When driving in urban conditions, up to a quarter of the time the engine runs in forced mode. idle move. This occurs when engine braking, gear shifting, vehicle coasting, etc. In these modes, the throttle valve of the carburetor is closed (the throttle control pedal is fully released), the engine speed exceeds the speed of its independent idling.

On forced idle crankshaft the engine rotates due to the kinetic energy of the car. The vehicle is in gear and the throttle pedal is released, so the engine is wasting fuel without doing any useful work. In forced idle mode, no power is required from the engine, and the combustion of the combustible mixture leads only to pollution environment. As a result of the rapid closure throttle valve combustible mixture enriched and the toxicity of exhaust gases increases.

To reduce fuel consumption, reduce the toxicity of exhaust gases on trucks and cars, electronic systems for automatic control of the forced idle economizer (EPKhK) are used. EPHH is designed to stop the supply of fuel in the forced idle mode.

Into the system automatic control EPHH is included the electronic unit control, solenoid valve and carburetor limit switch (microswitch, screw sensor, etc.).

Forced idle mode is distinguished by two features:

1) speed crankshaft engine more frequency at idle;

2) The carburetor throttle is closed.

Shutting off the fuel supply at forced idle (PXH) is carried out using the solenoid valve installed in the carburetor cover on the idle fuel jet. The current supply to the solenoid valve coil is controlled by electronic device- EPHX control unit connected in electrical circuit with solenoid valve, power supply, ignition coil, throttle position sensor on the carburetor, and vehicle ground.

PXX mode is coming (he has different engines correspond to different speeds and throttle closing) when the EPHX control unit registers the simultaneous presence of the above two signs. After the end of the PHX mode, when the throttle valve opens and the shaft speed increases due to the operation of the main dosing system of the carburetor, when a certain crankshaft speed is reached, the EPXH electronic control unit gives a control signal to the solenoid valve. The fuel supply begins through the carburetor idle system.

On fig. 3.3. a block diagram of the automatic control system EPHH is presented.

Rice. 3.3. Structural diagram of the EPHH automatic control system

Current pulses from the ignition coil 2 (Fig. 3.4) provide information about the speed, and the throttle position sensor, which is the carburetor limit switch (sensor-screw EPHKh) 5, mechanically closed to ground when the throttle is fully closed (gas pedal ” is released), signals the transition of the carburetor to the PXX mode. When the “gas” pedal is depressed (the switch is open), the solenoid valve 4 is turned on regardless of the crankshaft speed. Power is supplied to the control unit 3 only when the ignition is on, therefore, when the ignition is turned off, the solenoid valve is simultaneously turned off (regardless of the position limit switch carburetor).

Rice. 3.4. Scheme of the carburetor solenoid valve control system:

1 - ignition switch; 2 - ignition coil; 3 - EPHX control unit; 4 - solenoid valve; 5 - limit switch of the carburetor (sensor-screw EPHX); A - to power supplies.

The de-energization of the solenoid valve also occurs when the ignition is turned off, which excludes the possibility of engine operation with self-ignition.

Automatic control system EPKhH cargo and cars somewhat differ in the control algorithm, scheme and design. Schematic diagrams of electronic control units EPHH for cars and trucks depend on the control law of the carburetor solenoid valve, i.e. ratio of engine speed and throttle position

In the control unit 50.3761 (see Fig. 3.5), the input signal from the primary winding of the ignition coil is fed to pin 4 of the microcircuit A1. At the output of 3 microcircuits A1 pulses of constant duration are formed, the repetition frequency of which corresponds to the frequency of the input signals (from the chopper). On transistors VT1 And VT2 a key was built, which during the action of the pulse at the input of the microcircuit A1 discharges the timing capacitor C1. In the pause between pulses, the capacitor C1 charged through resistors R1 And R2. The maximum voltage to which the capacitor is charged C1, increases with decreasing signal frequency.

Rice. 3.5. circuit diagram control unit EPHX 50.3761:

A1 And A2- microcircuits; S1- microswitch; 1 - ignition coil; 2 - pneumatic valve; X1, X2, X4, X5, X6- conclusions of the EPHH control unit

On transistors VT3 And VT4 threshold element is built. When the voltage across the capacitor C1 exceeds a reference value of approximately 8 V, these transistors open.

