel vapor is stored in the EVAP canister until the engine is able to use it. At the appropriate time, the control module commands the EVAP canister purge valve to open, and the canister is connected to the engine intake manifold vacuum. Clean air is sucked into the canister, removing the fuel vapor from the carbon. The air and fuel mixture passes through the purge tube and the EVAP purge valve into the intake manifold and is consumed in the normal combustion mode.

Fuel Evaporative System Components

The fuel vapor recovery system consists of the following components:

Adsorber

The canister is filled with carbon granules that absorb and store fuel vapors. The fuel vapors are stored in the canister until the control module determines that the vapors can be used up in the normal combustion process.

Evaporative canister purge valve.

The purge valve of the adsorber controls the supply of vapors from the SUMP system to the intake manifold. The control module supplies this normally closed valve with a pulse-width modulated control voltage, precisely regulating the flow of fuel vapors into the engine. This valve also opens at certain points during the fuel vapor capture system check to supply the system with vacuum from the engine's intake manifold.

Description of the electronic ignition system

The electronic ignition system creates and maintains a powerful secondary spark. The spark ignites the compressed fuel-air mixture at a precisely calculated moment in time. This ensures optimal engine operation, fuel economy and reduced exhaust emissions. The ignition system has a separate ignition coil for each cylinder. The ignition coils are installed in the middle of each valve cover; the coils are connected to the spark plugs by short integral connector caps. The ECM switches the control keys in the ignition coils on and off. The ECM takes into account engine speed, the signal from the mass air flow sensor, and the signals from the camshaft and crankshaft position sensors. Based on this data, the sequence, duration, and timing of the sparks are calculated. The electronic ignition system consists of the following components:

Crankshaft Position Sensor (CKP)

The crankshaft position (CKP) sensor communicates with a sensor rotor located on the crankshaft and having 58 teeth. The ECM monitors the voltage between the signal circuits of the CKP sensor. As each tooth passes the sensor, the sensor generates an analog signal. These analog signals are sent to the ECM for processing. The angle between the sensor teeth is 6 degrees. Since there are only 58 teeth, there is a gap of 12 degrees in which there are no teeth. This creates a characteristic pulse train that allows the ECM to determine the position of the crankshaft. Based on the CKP signal alone, the ECM can determine which pair of cylinders is approaching top dead center. The signals from the camshaft position sensors help determine which of the two cylinders is in the power stroke and which is in the exhaust stroke. Based on this data, the ECM accurately synchronizes the ignition system, fuel injectors and the knock control system. This sensor is also used to detect misfires.

Camshaft Position Sensor (CMP)

The engine uses 4 camshaft position sensors (SMRs), one for each camshaft. The camshaft position sensor signal is a digital logic pulse signal generated 4 times for each camshaft revolution. The camshaft position sensor does not directly affect the operation of the ignition system. The camshaft position sensor information is used by the ECM controller to determine the position of 4 camshafts relative to the crankshaft. By monitoring the camshaft and crankshaft position sensor signals, the ECM controller can precisely control the fuel injector actuation moments. The ECM controller supplies the camshaft position sensor with a 5 V reference voltage circuit and a low-level reference voltage circuit. Camshaft position sensor signals are sent to the ECM controller inputs. They are also used to determine the position of camshafts relative to the crankshaft.

Ignition coils

Each ignition coil contains a semiconductor switch, which is the main element of the coil. The ECM initiates the spark by applying voltage through the ignition control circuit to the ignition coil switch for a certain amount of time (closing time). When the voltage is removed, the coil produces a spark in the spark plug. The following circuits are connected to the ignition coils:

• Ignition Voltage Circuit 1
• Ignition control circuit
• Two grounding circuits

Electronic Engine Management System (EEMS) Controller

The ECM controls all ignition system functions and continually adjusts ignition timing. The ECM monitors information from a variety of sensors, including the following:

