Description of the fuel system

Fuel tank

The fuel tank is made of high density polyethylene. The fuel tank is fixed with 2 metal clamps, which are attached to the bottom of the car body. The fuel tank is recessed to maintain a constant supply of fuel around the strainer at low fuel levels and during sharp manoeuvres.

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

Fuel filler neck

To avoid refueling with leaded fuel, the fuel filler neck has a built-in restrictor and deflector. Only the thinner unleaded fuel nozzle will fit into the restrictor opening, which must be fully inserted to bypass the deflector. When refueling, the tank is vented through a vent tube located inside the fuel filler neck.

Fuel filler cap

Note: If replacement is necessary, use a fuel filler cap with the same specifications. Using the wrong type of fuel filler cap can cause serious problems with the fuel system.

The fuel filler cap has a ratchet vent screw to prevent over tightening.

The vent action allows the fuel tank to be depressurized before the cap is removed. Instructions for use are printed on the neck cap. The cover has a safety vacuum valve.

Fuel module

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

• Maintain the optimum fuel level in the built-in fuel tank at all levels of fuel in the tank and while driving.
• Improve the accuracy of measuring the fuel level 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

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

• First stage fuel pump through external strainer and/or
• secondary umbrella valve or
• fuel return 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 through the fuel pump relay.

Fuel module strainers

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

• Filtration of contaminants
• Separation of water from fuel
• Creating a capillary effect that promotes the suction of fuel into the fuel pump

Stopping the flow of fuel through the strainer indicates that there is too much sediment or water in the fuel tank. In this case, the fuel tank must be removed and washed, and the strainer 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 the in-line fuel filter to the fuel injection system. The fuel pressure regulator maintains a regulated fuel pressure to the fuel injectors. Unused fuel is returned from the fuel filter to the fuel tank via a separate fuel return line. Paper filter element (2) traps particles in the fuel that can damage the fuel injection system. Filter housing design (1) allows it to withstand the 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.

Evaporative Emissions Pipelines and Hoses

The evaporative emission system pipeline runs from the fuel tank vent valve to the evaporative emission system adsorber and on to the engine compartment. The EVAP tubing is made of nylon and is connected to the EVAP canister with a quick coupler.

Fuel pressure control

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

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 pressure set in the system and the pump turned off, the pressure should stabilize and be maintained. If the pressure regulator keeps the fuel pressure too low or too high, the vehicle's drivability will be adversely affected.

Fuel rail

The fuel rail consists of 3 parts:

• Pipes delivering fuel to all injectors
• Fuel pressure ports
• Six independent fuel injectors

The fuel rail is mounted 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, the normally closed ball valve opens to allow fuel mixture through the guide plate to the injector outlet. The guide plate has holes that control the flow of fuel and form a double cone of finely atomized fuel at the nozzle exit. The fuel flow from the injector outlet is directed to both intake valves. As a result, before entering the combustion chamber, the fuel is additionally evaporated.


Fuel injector problems can cause a variety of vehicle drivability problems. The following types of problems are possible:

• Nozzles do not open
• Nozzles stuck open
• Nozzles are leaking
• Injector windings have low resistance

Fuel pump relay

The ECM controls the operation of the fuel pump through the fuel pump relay. The ECM energizes the fuel pump relay whenever it detects crankshaft position sensor pulses.

Fuel supply to the engine

Fuel is supplied to the engine through six separate fuel injectors, one for each cylinder, controlled by the ECM. The ECM controls the injectors by applying a short pulse of current to the injector coil every second engine revolution. The duration of this short pulse is carefully timed by the ECM to deliver just the right amount of fuel for good engine performance and reduced emissions. The time that the nozzle is open is called the pulse width and is measured in milliseconds (thousandths of a second). While the engine is running, the ECM constantly monitors the signals 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 time, the desired air-fuel ratio and the actual mass of air in each cylinder are taken into account; a correction for battery voltage, short-term and long-term fuel trim are also introduced. The calculated impulse is applied at the moment of closing the inlet valves of the cylinder in order to ensure maximum evaporation duration and efficiency.