Thus, when the frequency of the input signal decreases below the turn-on threshold, the capacitor C1 manages to charge up to a voltage exceeding the reference value of the threshold element. At the same time, the transistors VT3 And VT4 open and through the microcircuit A2 to the base of the transistor VT6 a signal is given that turns on the transistor VT6 and hence the transistor VT8 and the solenoid valve is energized.

When connecting the plug X5 with "ground" (through the contacts of the throttle position sensor), the input voltage at the solenoid valve varies depending on the frequency at the input. When disconnecting the plug X5 the transistor closes from the "mass" VT7, a transistor VT5 opens. Accordingly, the output transistor opens VT8. In this case, the "+" from the battery is constantly connected to the solenoid valve, regardless of the frequency of the input signal.

In the microprocessor control system for the ignition and EPHH of the ZIL-431410 car, the input of the controller 8 (Fig. 3.6) receives signals from the sensors for the engine crankshaft speed, coolant temperature and throttle position, as well as from the load sensor of the controller, to which from the mixing chamber vacuum is applied to the carburetor. The output controller generates a control signal for the EPHH valves.

At a crankshaft speed of less than 1000 min -1, a coolant temperature of less than 60 0 C, an open throttle valve and a vacuum in the carburetor mixing chamber of less than 520 mm Hg. the controller deactivates the solenoid valves and the engine automatically resumes idling.

At an engine crankshaft speed of more than 1100 min -1, the coolant temperature is more than 60 ° C, the throttle valve is fully closed (the throttle control pedal is released) or the vacuum in the carburetor mixing chamber is more than 560 mm Hg. the controller turns on solenoid valves that block the fuel supply channels to the carburetor idle system (engine braking mode).

Rice. 3.6. Connection diagram microprocessor system ignition control and EPHH:

1 - distributor; 2 - ignition coil; 3 - backup device (vibrator); 4 - switch; 5 - coolant temperature gauge; 6 - electromagnetic EPHH valves; 7 - ignition switch; 8 - controller; 9 - throttle position sensor; 10 - reference point sensor; 11 - sensor of angular impulses; 12 - view of the connector of the angular impulse sensor

The control unit is carried out on a printed circuit board and is located inside a plastic case. To cool the power transistor, a plate is adjacent to it - a heat sink. The plug block is made integral with the cover of the block, which has six slots for the passage of plugs.

7.4.1. Forced idle economizer control system (EPKhK)

Design features

The EPHH system serves to increase the efficiency of the engine and reduce the level of toxicity of exhaust gases. Since the engines mod. 331 and 2106 install carburetors of the same type - "Ozone", their EPHX systems are structurally the same and differ only in the arrangement of carburetor pneumatic valves (see "Power System") and the type of control units that have different characteristics(for engine mod. 331 use control unit 252.3761, mod. 2106-25.3761 or 2533.3761).

The device and operation of the EPHH system are considered on the example of an engine mod. 331. The system contains a control unit 4 (), solenoid valve 5, microswitch 3 and connecting wires. In addition, the system includes a pneumatic valve 7 built into the carburetor.

The principle of operation of the EPHH is that in forced idle modes, the fuel supply to the engine is turned off (in cases where the throttle control pedal is released and the crankshaft speed is higher than the frequency in idle mode). The pneumatic valve 7 EPHH, which is part of the carburetor, turns off the fuel supply. The pneumatic valve is controlled by the solenoid valve 5, which in turn is controlled by the control unit 4 and the microswitch 3.

When checking, pay attention to the condition of the contact connections of all components of the system, their violation can cause interruptions in the operation of the engine.

Design features

The EPHX control unit type 252.3761 () continuously monitors the engine crankshaft speed by measuring the repetition period of the ignition system pulses, which are taken from the ignition coil and fed to output 4 of block 4 (see). At a crankshaft speed less than 1245 min -1 ± 5% (1140 min -1 ± 5% for blocks 25.3761 or 2533.3761), current is supplied to terminals 1 and 2 of the block and passes through the solenoid valve winding, bypassing the microswitch. When the speed increases to 1500 min -1 ± 5%, the electrical connection of terminals 1 and 2 breaks and is restored again only when the engine speed drops to 1245 min -1 (1140 min -1 ).