• Throttle Position (TP) Sensor Signal
• Engine Coolant Temperature (ECT) Sensor Signal
• Mass Air Flow (MAF) Sensor Signal
• Intake Air Temperature (IAT) Sensor
• Vehicle Speed Sensor (VSS) Signal
• Gearbox position or range sensors
• Engine knock sensors (KS)
• Barometric pressure sensor (BARO)

Description of the knock sensor system

All sensors and most input circuits can be diagnosed with a scan tool. This section provides brief instructions on how to use a scan tool to diagnose input circuits where possible. The scan tool can also be used to compare parameters of a normally running engine with those of the engine being diagnosed.

The knock sensor (KS) system detects engine knock. Based on the signals from the knock sensor system, the ECM retards spark. The knock sensor produces an alternating voltage signal that is sent to the ECM. The voltage is proportional to the intensity of the knock.

The ECM monitors the voltage of the post-ignition sensors in each cylinder.

If detonation occurs in any of the cylinders, the ignition timing for that cylinder is delayed. If detonation disappears, the ignition timing gradually returns to the previous timing.

If detonation in the same cylinder continues despite ignition retardation, the ECM increases the retardation in steps, up to a maximum of 12 degrees. Ignition is also retarded at high temperatures to counteract the tendency for detonation at high intake air temperatures.

If the sensor of the 1st or 2nd row does not work or there is a problem with the internal circuit, the ignition is carried out according to the default circuit. The default circuit provides the maximum allowable ignition delay to protect the engine from possible damage.

Description of the air intake system

The mass air flow sensor measures the amount of air entering the engine. Direct measurement of air flow provides greater accuracy than estimates based on other sensors. The mass air flow sensor also houses an integrated intake air temperature (IAT) sensor. The following circuits are connected to the mass air flow sensor:

• Ignition Voltage Circuit 1
• 5V Reference Voltage Circuit
• Low Voltage Reference Circuit
• Signal chain
• IAT signal chain

This vehicle uses a hot-film mass air flow sensor. The output voltage of the mass air flow sensor depends on the power required to maintain the temperature of the sensing element at a specified level above the ambient temperature. Air passing through the sensor cools the sensing elements. The intensity of cooling is proportional to the air flow. The greater the air flow, the greater the current required to maintain the heated film at a constant temperature. The mass air flow sensor converts the current into a voltage signal, which is monitored by the ECM. The ECM uses this signal to calculate the air flow.

The ECM monitors the MAF sensor signal voltage and can determine if the sensor voltage becomes too low. The ECM can also determine from the sensor voltage that the air flow is not appropriate for a specific operating mode.

The scan tool displays the mass air flow value in grams per second (g/s). The value should change fairly quickly under acceleration, but remain stable at constant engine speed. If the ECM detects a malfunction in the mass air flow sensor circuits, the following DTCs are set:

• P0101 Mass Air Flow (MAF) Sensor Performance
• P0102 Mass Air Flow (MAF) Sensor Circuit Low Voltage
• P0103 Mass Air Flow (MAF) Sensor Circuit High Voltage

Intake Manifold Runner Control (IMRC) Solenoid Valve

The torque characteristic of an engine with normal air supply depends mainly on how the average pressure in the engine changes over the range of engine operating speeds. The average pressure is proportional to the volume of air in the cylinder at the moment the intake valve closes. The mass of air sucked into the cylinder at a given engine speed is determined by the design of the intake system.

The Intake Manifold Runner Control (IMRC) valve (2) changes the position of the intake manifold chamber baffle. When the IMRC valve is open, the intake manifold is one large chamber (4). When the IMRC valve is closed, the intake manifold is converted into two smaller chambers (3). The two positions of the intake manifold baffle correspond to two torque characteristics, which improves engine performance at low and high speeds. The IMRC valve is located in the intake manifold (1). Ignition voltage 1 is applied to the IMRC valve solenoid; the solenoid is controlled by the ECM.