6.11. Control system of the MFI engine

Placement of elements of a control system of MFI

1 – measuring instrument of a consumption of OBD air;
2 – the sensor of temperature of the air coming to the engine;
3 – the air consumption measuring instrument, except "OBD";
4 – the sensor of fuel-air mix, except "OBD";
5 – sensor of temperature of cooling liquid;
6 – sensor of provision of a butterfly valve;
7 – sensor of position of the camshaft;
8 – sensor of an angle of rotation of a bent shaft;
9 – the warmed oxygen sensor;
10 – fuel nozzles;
11 – idling frequency modulator;
12 – car speed sensor;
13 - detonation sensor;
14 – switch of ranges of the transmission;
15 - ignition lock;
16 – control unit of the ESM engine;
17 – relay of the air conditioning system;
18 – the electromagnetic valve of cleaning of a canister with absorbent carbon;
19 – main MFI relay;
20 – ignition coils;
21 – fuel pump;
22 – acceleration sensor;
23 – diagnostic socket.

Control of fuel system is exercised of the control unit of the ESM engine (Engine Control Module). The ESM block carries out adjustment of a corner of an advancing of ignition, defines amount of the fuel given to the engine, operates system of decrease in toxicity of the fulfilled gases and frequency of rotation of a bent shaft of the engine idling, and also coupling of the compressor of the conditioner, etc. The ESM block changes power setting depending on the changing operational modes on the basis of signals from various switches and sensors.

For example, the ESM block regulates an ignition advancing corner on the basis of signals of sensors which react to the frequency of rotation of a bent shaft, temperature of cooling liquid, the provision of the butterfly valve included at present in transfers, car speed, etc.

The ESM block regulates the frequency of rotation of a bent shaft of idling on the basis of signals of sensors which react to the provision of a butterfly valve, the car speed included at present in transfer, etc.

The sensor of the measuring instrument of a consumption of OBD air (MAF – Mass Airflow Sensor)

The measuring instrument of a consumption of air provides the most direct method to measure engine loadings as it measures amount of the air coming to the engine. The stream of air comes to the engine via the measuring instrument with the heated and cold wire elements forming a part of the bridge scheme. The current passing through a heated wire element maintains its constant temperature at the constant level which is higher, than temperature of the air coming to the engine. The mass of air is determined by the current necessary for maintenance of temperature of a wire element. The more a stream of air and, naturally, its cooling, the more size of the signal given on the ESM block.

The sensor of temperature of the OBD air coming to the engine (IAT – intake air temperature)

The sensor of temperature of the air coming to the engine represents a thermistor which resistance changes depending on temperature. The ESM block considers a signal of the sensor and corrects width of the impulse given on nozzles therefore the amount of the fuel given to engine cylinders changes and also changes an ignition advancing corner.

Check of the sensor

PERFORMANCE ORDER
1. Measure tension between contacts 1 and 3 sockets of the sensor.
Temperature
Output tension
0 °C
3,3-3,7 B
20 °C
2,4-2,8 B
40 °C
1,6-2,0 B
80 °C
0,5-0,9 B
2. If the output tension of the sensor differs from demanded, replace the sensor.

The sensor of absolute pressure in an inlet collector, except "OBD" (MAF – Manifold Absolute Pressure)

The sensor of absolute pressure in an inlet collector represents the sensitive variable resistor. It measures pressure in an inlet collector which changes depending on the operational modes of the engine and is transformed to tension. The sensor is also used for measurement of atmospheric pressure at start of the engine and provides power setting at different heights above sea level. On the basis of information from the sensor the control unit of the engine regulates amount of the fuel given to the engine, and also changes an ignition advancing corner.

Check

PERFORMANCE ORDER
1. Measure tension between contacts 1 and 4 sockets of the sensor.

Output tension at the included ignition and the idle engine: 4–5 V
Output tension at an idling frequency: 0,5-2,0 B

2. If the output tension of the sensor differs from demanded, replace the sensor.

The sensor of temperature of the air coming to the engine (IAT – intake air temperature)

The sensor of temperature of the air coming to the engine represents a thermistor which resistance changes depending on temperature. The ESM block considers a signal of the sensor and corrects width of the impulse given on nozzles therefore the amount of the fuel given to engine cylinders changes and also changes an ignition advancing corner.

Check

PERFORMANCE ORDER
1. Measure resistance between contacts 1 and 2 sockets of the sensor.
Temperature
Resistance
0 °C
4,5–7,5 Ohm
20 °C
2,0–3,0 Ohm
40 °C
0,7–1,6 Ohm
80 °C
0,2–0,4 Ohm
2. If resistance of the sensor differs from demanded, replace the sensor.

The sensor of temperature of cooling liquid (ECT – Engine Coolant temperature)

The sensor of temperature of cooling liquid controls temperature of cooling liquid and on the basis of a sensor signal the ESM block calculates width of the impulse given on nozzles therefore the amount of the fuel given to engine cylinders changes and also changes an ignition advancing corner.

On the cold engine the ESM block works in the mode of an open loop therefore in cylinders of the engine richer toplivnovozdushny mix moves and idling rotation frequency increases. It proceeds before achievement by the engine of normal working temperature.