Checking the EPHX control unit

The control unit is checked on the car. At idle, remove the plug from one of the microswitch terminals. Slowly opening the throttle, increase the crankshaft speed over 1500 min -1 and fix this position. In this case, a self-oscillatory mode of operation of the engine should occur, accompanied by a pulsation of the rotational speed.

The emergence of a self-oscillatory mode is explained by the fact that when the rotation speed increases to 1500 min -1, the electrical connection of the terminals 1 and 2 of the block is broken (the solenoid valve power circuit is forcibly broken through the microswitch), which causes the fuel supply to the engine to be turned off. At the same time, the rotation frequency decreases and after it falls below 1245 min -1 (1140 min -1 for blocks 25.3761 or 2533.3761), the indicated connection is restored, i.e. the fuel supply is resumed and the engine speed is increased.

If it is not possible to cause the self-oscillatory mode, and the electromagnetic valve and the EPHX pneumatic valve do not have a defect, then the control unit is faulty and must be replaced.

You can check the control unit by directly monitoring the speed at which the unit is triggered by the tachometer.

Required for verification control lamp 12 V and wires with plug-in lugs.

Disconnect the gray wire plug (+12 V) from the microswitch in series, and the plug with the double pink wire from the solenoid valve output. On the released output of the solenoid valve, put on the plug disconnected from the microswitch, which will ensure the passage of current through the solenoid valve winding. With the plug removed from the solenoid valve, connect one output of the control lamp, connect the other output of the lamp to the "mass" of the car.

At idle (850 ± 50) min -1, the control lamp should be on. When the speed increases to 1500 min -1 ± 5%, the lamp should go out and light up again when the speed drops below 1245 min -1 ± 5% (1140 min -1 ± 5% for blocks 25.3761 or 2533.3761).

After checking, reinstall the removed plugs.

Design features

Microswitch type 421.3709 () acts on the solenoid valve in addition to the control unit.

In the initial position, the microswitch contacts are closed. With the throttle pedal fully released, the microswitch pusher is recessed and its contacts are open. When you press the pedal, the pusher of the microswitch is released, its contacts close, and the current passes through the solenoid valve winding, regardless of the control unit.

Checking the microswitch

The microswitch is checked on the car. In idle mode, remove the pink wire plug from the microswitch output, connect the freed output of the microswitch to one of the outputs of the control lamp, its second output to the car's ground. In this mode, the lamp should not light up.

Watching a control lamp, smoothly increase frequency of rotation of a cranked shaft, having opened a butterfly valve. The control lamp should light up until the self-oscillatory mode of engine operation occurs.

If the control lamp lights up already at idle (early adjustment of the microswitch operation) or lights up after the onset of self-oscillating mode (late adjustment), adjust the setting of the microswitch. To do this, loosen the two fixing screws of the microswitch and, after selecting its new position, tighten the fixing screws.

If the control lamp does not light up at any throttle position, then the microswitch is faulty.

After checking, reinstall the removed plug.

NOTES 1. Early adjustment of the microswitch operation reduces the efficiency of the EPHX to a complete loss of effect (when the microswitch contacts are closed with the accelerator pedal fully released). Late adjustment of the microswitch actuation causes the vehicle to jerk when driving on low speed especially when driving slowly in reverse. Therefore, try to set the microswitch to operate as late as possible, avoiding the occurrence of self-oscillating mode. The operation of the microswitch is judged by characteristic clicks. 2. A simplified adjustment of the position of the microswitch is allowed, in which achieve the operation of the microswitch within freewheel throttle drive mechanism of the first chamber of the carburetor.

Solenoid valve EPHH

Design features

Solenoid valve type 19.3741 or 1902.3741 () is used to control the EPHX pneumatic valve in the carburetor.

The solenoid valve has three fittings and two locking elements. The first locking element 7 is made normally closed and serves to separate the central fitting 6 (connected to the engine inlet pipeline) from the inclined fitting 5 (connected to the fitting of the EPHX pneumatic valve); the second locking element 4 is made normally open and serves to isolate the specified inclined fitting from the atmospheric fitting 1, closed by a felt filter and located between the electrical terminals 10 of the winding 9 of the valve.

