Fuel injection system

Adjusting the mixture composition of the Bosch L-Jetronic fuel injection device

ONS 2.0 dm³ NRB engines are equipped with Bosch L-Jetronic multipoint fuel injection system. It provides a constant injection pressure, while the fuel dose is regulated by the opening time of the electronically controlled injectors. During engine braking, fuel metering is automatically switched off.

Removing and installing throttle contactor

1. Disconnect ground wire from battery.

2. Disconnect the throttle contactor electrical connector, being careful not to damage the spring clip.

3. Remove the throttle contactor.

4. When installing, correctly position the contactor relative to the flat part of the throttle shaft.

5. Install washers and contactor mounting bolts, tighten them.

6. Connect the throttle contactor electrical connector and ground wire to the battery.

Idle adjustment

1. Warm up the engine to normal operating temperature.

2. Connect tachometer and exhaust gas analyzer.

3. Bring the engine speed to 3000 rpm, hold it for 15 seconds and release the accelerator pedal, leaving the engine idling.


4. After stabilization of the instrument readings, read the idle speed and the CO content in the exhaust gases.

5. If necessary, adjust the CO content by turning the idle mixture adjustment bolt (see fig. Adjusting the mixture composition of the Bosch L-Jetronic fuel injection device) after removing the seal from the flowmeter.

6. Install a seal on the idle mixture adjustment bolt.

Attention! The idle speed is controlled by the EEC IV electronic control unit and a stepper motor that changes the throttle position accordingly. The idle speed cannot be adjusted manually.

Fuel pump

Vane roller pump driven by an electric motor. Brand: Bosch.

Compression pressure: above 500 kPa at 12 V and closed fuel outlet.

Fuel pressure control

Brand: Bosch. Regulated pressure: 250 kPa.

Working nozzles

The nozzles are electrically controlled. Brand and type: Bosch 85 TF-9 F 593-AB.

Adjustment data

Number of turns of idling: 850 rpm.

CO content: 0.5–1.0%