Removal

PERFORMANCE ORDER
1. Remove the sensor from the engine.
2. Heating a vessel with water and the sensor located in it, check its resistance.
Temperature
Resistance
– 30 °C
22,22–31,78 kOhm
– 10 °C
8,16–10,74 kOhm
0 °C
5,18–6,60 kOhm
20 °C
2,27–2,73 kOhm
60 °C
1,059–1,281 kOhm
40 °C
0,538–0,650 kOhm
80 °C
0,298–0,322 kOhm
90 °C
0,219–0,243 kOhm
3. If resistance of the sensor differs from demanded, replace the sensor.

Installation

PERFORMANCE ORDER
1. Apply LOCTITE 962T sealant on a sensor carving.
2. Screw the sensor in the block of cylinders and tighten it the required moment.

Inhaling moment: 15–20 N • m

3. Connect the electric socket to the sensor.

The sensor of provision of a butterfly valve (TP – Throttle Position)



The sensor of provision of a butterfly valve transfers information on the basis of which the ESM block defines when the butterfly valve is closed, completely open or is in intermediate positions. The sensor is rigidly connected to shaft of a butterfly valve. Depending on the provision of a butterfly valve sensor resistance changes. For power supply of the sensor from the ESM block on it tension of 5 Century moves. The output tension of the sensor changes from 0,25 B at the minimum opening of a butterfly valve to 4,7 B at full opening of a butterfly valve.

Check


PERFORMANCE ORDER
1. Disconnect the socket from the sensor of provision of a butterfly valve.
2. Measure resistance between contacts 1 and 2 sockets of the sensor.

Resistance: 0,7–3,0 kOhm

3. Connect an ohmmeter to contacts 1 and 3 sockets of the sensor.
4. Slowly open a butterfly valve and be convinced that sensor resistance smoothly changes in proportion to opening of a butterfly valve.
5. If resistance of the sensor differs from demanded or changes in steps, replace the sensor.

Inhaling moment: 1,5–2,5 N • m


The sensor of position of the camshaft (CMP – Camshaft Position Sensor)


The sensor of position of the camshaft develops impulses on the basis of which the ESM block identifies the first cylinder and time of opening of a nozzle.

The sensor of an angle of rotation of a bent shaft (CKP – Crankshaft Position Sensor)


The sensor of an angle of rotation of a bent shaft transfers to the ESM block information on the provision of a bent shaft. On the basis of information of an output signal of this sensor and a signal of the sensor of position of the camshaft the ESM block defines a corner of an advancing of ignition and the cylinder to which it is necessary to give fuel. In the absence of output signals of the sensor the engine will not be started.

Check

PERFORMANCE ORDER
1. Disconnect the socket from the sensor of an angle of rotation of a bent shaft
2. Measure resistance between contacts 1 and 2 sockets of the sensor.

Resistance: 0,486–0,594 kOhm at 20 °C

3. If resistance of the sensor differs from demanded, replace the sensor.

Gap between a rotor and the sensor of an angle of rotation of a bent shaft: 0,5–1,0 mm
Inhaling moment: 9–11 N • m


Oxygen sensor


Depending on the content of oxygen in the fulfilled gases the sensor of oxygen induces tension from 0 to 1 Century. On the basis of these data the control unit of the engine changes time of opening of nozzles and a ratio of fuel in toplivnovozdushny mix. In order that there was a full combustion of gas mixture and in the fulfilled gases there were no harmful substances, 1 part of fuel has to fall on 14,7 weight parts of air.

The sensor of oxygen is equipped with a heater which maintains sensor temperature in a certain interval during the operation of the engine on all operational modes. Maintenance of a certain temperature of the sensor allows system to get quicker into gear and to work in the idling mode.

Check

PERFORMANCE ORDER

Prevention

Before check warm up the engine until temperature of cooling liquid is not equal to 80-95 °C.
Measure by the exact digital voltmeter the output tension of the sensor.


If the output tension of the sensor differs from demanded, replace the sensor.

Inhaling moment: 50–60 N • m


Fuel nozzles


Fuel nozzles on the basis of signals from the ESM block inject fuel into engine cylinders. The amount of the given fuel depends on time of the opening of nozzles, i.e. from width of an impulse of tension given on a nozzle winding.

Check

PERFORMANCE ORDER
1. During the operation of the engine idling a stethoscope or a finger of a hand check work of nozzles on existence of clicks.
2. If clicks are absent, check reliability of connection of sockets to nozzles and the output tension of the control unit.
3. Disconnect the socket from a fuel nozzle and measure resistance between contacts of the socket.

Resistance: 15,9± 0,35 Ohms
4. Connect the socket to a fuel nozzle.

Detonation sensor


The sensor of a detonation reacts to high-frequency fluctuations of the block of cylinders and transforms them to electric signals which size increases at increase in a detonation. On the basis of these signals the ESM block displaces the ignition moment towards delay therefore the detonation is eliminated.

Fuel pipelines and hoses

Fuel pipelines and hoses provide transfer of fuel from the fuel tank to the fuel highway and nozzles and return excess fuel in a tank. The fuel pipelines fixed on the car bottom need to be examined periodically on lack of dents and deformation as due to narrowing of their passes restriction of a stream of fuel is possible.
Fuel pipelines and hoses also provide transfer of vapors of fuel from the fuel tank to a canister with absorbent carbon where they gather at the switched-off engine. After launch of the engine and warming up up to the working temperature the control unit of the engine opens the electromagnetic valve, and fuel vapors from a canister come to the engine and are burned.