When current passes through the winding of the solenoid valve, the central and inclined fittings are pneumatically connected, and in the absence of current, the inclined and atmospheric fittings are connected in this way. In the first case, the vacuum from the inlet pipeline is transferred to the EPHX pneumatic valve, which ensures the supply air-fuel mixture through the idle system to the engine, and in the second case, the EPHX pneumatic valve blocks its supply.

Checking the solenoid valve

The solenoid valve is checked on the car. At idle, remove the plug from one of the valve leads, as a result of which the engine should stop within 1–2 s. If this does not happen, then first make sure that the EPHX pneumatic valve is in good condition. If the EPHX pneumatic valve does not have a defect, then the solenoid valve is faulty and needs to be replaced.

After checking, do not forget to reinstall the removed plug.

When driving in a city, the engine runs about 25% of the time at forced idle, when the engine crankshaft rotates due to the kinetic energy of the car and it moves with the gear engaged and the throttle pedal released. In these modes, the engine is controlled by a forced idle economizer.

UAZ forced idle economizer control system, control unit, valve, microswitch.

At forced idle, the engine consumes fuel without performing useful work, as a result of the rapid closing of the throttle valve, the combustible mixture is re-enriched and the toxicity of the exhaust gases increases. To reduce fuel consumption and exhaust gas toxicity on UAZ vehicles, a electrical system forced idle economizer control (EPKhH).

The control system and electrical equipment of the forced idle economizer on UAZ vehicles with UMP engines includes control unit 1422.3733, solenoid valve 1902.3741 and carburettor limit switch (microswitch) 421.3709.

The principle of operation of the forced idle economizer control system on UAZ vehicles.

The forced idle mode is characterized by two signs: the engine speed is greater than the idle speed and the carburetor throttle is closed. Information about the engine crankshaft speed is supplied to the EPHX control unit from a sensor, which is used as the primary winding of the ignition coil, and information about closing the throttle valve is from a limit switch, microswitch or screw sensor.

When the accelerator pedal is released, as a result of switching the contacts of the carburetor limit switch, the EPHX control unit generates control signals for the electromagnetic (electro-pneumatic) fuel supply valve, depending on the engine crankshaft speed. If the crankshaft speed is higher than the idle speed, then the control unit removes voltage from the solenoid valve and the fuel supply to the engine stops.

At the same time, the crankshaft speed decreases, and when it becomes less than the idle speed, the control unit will turn on the voltage onboard network to the solenoid valve. The fuel supply will resume and the engine speed will increase.

When the crankshaft speed is again greater than the idle speed, the control unit will again turn off the solenoid valve. The process is repeated. Periodic shutdown of the fuel supply in this mode reduces gasoline consumption by 2-3%, and the toxicity of exhaust gases decreases by 15-30%.

When you press the accelerator pedal, the contacts of the limit switch switch in such a way that the voltage of the on-board network is constantly supplied to the solenoid valve. In this case, fuel will be supplied regardless of the engine speed.

Control unit 1422.3733 of forced idle economizer on UAZ vehicles, principle of operation.

On UAZ vehicles with UMZ engines, four-pin economizer control units 1422.3733 are used. Microswitch 421.3709 is used as throttle position sensor. When the throttle is closed, voltage pulses proportional to the speed of the crankshaft come from the primary winding of the ignition coil 1 to the input of a semiconductor key assembled on a transistor VT1.

During the action of the pulse, the key opens and the capacitor C3 is discharged. In the pauses between pulses, the capacitor C3 is charged. The charge time, and hence the voltage on the SZ, increases with a decrease in the crankshaft speed. At a frequency greater than the idle frequency, the voltage on the SZ is small, the transistors VT2, VT4, VT5, VT6 close. The solenoid (electro-pneumatic) valve is not energized.

The valve closes and the fuel supply stops. The crankshaft speed drops. At a frequency less than the idle frequency, the capacitor C3, during the pause between pulses, has time to charge up to a voltage exceeding reference voltage threshold element assembled on transistors VT2, VT4. Transistors VT2 and VT4 open at the same time, which ensures the opening of transistors VT5 and VT6. At the same time, voltage is applied to the electropneumatic valve.