The fuel supply when starting with a starter is slightly different from the supply when the engine is running. At the beginning of the rotation of the motor, an initiating pulse can be given to accelerate the start. As soon as the ECM determines which phase of the ignition sequence the engine is in, the ECM starts pulsing the injectors. The pulse width when starting with the starter depends on the temperature of the coolant and the engine load. The fuel system has a number of automatic adjustments to compensate for variation in fuel system components, driving conditions, fuel used and vehicle aging. The heart of fuel control is the pulse width calculation process described above. The calculation takes into account the correction for battery voltage, as well as short-term and long-term fuel adjustments. Correction for battery voltage is necessary because the voltage at the injector affects the throughput of the injector. Short-term and long-term fuel trims are fine and coarse adjustments to pulse width for best engine performance and reduced emissions. These corrections are calculated based on feedback from the oxygen sensors in the exhaust gas stream and are applied only if the fuel supply system is operating in closed loop mode.

In some situations, the fuel supply system turns off the injectors for a certain time. This is called a fuel cut. Fuel cut is used to improve traction, save fuel, reduce emissions, and protect the vehicle in certain extreme or adverse situations.

If a significant internal problem occurs, the ECM can switch to a backup fuel strategy (low power mode), which will keep the engine running until maintenance is carried out.

Sequential fuel injection (SFI)

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

The ECM has several fuel control modes based on information from the sensors.

Start mode

When the ECM 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 then uses signals from the MAF sensors, intake air temperature, engine coolant temperature, and throttle position to determine the required pulse width for starting.

Free flow mode

If the engine chokes on fuel at start-up and does not start, you can manually select the flood recovery mode. To enter the anti-flooding mode, you must press the accelerator pedal to the fully open position. This causes the ECM to fully disable the injectors and maintains this state as long as the ECM sees the throttle fully open at engine speeds below 1000 rpm.

Driving mode

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

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

Acceleration mode

The ECM monitors changes in throttle position and mass air flow sensors to determine when the vehicle is in acceleration mode. In this case, the ECM increases the injector pulse width to increase fuel delivery and improve engine performance.

Braking mode

The ECM monitors changes in 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 drop in battery voltage, it can compensate for the drop in order to maintain acceptable engine performance. The ECM implements this compensation by:

• Increasing the pulse width of the injectors to maintain the correct amount of fuel
• Increase idle speed to increase generator output voltage

Fuel cut mode

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

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 backfiring
• High engine speed - Above redline
• High vehicle speed - Above rated tire speed
• Closed throttle braking - Reduces emissions and improves engine braking.

The ECM selectively disables the injectors under the following conditions:

• Torque control engaged - Shifting gears or dangerous manoeuvres.
• Traction control engaged - Front brake applied

Description of the Evaporative Emission System (SUPS)

Evaporative Emission System Operation

The EVAP system limits the emission of fuel vapors into the atmosphere. The fuel vapors in the fuel tank leave the fuel tank through the steam line to the ESU adsorber. The coal with which the adsorber is filled absorbs and accumulates fuel vapors. Excess pressure is released through the vent pipe to the atmosphere. Fuel vapors are stored in the EVAP canister until the engine is able to use them. At the right moment, the control module commands the canister purge valve to open, and the canister is connected to the engine intake manifold vacuum. Clean air is sucked into the adsorber, which removes fuel vapors from coal. The air/fuel mixture passes through the EVAP purge tube and purge valve into the intake manifold and is consumed during normal combustion.

Evaporative Emission System Components

The fuel vapor recovery system consists of the following components:

Adsorber

The adsorber is filled with coal granules, which absorb and accumulate 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.

Canister purge valve.

The canister purge valve controls the supply of vapor from the EVAP system to the intake manifold. The control module applies a pulse-width modulated control voltage to this normally closed valve to precisely control the flow of fuel vapor into the engine. This valve also opens at some points in the evaporative emission system test to apply vacuum to the system from the engine intake manifold.

