Features of troubleshooting in a digital ignition system (VAZ-2109)

Accurate diagnostics of digital ignition system components is possible only at service stations equipped with appropriate stands and devices: However, with the appropriate skills, an experienced car enthusiast can find the fault location using the recommendations below. In this case, it is necessary to observe the same precautions as for a contactless ignition system.

If the engine does not start or runs intermittently, it is recommended to start checking the ignition system from the high-voltage part in the following order.

Checking the high voltage part

To check, you will need a simple spark gap (figure 118) with two pairs of metal rods 2 and 5 (electrodes), fixed to a plate made of electrically insulating material (plastic, textolite). The lower part of the rods together with the insulators 7 must correspond in shape and size to the size of the insulator and the tip of the spark plugs. Screws 6 with pointed ends are screwed into the upper part of the rods. The gap between the ends of the screws can be adjusted by turning the screws.






When checking the high-voltage part, care must be taken. For this purpose, the arrester must be covered from above with a cover 3 made of insulating material with viewing windows 4. The arrester must be fixed to the car body.

Disconnect the wire tips from the spark plugs and connect them to the spark gap electrodes. Connect the wires from the spark plugs of the 1st and 4th cylinders to one pair of electrodes, and from the spark plugs of the 2nd and 3rd to another pair of electrodes. Set the gap between the spark gap electrodes to 7...10 mm and turn the engine with the starter.

At low crankshaft speed, alternate spark jumps between pairs of electrodes 2 and 5 will be noticeable. If spark formation on the spark gap is normal, then it is necessary to check all spark plugs.

If there is no sparking on one pair of electrodes, then it is necessary to check the electrical circuit from the commutator to these electrodes: high-voltage wires, interference suppression tips, ignition coil and the connection of the coil to the commutator.

When there is no sparking on both banks of the spark gap electrodes, it is necessary to check whether power is supplied to the switch, controller and ignition coils, and also to check the switch, controller and NO and UI sensors if the power supply circuits are in good condition.

Switch

The simplest test of the switch can be performed using the A12, 3 W lamp. To do this, disconnect the low-voltage wires from the ignition coil, connect the lamp to them and turn the engine with the starter. The flashing of the lamp will indicate that the switch is producing current pulses.


If there are no current pulses on only one ignition coil, then either the wires connecting this ignition coil to the switch are damaged, or one of the switch channels is faulty.

If there are no current pulses on both coils, then either the supply voltage is not supplied to the ignition coils, the switch or the controller (via the blue wire with the red stripe), or the fault must be looked for further. Perhaps it is in the switch, controller or in the connections between them.

If you have a known good switch, you can replace the car switch with it and check the operation of the ignition system. Its normal operation in this case will indicate that the car had a faulty switch.

Controller

The simplest check of the controller's performance can be performed using an indicator assembled according to the circuit in Figure 119. The indicator uses resistors of the MLT type, 1 W, a transistor of the KT817B type, and an A12, 3 W automobile lamp as the indicator lamp L1.



To check the controller, it is necessary to connect the terminals "-" and "+" of the indicator to the battery, disconnect the block of the plug connector from the switch and connect the input "A" of the indicator to the plug "5" of this block (connected to the white wire). Turn the engine with the starter. If the indicator lamp flashes, the controller issues a "Channel Selection" pulse.

The presence of "Ignition signal" pulses is checked in a similar manner by connecting the indicator input to plug "6" (there is a blue wire coming to it) wiring harness disconnected from the switch.

If there are no pulses, then you should check whether the supply voltage is supplied to the controller and whether there is a break in the wires connecting the controller to the switch and to the NO and UI sensors. If the wires are intact and the supply voltage is supplied to the controller, but there are no pulses, then you need to check the controller on the stand at the service station.

To check the carburetor solenoid valve control function, disconnect the green wire from limit switch 8 (see figure 112) carburetor and connect the tip of this wire to the "ground". Then start the engine and gradually increase the crankshaft speed. At 1750 rpm (measured by some additional tachometer) the valve should turn off. Now smoothly reduce the rotation speed. When it decreases to 1650 rpm, the valve should turn on.

Set the rotation speed to 2000 rpm, disconnect the tip of the wire going to the carburetor limit switch from the ground, and then reconnect it to the ground. When disconnecting the wire from the ground, the valve should turn on, and when connected to the ground, it should turn off. The moment of valve operation can be determined by a characteristic click or by using a voltmeter connected to the valve and the ground. If the valve is on, the voltmeter should show a voltage of at least 10 V, and if off, no more than 1.5 V.

The original can be seen on the website: VAZbook.ru

Ignition coil

The ignition coil is checked to see if there is a break in the winding or a short circuit between the windings, as well as if there is a breakdown of the insulation to ground, which is detected by burnout or melting of the plastic shell of the coil on its side adjacent to the mounting bracket.

Synchronization sensors

The presence of pulses generated by the sensor can be roughly estimated using an AC voltmeter by turning the engine with the starter. If there are no pulses, then it is necessary to check whether there is a break in the sensor winding and whether the sensor is installed correctly. For normal operation of the sensor, it is necessary that the gap between the sensor and the top of the flywheel crown tooth (or the end of the pin for the NO sensor) was within the range of 0.3...1.2 mm (figure 120).

Temperature sensor

To check, place the sensor in a tank with water and connect a power source and a voltmeter to it (figure 121). After turning on the water heating, measure the voltage drop on the sensor at different temperatures in the tank. The voltage drop should not differ by more than ±0.1 V from the calculated value, determined by the formula: U = 10 TK [mV].

Here TK is the temperature of the water in the tank, expressed in K.