The valve activates and turns on the fuel supply. When the throttle is opened, the contacts of the microswitch S1 are closed and the voltage of the on-board network is constantly supplied to the electro-pneumatic valve. The valve is constantly open, regardless of the signals of the control unit 1422.3733 of the forced idle economizer.

Despite the massive exclusion carburetor systems injection, a huge number of engines of the old design are still on the go. Many classic VAZ models are equipped with Solex or DAAZ carburetors. To adjust the power of the motor, depending on the load, so-called economizers are installed. These devices work by analogy with electronic control units. injection motors. Of course, it will not be possible to achieve the same parameters of efficiency and environmental friendliness of the engine, but the quality of work carburetor engine improves significantly.

In fact, any economizer is a valve that is actuated by an electromagnet or a piezoelectric element. It is controlled by a simple programmable computer (more like a controller), and allows you to adjust the basic settings. The purpose of the economizer comes from the name: to increase efficiency power unit without loss of power taken from the crankshaft.

Note that it is impossible to install an economizer on a carburetor that is not designed for this. The design of the chambers is specially calculated for operation with controlled valves.

The economizer system also needs periodic maintenance, like the rest of the valves and carburetor jets. To understand the mechanism of work, we will analyze the popular carburetors installed on the classics and front wheel drive models VAZ.

Carburetor economizer device

The node is made as a separate module in its own housing. The actuator is inside and is not serviceable. From the outside, the electrical part with the contacts of the connection connector, from the inside (located in the cavity of the carburetor chambers) the valve head. If the economizer has mechanical drive, there are no connection wires.

It serves to control the supply of fuel. The control module receives data from various sensors (the system works almost like an injector), and, based on the installed factory program, gives the command executive mechanisms. Accordingly, the mechanical unit operates when the drive actuation conditions are created. The following types of devices are installed on most carburetors:

Forced idle economizer (abbreviation: EPHH)

The device is designed as technical development idle valve. It also has some unique features. The valve can completely block the flow of fuel through the idle jet. The control controller receives two signals: a certain number of revolutions of the crankshaft, and the absence of movement of the accelerator pedal. The system allows significant fuel savings during engine braking. The compression of the cylinders dampens the crankshaft speed, while gasoline does not enter the combustion chambers. Accordingly, there is no negative effect when unburned fuel enters the muffler and burns in it. In the past, drivers switched to neutral gear, to save on long descents. This is unsafe, besides, the brakes in the car overheat and wear out. In gear mode, the handling of the car is more predictable, and there is always the possibility of braking with cold pads, which cannot be done when coasting.

When communicating with professional service masters, you can hear the abbreviation EMC (solenoid valve). This is a slang term for EPPH.

The photo shows how the EPPH is located and how to dismantle it.

Economizer of power modes (EMR).

Technically done as vacuum regulator. Works in mechanical mode, which makes it reliable and unpretentious in maintenance. The economizer diaphragm provides a normally open valve (based on the principle of electromagnetic relays). Only instead of a coil and a core, a ball and a spring are used.

The location and components of the EMR can be seen in the illustration:

An open ball valve freely passes gasoline through the jet channel. At moderate loads, a natural vacuum occurs in the carburetor chamber, setting the economizer membrane (diaphragm) in motion. This force is greater than the resistance of the ball spring. The additional flow of gasoline stops, fuel economy occurs. With a stronger pressure on the accelerator, the vacuum decreases, the membrane goes into rest mode. The system reopens an additional flow of gasoline, providing additional power pickup due to the forced enrichment of the mixture.

Economizer malfunctions

Like any other unit, the economizer is subject to wear and tear. Signs by which you can determine its malfunction:

• Regardless of the heating of the engine, there are interruptions at idle;
• A warm engine does not start well;
• unjustifiably high flow gasoline;
• A double sign - and the consumption has increased, and the power has fallen. This is especially noticeable when driving in mountainous areas;
• The power mode economizer “sweats” with gasoline (typical for a Solex carburetor)

Any of these signs indicates a malfunction of one of the economizers, but only on condition that the rest of the engine systems are working.

