The system of fuel injection (MFI)

Overview

The system of fuel injection (MFI) consists of sensors which determine the characteristics of the engine, the engine control unit (PCM) that controls the actuators on the basis of information received from the sensors. PCM controls the fuel injection, air supply when the engine is idling and adjusts ignition timing.

In addition, PCM is equipped with several diagnostic functions that facilitate troubleshooting.

Fuel injector

Office opening time of fuel injectors should be carried out so as to constantly maintain an optimum air-fuel ratio, ensuring the performance of the engine.

Each inlet channel running one fuel injector. Fuel under pressure is supplied from the fuel tank by the fuel pump, its pressure is adjusted with a pressure regulator. Further, fuel under a predetermined pressure is distributed to each fuel injector. Fuel is injected into each cylinder once for every two revolutions of the crankshaft.

PCM enriches the fuel-air mixture, make adjustments on the "open loop" to support the work of the cold engine or the engine is running under high load. Further, if the engine is warm or running under normal operating conditions, controls the PCM signals on the mixture heated oxygen concentration sensor "open loop" to keep the proportion of the theoretical air-fuel ratio for maximum exhaust gas purification three-way catalytic converter.

Adjust the engine speed to idle

Engine speed at idle is maintained by adjusting the air supply, carried out through the valve of the throttle assembly in accordance with changing conditions and engine load at idle. PCM controls the engine idle speed adjustment (ISC) and supports the vehicle engine at a preset rotation speed of the crankshaft depending on the coolant temperature and the air conditioning load. When the air conditioner is switched off and the engine is idling the engine ISC regulates the flow of air passing through the throttle valve assembly, so as to prevent fluctuations in the rotational speed of the engine crankshaft.

Adjust the ignition timing

The switch controls the ignition timing in order to ensure its

the optimum value in accordance with engine operating conditions. Ignition timing is determined by the PCM, depending on the speed of the crankshaft of the engine, the volume supplied to the engine air, coolant temperature and atmospheric pressure.

Additional management features

1. The fuel pump control.

The inclusion of the fuel pump relay supplies DC power to the fuel pump at start-up and operation of the engine.

2. Management of compressor clutch relay.

The relay switches on and off the air conditioning compressor clutch.

3. Management of the radiator fan relay.

Speed radiator fan and condenser are changing in accordance with the coolant temperature and vehicle speed.

4. Management EVAP.

Diagnostic mode

When a fault occurs in one of the sensors or actuators to warn the driver warning lamp ?�Check engine?�.

When a fault is detected in one of the sensors or actuators on the output appears DTC.

DTC recorded in the RAM memory in the ECM referring to the sensors and actuators can be read by a scanner.

Most faults occur periodically occurring under certain conditions. The identification of these conditions will make it easier to determine the cause of the fault.

Eliminating periodic faults

Ask faults.

Ask how the problem manifests itself in view of operating conditions, weather conditions, the frequency of failure, and so on. D.

Determine the appearance of a fault condition.

Normally, almost all periodic faults appear in vibration, temperature fluctuations and / or changes in humidity, and as a result of unreliable connections in connectors.

Use the simulation test.

When vibration or abuse connections connectors using simulation tests below. Determine the best possible chain (s) and run tests on the connectors and elements of the chain (s). Make sure to use inspection operations listed for diagnostic codes and the cause of the failure.

At periodic faults associated with changes in temperature and / or humidity, try to change the conditions of suspected elements of the chain, then use the simulation tests.

Ensure that the detected fault is intermittent.

Correct the problem and try again to duplicate the conditions that led to a failure to ensure that the periodic fault has been rectified.

Simulation tests.

If simulation test simulation pull, fold, twist and pull the wiring of each of the elements to determine the place of the periodic fault:

- Shake the connector up and down, left and right;

- Shake the wiring harness up and down, left and right;

- Create some element or vibration sensor.

Service points at check fuse

Remove the fuse and measure the resistance between the load side of the blown fuse, and "weight". Turn on all circuits connected to this fuse.

If the resistance is almost zero, there is a short circuit between these switches and the load. If the resistance is not zero, it means that there is no short circuit, and the fuse has blown due to a short circuit.

The main causes of short circuit:

- Harness pinched the car body;

- Damaged outer winding wire harness as a result of grinding or heating;

- The socket or the electrical circuit is exposed to water;

- Random error (erroneous Circuit, and so on. D.).

Inspections of MFI

If MFI components (sensors, PCM, etc. nozzles. D.) Fail, broken supply quantity of fuel into the respective cylinders of the engine at different operating conditions, which leads to the following:

- The engine starts with difficulty or not at all starts;

- Unstable work of the engine idling;

- Unstable operation of the engine in all modes.

When any of these states, first perform basic checks of the engine (ignition engine settings and the like. D.), And then check the components of the MFI.

On-board diagnostics

Diagnostic trouble codes are stored in memory in the following cases:

- After the first time the PCM detects a fault, a DTC is recorded when the same error occurs when restarting the engine;

- When misfiring when enriched or depleted fuel mixture DTC is recorded at the first fault detection.

DTCs are erased from the PCM memory in the following cases:

- After recording the DTC, if PCM is not re-detects a fault within 40 driving cycles;

- When misfiring if rich or lean fuel mixture when the following two conditions:

- Driving conditions (engine speed of the engine, coolant temperature, and so on. D.) Are identical to those for which the first was recorded by the fault;

- When PCM is not re-defines the fault within 80 driving cycles.