Table of contents: The principle of operation of the… ↓ Air filter ↓ Fuel electric pump ↓ Fuel storage tank ↓ Fuel filter ↓ Fuel dispenser ↓ Injection nozzles ↓ Starting nozzle ↓ Air flow meter ↓ Thermal time relay ↓ Idle speed control valve ↓ Data for adjustment ↓
The YZ and 0Z engines are equipped with the K-Jetronic mechanical continuous fuel injection system from Bosch.
The principle of operation of the fuel injection system
The fuel pump takes fuel from the fuel tank and delivers it to the accumulator, in which the fuel is under pressure of 1.5-2.4 kg/cm² when the engine is stopped. Then the fuel is delivered under pressure through the filter to the fuel dispenser-distributor.
The pressure disk of the air flow meter, which is fixed on the movable lever and installed between the air filter and the throttle valve, deflects depending on the vacuum of the air in the engine. The displacement of the pressure disk of the air flow meter is transmitted to the distribution plunger of the fuel metering unit, thereby determining the amount of fuel supplied. The fuel quantity distributor, depending on the position of the pressure disk of the air flow meter, supplies the required amount of fuel to the engine cylinders through the injectors, ensuring the optimal composition of the fuel-air mixture. The fuel metering unit and the air flow meter form a mixture regulator.
The control pressure regulator reduces the pressure on the distribution plunger during engine warm-up. Reducing the control pressure with the same air flow leads to an increase in fuel supply and, consequently, to enrichment of the combustible mixture.
The additional air supply valve, installed in the air channel parallel to the throttle valve, supplies an additional amount of air to the engine during cold starting and warming up of the engine, which leads to an increase in the engine crankshaft speed at idle.
To facilitate starting a cold engine, an electromagnetic starting injector is provided, the opening duration of which changes depending on the temperature of the coolant by a thermal time relay.
Air filter
Air filter with replaceable dry filter element.
Fuel electric pump
The fuel electric pump is placed in the fuel tank in a submerged position.
Fuel supply in 30 sec at terminal voltage of 12 V, cm³:
- pump with pin connector: 750;
- pump with threaded joint connector: 900.
Productivity at terminal voltage of 12 V, l/min 1.8.
Current consumption at terminal voltage of 12 V, no more than, A; 6.5.
Fuel storage tank
The fuel storage tank is installed under the body bottom next to the fuel tank on the right.
Fuel filter
The fuel filter is located in the engine compartment.
Control pressure regulator
Brand and catalog number: Bosch 0 438 140 073.
Resistance of the heating winding of the bimetallic spring of the regulator, Ohm:
- engine YZ: 16-22;
- engine DZ: 20-26.
Fuel dispenser
Brand and catalog number: Bosch 0 438 100 082.
Injection nozzles
Brand and catalog number: Bosch 0 437 502 015.
Volume of injected fuel, ml:
- at idle: 3.0;
- at full load: 8.0.
Injection start pressure, kg/cm²: 2.5-3.5
Maximum permissible difference in injection start pressure between injection nozzles, kg/cm²: 0.6.
Starting nozzle
Fuel injection duration, s
- at +35°C: 0;
- at 0°C: 6.
Air flow meter
Brand and catalog number: Bosch 0 438 120 128.
Thermal time relay
Brand and catalog number: Bosch 0 280 130 228.
Idle speed control valve
The fuel injection system of the DZ engine includes an idle speed control valve, which is controlled by a special electronic unit
The valve turns on at a crankshaft speed of 700 rpm and turns off at 1050 rpm.
Data for adjustment
Crankshaft speed at idle, rpm:
- yZ engine with contact ignition system or with contactless ignition system and digital idle speed stabilizer: 900-1000;
- yZ engine with contactless ignition system and digital stabilizer: 750-850;
- dZ engine: 850-950.
Carbon monoxide (CO) content in exhaust gases at idle, %:
- yZ engine: 1.0-2.0;
- dZ engine: 0.5-1.5.
Fuel pressure in the system, kg/cm²:
- yZ engine: 4.5-5.2;
- dZ engine: 4.7-5.4.
Control pressure on a warm engine, kg/cm²: 3.4-3.8.
Control pressure on a cold engine at an ambient temperature of 20°C:
- yZ engine (with the block disconnected from the control pressure regulator): 1,35-1,65;
- dZ engine (with the pads disconnected from the control pressure regulator and the additional air valve): 1,0-1,4.
Residual fuel pressure in the system, kg/cm²:
- 10 min after engine stop: 1.8;
- 20 minutes after engine stop: 1.6.
(The text is based on materials from the website «AudiManual»)