Unfortunately, economizers cannot be repaired; you will have to buy a new one to replace them. Some manufacturers produce spare valves, for example, for the Solex carburetor, but DAAZ offers to purchase a whole carburetor. However, given the huge number of engines produced, finding a used carburetor with a working economizer is not difficult.

Do not immediately run for a new (or serviceable used) spare part. In most cases, a little adjustment, or even just cleaning the moving parts of the device, helps. You need to regularly inspect and analyze the work of economizers, then you will not encounter a sudden breakdown.

Having figured out how the economizer works, you can easily restore the problem node if there is no breakdown inside the case.

Replacement and preventive maintenance

The positive idle economizer of the carburetor has electric drive, therefore, if it fails, first of all we look at the wiring and the condition of the contacts. Then carefully dismantle the device using an open-end wrench.

It is not necessary to remove the carburetor itself, it is enough to drain the chamber from fuel.

Important! Similar works associated with the risk of fire from gasoline!

Therefore, no cigarettes during operation, and a serviceable fire extinguisher must be available in the area.

Having unscrewed the EPPH, we wash it with a carb cleaner, and check its performance with a battery. A serviceable valve should operate 5 mm. If not, we try to flush the place where the rod enters the sleeve. It did not help - we put a new device.

For prevention, it does not hurt to flush the economizer jet hole located in the carburetor. After flushing, all nodes are blown with compressed air.

It is useless to repair the power mode economizer, it must be changed immediately. The actual repair consists in replacing the membrane and springs, which are the main components. The lid doesn't break. It comes off with a screwdriver.

If you have any questions - leave them in the comments below the article. We or our visitors will be happy to answer them.

The efficiency of the engine and the level of toxicity of exhaust gases are provided electronic system EPHH control. This system shuts off fuel to the engine during over idle modes when the throttle pedal is released and the engine, while still connected to the transmission, has an increased engine speed compared to idle. This causes engine braking. In the absence of the EPHH system, the engine in this operating mode continues to consume fuel, and its consumption is proportional to the consumption in idle mode, taking into account the increased crankshaft speed.

When using the EPHX system on a car, after releasing the accelerator pedal, despite the increased engine speed, the fuel supply is turned off. When the fuel supply is turned off in the forced idle mode, combustion stops fuel mixture in the engine cylinders, and engine braking becomes more effective. This is especially important when driving on mountain roads, where engine braking is used most often.

positive quality The EPHH system is also an automatic shutdown of the fuel supply after the ignition is turned off, which eliminates uncontrolled engine operation during self-ignition of the fuel mixture in the engine cylinders, which occurs when operating vehicles not equipped with the EPHH system.

Principle of operation and device EPHH systems on both models of cars are identical and differ only in design individual elements. In particular, on the 2106 engine, a microswitch of type 421.3709 was used to determine the position of the carburetor throttle, and on the 331 engine, a sensor-screw. Shutting off the fuel supply on the 2106 engine is performed by the EPHH pneumatic valve, which is part of the carburetor. The pneumatic valve is controlled by an electromagnetic valve, which is affected by a control unit and a microswitch. Fuel is supplied to the engine cylinders only when there is voltage on the solenoid valve.

Solenoid valve on the engine 331. built directly into the carburetor and made normally closed: when the winding is de-energized, the valve needle shuts off the fuel supply, while when current flows through the valve winding, its locking element1 does not prevent the fuel supply.

The solenoid valve is controlled by a microswitch or screw sensor, which are installed on the carburetor and work depending on the throttle position, as well as using an electronic control unit. A microswitch or screw sensor supplies voltage to the solenoid valve winding after pressing the accelerator pedal, that is, when the carburetor throttle is opened. The voltage supply to the valve winding by the control unit occurs after the frequency of rotation of the crankshaft, the engine, falls below a certain value.