Description of the electronic ignition system

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

Crankshaft position sensor (CKP)

crankshaft position sensor (CKP) interacts with the sensor rotor located on the crankshaft and having 58 teeth. The ECM monitors the voltage between the CKP sensor signal circuits. As each tooth passes by the sensor, the latter generates an analog signal. These analog signals are sent to the ECM for processing. The angle between the teeth of the sensor is 6 degrees. Since there are only 58 teeth, there is a gap of 12 degrees with 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 make it possible to determine which of these two cylinders is in the power stroke and which is in the exhaust stroke. Based on this data, the ECU performs precise synchronization of the ignition system, fuel injectors and anti-knock system. This sensor also serves to detect misfires.

Camshaft position sensor (SMR)

The engine uses 4 camshaft position sensors (SMR), one for each camshaft. The camshaft position sensor signal is a digital logic pulse signal generated 4 times per 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 to determine the position of the 4 camshafts relative to the crankshaft. By monitoring the signals from the camshaft and crankshaft position sensors, the ECM can precisely control the firing timing of the fuel injectors. The ECM provides the camshaft position sensor with a 5 V reference circuit and a low voltage reference circuit. The signals from the camshaft position sensors are fed to the inputs of the ECM. They are also used to determine the position of the camshafts in relation to the crankshaft.

Ignition coils

Each ignition coil contains a semiconductor key, which is the main element of the coil. The ECM initiates a spark by applying voltage to the ignition coil key through the ignition control circuit 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 ground circuits

Electronic engine management controller (ECM)

The ECM controls all functions of the ignition system and constantly corrects ignition timing. The ECM monitors information from various sensors, including the following:

• Throttle Angle Sensor Signal (TP)
• Engine coolant temperature sensor signal (EATING)
• Mass air flow sensor signal (MAF)
• Intake air temperature sensor (IAT)
• Vehicle speed sensor signal (VSS)
• Transmission Position or Gear 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 the scan tool to diagnose input circuits where possible. The scan tool can also compare the parameters of a normally running engine with those of a diagnosed engine.

knock sensor system (KS) detects detonation in the engine. Based on signals from the knock sensor system, the ECM delays spark delivery. The knock sensor generates an AC voltage signal that is sent to the ECM. The magnitude of the voltage is proportional to the intensity of the detonation.

The ECM monitors the sensor voltage after ignition in each cylinder.

If any of the cylinders is knocking, the ignition timing for that cylinder is delayed. If at the same time the detonation disappears, the ignition gradually returns to the previous moment.

If detonation continues in the same cylinder despite the ignition delay, the ECM increments the delay, up to a maximum of 12 degrees. Ignition is also delayed at high temperatures to counteract knocking tendencies at high intake air temperatures.

If the bank 1 or 2 sensor fails or there is a problem with the internal circuitry, the ignition will proceed to the default circuit. The default scheme provides for the maximum allowed 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 the air flow is more accurate than calculated data from other sensors. The mass air flow sensor also houses an integrated intake air temperature sensor (IAT). The following circuits are connected to the mass air flow sensor:

• Ignition voltage circuit 1
• 5 V reference circuit
• Low voltage reference circuit
• Signal circuit
• IAT signal circuit

This vehicle uses a heated 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 predetermined level above the ambient temperature. The air passing through the sensor cools the sensing elements. The cooling intensity is proportional to the air flow. The greater the air flow, the greater the current required to keep the heated film at a constant temperature. The mass air flow sensor converts the current into a voltage signal that the ECM monitors. The ECM calculates the air flow based on this signal.

The ECM monitors the MAF sensor signal voltage and can determine if the sensor voltage is getting too low. The ECM can also determine from the sensor voltage that the air flow is not appropriate for a particular mode of operation.

Scan tool outputs Mass Air Flow in grams per second (g/s). The value should change fairly quickly in acceleration mode, but remain stable at constant engine speed. If the ECM detects a malfunction in the mass air flow sensor circuits, the following DTCs will set:

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

Solenoid valve for changing the geometry of the intake manifold (IMRC)

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

Valve (2) intake manifold geometry control (IMRC) changes the position of the baffle of the intake manifold chamber. With the IMRC valve open, the intake manifold is one large chamber (4). When the IMRC valve closes, the intake manifold becomes two smaller chambers (3). 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). The IMRC valve solenoid is supplied with ignition voltage 1; the solenoid is controlled by the ECM.