Sensor-distributor ignition 3810.3706: 1 - roller; 2 – the case of the gauge-distributor of ignition; 3 - latch; 4 – contactless sensor; 5 - housing of the vacuum regulator; 6 - diaphragm; 7 – draft of the vacuum regulator; 8 - base plate of the centrifugal regulator; 9 – ignition distributor rotor; 10 – side electrode; 11 - cover; 12 – central electrode; 13 - coal of the central electrode; 14 - resistor; 15 - outer contact of the rotor; 16 - leading plate of the centrifugal regulator; 17 – centrifugal regulator weight; 18 – contactless sensor support plate; 19 - screen.
Scheme for checking a proximity sensor on a car: 1 - sensor-distributor ignition; 2 - voltmeter with a scale limit of at least 15 V and an internal resistance of at least 100 kOhm; 3 - view of the plug connector of the ignition distributor.
Scheme of a contactless ignition system: 1 - ignition switch; 2 - ignition relay; 3 - switch; 4 - ignition coil; 5 - sensor-distributor ignition; 6 - spark plugs.
The ignition system is non-contact. It consists of a distributor sensor, a switch, an ignition coil, spark plugs, an ignition switch and high and low voltage wires. A small part of cars with a 1600 cc engine3 equipped with a microprocessor-based engine control system, which is not described here.
Ignition distributor 3810.3706 - four-spark, with a non-contact sensor of control pulses and built-in vacuum and centrifugal ignition timing controllers. Initial ignition timing at crankshaft speed 750–800 min–1 should be 1±1°before TDC.
The distribution sensor performs two main functions: firstly, it sets the moment of sparking depending on its initial setting, the number of revolutions of the crankshaft and the engine load, and secondly, it distributes high voltage pulses («spark») on the cylinders in accordance with the order of their work - for this the rotor is used (slider). In order not to be mistaken during assembly, the slider is installed on the base plate of the centrifugal regulator in only one position. The slider has a noise suppression resistor with a resistance of 1 kOhm.
The operation of the proximity sensor is based on the Hall effect. When the ignition is on, the sensor is supplied with voltage. When the roller of the sensor-distributor rotates, a steel screen with rectangular cutouts passes through the gap of the sensor. While the screen plate is in the gap, voltage is removed from the control output of the sensor, as soon as there is a cutout in the gap, the voltage at the control output drops sharply. Thus, the non-contact sensor for each revolution of the sensor-distributor roller produces four rectangular pulses (by the number of notches in the screen), which corresponds to the moment of ignition in each of the engine cylinders.
You can check the performance of the proximity sensor by assembling the circuit shown in the figure. Slowly rotating the ignition distributor roller, we monitor the readings of the voltmeter. The voltage should change sharply from the minimum (no more than 0.4 V) up to maximum (no more than 3 V less than the supply voltage). A faulty sensor cannot be repaired (except for a break in the wires between the sensor itself and the block on the housing of the sensor-distributor). If the slotted steel shield touches the sensor (is determined by a slight jamming or scratching sound during the rotation of the roller, as well as visually, after partial disassembly of the distribution sensor), check the end play of the roller and the fit of the screen. If necessary, replace the distribution sensor.
The centrifugal regulator increases the ignition timing with an increase in the engine speed, entering into operation at 900–1400 min–1. When the roller of the sensor-distributor rotates, the weights of the regulator under the action of centrifugal forces diverge, overcoming the resistance of the springs, and shift the base plate of the centrifugal regulator clockwise relative to the roller. For optimal operation of the regulator, the springs have different stiffness. More rigid (thick) the spring comes into operation later, approximately in the middle of the full stroke of the plate - therefore it is put on the rack with a gap, while the softer one (thin) the spring is always under tension. The maximum movement of the base plate is limited by a cutout in it and is about 12°along the distributor, which corresponds to an ignition timing angle of about 24°along the crankshaft.
When inspecting the centrifugal governor, make sure that the weights move freely on the axles, their damper plastic rings are not lost, the thin spring is tensioned, and the base plate returns to its original position under the action of the springs. If necessary, lubricate the distributor shaft with a few drops of engine oil.
The vacuum regulator increases the ignition timing depending on the load on the engine. It consists of a vacuum chamber with a steel spring-loaded diaphragm, which is connected by a rod to the base plate of the proximity sensor. Under the action of vacuum, the membrane flexes, overcoming the resistance of the spring, and rotates the base plate counterclockwise. Maximum travel is limited by a cutout on the rod and is about 9°across the valve (18°crankshaft).
The vacuum for the operation of the vacuum regulator is taken from the hole in the mixing chamber of the carburetor opposite the throttle valve of the first chamber. When the damper is partially opened (partial load) the vacuum behind it is large, and the regulator maximally shifts the moment of sparking in the direction of advance. When the damper is fully open (full load) the vacuum behind it drops, and the regulator returns the base plate of the contactless sensor to its original position.
You can roughly assess the health of the vacuum regulator directly on the car. With the engine running, disconnect the vacuum hose leading to the regulator from the carburetor fitting. If we now create a vacuum in the hose (you can mouth), the engine speed should increase, and when the vacuum is removed, it should decrease again. The vacuum must be maintained for at least a few seconds if the hose is pinched. Visually, the performance of the vacuum regulator can be verified by partially disassembling the distribution sensor (see Dismantling of the gauge distributor of ignition) and applying vacuum to the inlet fitting of the regulator. In this case, the screen of the distribution sensor should rotate by an angle of 9±1°, and when the vacuum is removed, it should return without jamming.
An accurate check and adjustment of the vacuum and centrifugal ignition timing controllers is carried out on special stands. It is not recommended to do this at home. If the vacuum regulator fails, it should be replaced, if the centrifugal regulator fails, the distribution sensor should be replaced.
The switch - type 3620.3734, or HIM-52, or BAT10.2, or 76.3734, or RT1903, or PZE4022 - opens the power circuit of the primary winding of the ignition coil, converting the control pulses of the sensor into current pulses in the ignition coil. The switch is checked by an oscilloscope using a special method and is not repairable; if a malfunction is suspected, it is recommended to replace it. Do not disconnect the switch connector when the ignition is on - this may damage it (as well as other components of the ignition system).
Ignition coil - type 27.3705 or 27.3705-01, or 8352.12, or ATE1721 - oil-filled, with an open magnetic circuit. Test data: Primary winding resistance at 25°C - (0,45±0,05) Ohm, secondary winding - (5,0±0,5) kOhm Insulation resistance to ground - not less than 50 MΩ.
Spark plugs - type A17DVR or A17DVRM, or A17DVRM1, or their imported analogues (with interference suppression resistors 4–10 kOhm). The gap between the electrodes is 0.7–0.8 mm.
High voltage wires - with distributed resistance (2550±270) ohm/m Do not touch high-voltage wires while the engine is running, as this may result in electrical injury. It is also forbidden to start the engine or allow it to run with an open high voltage circuit (removed wires or cover of the sensor-distributor) - this can lead to burnout of the insulation and failure of the electronic components of the ignition system. As an exception, a short-term check of the ignition system is allowed «for a spark», while the contact of the high-voltage wire under test must be securely fixed at a distance of 8–10 mm from «masses» car. Do not hold the wire with your hands or with a tool (even with insulated handles).
Ignition switch - type 2101-3704000-11, with anti-theft locking device. When the key is turned to position «ignition» voltage is supplied to the control input of an additional relay, which, in turn, supplies voltage to the ignition coil and switch.