Thus, fuel is supplied to the carburetor idle system either when the engine is running, idling with low. rotational speed of the crankshaft - due to the supply of voltage to the solenoid valve winding by the EPHX control unit, or when the accelerator is pressed by means of a microswitch or sensor ^ of the screw - when the car is accelerating. When the car is moving in engine braking mode, i.e., with the accelerator pedal released, and the crankshaft rotates at a frequency of more than 1500 rpm for an engine of 2106 and 2100 rpm for 331 (the threshold for the operation of the EPHX control unit), there is no voltage at the solenoid valve terminals and no fuel is supplied to the carburetor idle system. The fuel supply is resumed when the engine speed drops to 1140 rpm on the 2106 engine and 1900 rpm on the 331 engine (due to the action of the EPHX control unit) or after pressing the accelerator pedal (due to the action of the microswitch or screw sensor).

EPHH control unit

Device and work. To control the solenoid valve according to the signals of the ignition system (depending on the frequency of rotation of the engine crankshaft) and the throttle position screw sensor (depending on the engine load) on the engine 331.10, an electronic control unit 50.3761 is used. The control of the engine speed is carried out by the EPHX control unit by measuring the repetition frequency of the ignition system pulses, which are taken from the ignition coil and fed to the output "1" of the control unit. At the same time, a signal is sent from the sensor-screw to the control unit, which makes it possible to distinguish between the open and fully closed position of the carburetor throttle. Conclusions "4" and "6" EPHH block, which ensure the flow of current through the winding of the electromagnetic valve, have an electrical connection regardless of the signal of the sensor-screw at an engine crankshaft speed of less than 1900 rpm. At the same time, with open throttle

when the movable and fixed contacts of the sensor-screw are open, the conclusions "4" and "6" of the control unit are electrically connected, regardless of the frequency of rotation of the engine crankshaft.

After closing the contacts of the sensor-screw when the accelerator is released with a crankshaft speed of more than 2100 rpm (in the engine braking mode), the electrical connection of the outputs "4" and "6" of the control unit is broken, the solenoid valve is de-energized It stops and the fuel supply to the carburetor idle system stops. The resumption of the fuel supply occurs when the electrical connection between the outputs "4" and "6" of the control unit is restored, either after the engine crankshaft speed is reduced to 1900 rpm, or - after opening the sensor contacts - screws when pressing the accelerator.

Possible malfunctions of the control unit, their causes and remedies are given in Table. 11.19.

If the solenoid valve is in good condition, and the crankshaft speed does not decrease, then the EPHX control unit needs to be replaced.

Checking the block can also be carried out by directly monitoring the speed of the engine crankshaft, at which the block is triggered, according to the readings of the control tachometer. To do this, disconnect the plug tip of the wire that is not connected to the mass of the car from the output of the solenoid valve and connect it to one of the outputs of a low-power (1-3 W) control lamp (12 V), the second output of which is connected to vehicle weight. To ensure the operability of the solenoid valve, connect its released output with the help of an auxiliary wire to the positive pole of the car's onboard network.

With the engine idling, remove the plug from the screw sensor. The control lamp should be on. Gradually opening the throttle valve of the carburetor, increase the engine speed of the crankshaft to about 2100 rpm. Connect the plug tip of the wire removed from the output of the sensor-screw to the mass of the car. The control lamp must then go out. Then, smoothly closing the throttle valve, reduce the engine crankshaft speed. At the moment the control lamp lights up, measure the tachometer readings, which should be within 1900 rpm ± 5%.

Carburetor Throttle Position Screw Sensor

On the 331 engine, a screw sensor is installed on the carburetor to register the fully closed position of the throttle valve. The output of the sensor-screw, connected to a fixed contact with a fully closed throttle, is connected to the mass of the car, and for all other positions of the throttle, it does not have such a connection.

To check the operability of the screw sensor on a car, you need to remove the plug tip from its output connecting wire and connect the released output to one of the outputs of the control lamp, the second output of which is connected to the positive pole of the car's on-board network (+ 12 V). When the throttle is fully closed, the control lamp should be on. If the lamp does not light up, then it is necessary to turn the sensor-screw clockwise until the control lamp lights up, and then check the crankshaft speed using the tachometer, the readings of which should be within (850 + 50) rpm . When opening the throttle valve, the control lamp should go out. If this does not happen, then the screw sensor is faulty ( short circuit not under-

(visible contact to ground) and needs to be replaced.

In table. 11.20 shows possible malfunctions of the screw sensor, their causes and remedies.