Checking the Throttle Position Control
Disconnect the throttle position control plug.
Apply a maximum voltage of 6 V to the connecting contacts of the potentiometer; positive pole on top.
For a 4-pole plug, these are pins 1 and 2.
On a 6-pole plug, these are pins 1 and 6.
The desired voltage can be obtained from a 4.5-volt battery or a 6-volt charger range.
On the block of preparation of a combustible mixture, in the direction in the direction of the vehicle, there is a throttle position regulator (1) with connector (2).
The pusher must fully retract.
Change the pole of the connecting wire (negative contact at the top contact pin).
The pusher must be fully extended.
If everything happens as described, then the throttle position control is in order. If not, it must be replaced.
Additionally, you can take resistance measurements.
The resistance of the winding of the auxiliary motor between the already mentioned connections is 3-200 ohms.
Check of operation of the switch of a signal of idling
Disconnect the plug from the throttle position control.
Connect an ohmmeter to the contacts of the idle signal switch.
On a 4-pole plug, these are pins 3 and 4 (both lower).
On a 6-pole plug, these are pins 4 and 5 (look down).
If the idle switch is pressed: 0 ohm resistance.
If the idle switch is not pressed: the resistance is infinite.
Note: after replacing the throttle control, the idle signal switch must be adjusted - this is a job for the workshop.
Throttle Potentiometer Check
Disconnect the plug of the throttle valve potentiometer.
Connect an ohmmeter according to the table (shown on the next page) to two of the four plug contacts.
If the specified values are not achieved, then the throttle valve potentiometer is faulty. Unfortunately, you can't just replace it. The entire lower part of the block for preparing a combustible mixture always changes.
Checking the injection nozzle
Check with the engine running: the oil temperature must be at least 60°C, which corresponds to 10 minutes of driving after starting a cold engine.
Remove the air intake pipe.
Start the engine and let it run at idle.
Monitor the flow of injected fuel. It should be uniform and directed towards the throttle valve.
Stop the engine to check the tightness of the valve.
With the engine off, no more than two drops per minute should come out.
You will need to carry out further checks if the engine does not start.
Check fuses 14, 17 and 19 as well as the fuse in the red holder in the electronics box (Chapter «Body electrical system»).
Remove the air filter and air intake pipe.
Turn the engine over with the starter.
The injection nozzle should visibly inject fuel.
If not, disconnect the brown plug at the top of the fuel mix unit.
Connect an ohmmeter to both middle connecting pins (on the combustible mixture preparation unit).
At an ambient temperature between +15°and +30°C, the ohmmeter should show 1.2-1.6 ohms, otherwise the injector is faulty. Loosen the star head screw and replace the injector.
Check the power supply to the injection nozzle if it does not work despite the correct resistance readings.
Connect the LED voltmeter, without using another device, to both middle contacts in the removed plug.
Turn on the starter: the LEDs should flicker, otherwise there is a wire break or a malfunction of the control unit.
Remove the air filter or air intake pipe.
Forced Idle Fuel Cut Check
Start the engine, quickly bring the speed to 3000 rpm, and then sharply close the throttle.
The clearly visible injection jet of the injection nozzle must stop briefly at this point. In this case, overrun fuel cutoff is OK.
If not, check throttle angle sensor and control unit (In workshop).
Checking temperature sensors
Intake air temperature sensor: Disconnect the brown plug at the top of the combustion unit.
Connect an ohmmeter to both external plug contacts.
Coolant temperature sensor: unplug connector at sensor (blue) in the coolant filler pipe.
Connect an ohmmeter to the sensor contacts.
Both sensors: read resistance readings.
Using the diagram on the next page, you can check whether the resistance readings of the sensors, as well as the air and coolant temperatures at the time of measurement, are within the allowable range.
If so, then the sensors are OK.
Fuel pressure test
The fuel supply pressure can only be precisely controlled by a measuring device used in the workshop.
If you suspect an incorrect fuel supply pressure, disassemble the pressure regulator: unscrew the 4 star head bolts.
Check if the diaphragm is damaged or if there are any fouling deposits.
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