K-Jetronic fuel injection system
The engines of the 230 and 280 models were equipped with a mechanical fuel injection system "K-Jetronic" bosch company.
The principle of operation of the fuel injection system
The fuel pump takes fuel from the fuel tank and delivers it to the accumulator, where the fuel pressure in the system is maintained within 4.5-5.2 kg/cm². The fuel is delivered under pressure through the filter to the fuel dispenser-distributor.
The air flow meter pressure disk, which is mounted on a 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 air flow meter pressure disk is transmitted to the distribution plunger of the fuel dispenser-distributor, thereby determining the amount of fuel supplied. The fuel quantity distributor, depending on the position of the air flow meter pressure disk, continuously supplies the required amount of fuel to the engine cylinders through the injectors, ensuring the optimal composition of the fuel-air mixture. The fuel dispenser-distributor 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 starting and warming up the engine, which leads to an increase in the engine crankshaft speed at idle.
To facilitate starting a cold engine, an electromagnetic starting nozzle is provided, the opening duration of which is regulated depending on the temperature of the coolant by a thermal time relay.
Data for adjustment
Characteristic | Meaning |
| Fuel pressure in the system, kg/cm² | 4,5—5,2 |
| Control pressure on warm engine, kg/cm² | 2,7—3,1 |
Control pressure when the engine is warmed up and idling, kg/cm² | 3,4—3,8 |
| Control pressure on a cold engine depending on the coolant temperature (see Checking the injection system), kg/cm² | 0,5—2,0 |
| Residual fuel pressure in the system, not less than, kg/cm² | 1,7 |
| Crankshaft speed at idle, rpm | 900±50 |
Carbon monoxide (CO) content in exhaust gases, % | |
| 1,1 |
| < 3,0 |
Fuel pump
Electric multi-section fuel pump.
Characteristic | Meaning |
| Brand and catalog number | Bosch 0 580 254 982 |
| Fuel supply pressure, kg/cm² | 5,5 |
Pump capacity, l/h | 100 |
| Pump performance when tested on a vehicle with a 1/2 full fuel tank for 30 sec, cm³ | 750 |
| Working voltage, V | 7—15 |
| Current consumption, no more than, A | 4,7 |
Fuel filter
Characteristic | Meaning |
| Brand | Purolator |
Type: | |
| GF 140/1 |
| GF 140/1 |
| GF 148 |
| Brand and catalog number Bosch | 0 438 060 043 |
Fuel storage tank
Characteristic | Meaning |
| Brand and catalog number ("230") | Bosch 0 580 254 982 |
| Chamber volume, cm³ ("280") | 20 |
Residual pressure, kg/cm² | |
| 1,7—2,4 |
| 5,0 |
Mixture regulator
Characteristic | Meaning |
Brand and catalog number | |
| Bosch 0 438 040 088 and 0 438 060 025 |
| Bosch 0 438 040 009 and 0 438 060 043 |
Air flow meter
Characteristic | Meaning |
| Brand and catalog number | Bosch 0 438 120 158 and 0 438 120 086 |
| Color index | yellow-violet |
Fuel dispenser
Characteristic | Meaning |
| Brand and catalog number | Bosch 0 438 100 108 |
Injection nozzles
Characteristic | Meaning |
Brand and catalog number | |
| Bosch 0 437 502 006 |
| Bosch 0 437 502 007 EP/LKE 7 |
| Injection start pressure, kg/cm² | 2,7—3,8 |
| Fuel spray cone angle ("280") | 35° |
Electromagnetic starting nozzle
Characteristic | Meaning |
Brand and catalog number | |
| Bosch 0 280 170 410 |
| Bosch 0 280 170 405 and 0 280 170 411 |
| Nominal voltage, V | 12 |
Working pressure, kg/cm² | |
| 4,5 |
| –4,5 |
| Working voltage, V | 7—15 |
| Power consumption, W | 37 |
| Fuel spray cone angle ("280") | 80° |
| Fuel injection volume, cm³/min | 95—135 |
Thermal time relay
Characteristic | Meaning |
| Brand and catalog number | Bosch 0 280 130 214 and 0 280 130 220 |
| Nominal voltage, V | 12 |
| Contact opening temperature, °C | +35 |
| Duration of switching on, no more than, s | 8 |
Cold Engine Start Relay
Characteristic | Meaning |
| Brand and catalog number | Bosch 0 332 003 028 |
Control pressure regulator
Characteristic | Meaning |
| Brand and catalog number | Bosch 0 438 140 005 |
| Nominal voltage, V | 12 |
| Maximum allowable voltage (briefly), IN | 20 |
| Working voltage, V | 7—15 |
Additional air supply valve
Characteristic | Meaning |
Brand and catalog number | |
| Bosch 0 280 140 134 |
| Bosch 0 280 140 100 |
| Minimum voltage, V | 12 |
| Maximum allowable voltage (briefly), IN | 20 |
| Working voltage, V | 7—15 |
L-Jetronic fuel injection system
The engines of the 280E cars used the L-Jetronic electronically controlled intermittent fuel injection system from Bosch.
The principle of operation of the fuel injection system
The electric fuel pump takes fuel from the tank and delivers it under pressure of about 2.5 kg/cm² through a fine filter to the distribution line, connected by hoses to each engine cylinder. Installed at the end of the distribution line, the fuel pressure regulator maintains constant injection pressure and drains excess fuel into the tank, i.e. it ensures fuel circulation in the system and eliminates the formation of fuel vapors in it.
The amount of fuel injected is determined by the electronic control unit depending on the volume and temperature of the incoming air, the crankshaft speed and engine load, as well as the temperature of the coolant. The main parameter determining the fuel dosage is the volume of air intake measured by the air flow meter. The incoming air flow deflects the pressure disk, overcoming the force of the spring, and shifts it to a certain angle, which is converted into electrical voltage by means of a potentiometer. The corresponding electrical signal is transmitted to the control unit, which determines the required amount of fuel at a given moment of engine operation and sends pulses of fuel supply time to the electromagnetic valves of the injectors. Regardless of the position of the intake valves, the injectors simultaneously inject fuel twice per each revolution of the camshaft. If the intake valve is closed, the fuel collects in the space in front of the valve and is sucked into the cylinder the next time it opens, simultaneously with the air.
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.
The L-Jetronic fuel injection system consists of the following main elements:
- bosch pressure regulator, catalog numbers 0 280 160 014, 0 280 160 213;
- electronic control unit Bosch, catalog numbers 0 280 001 108, 0 280 001 300;
- bosch coolant temperature sensor, part number 0 280 130 023;
- bosch thermal time relay, catalog numbers 0 280 130 219, 0 280 130 214;
- bosch air flow meter, part numbers 0 280 203 002, 0 280 202 015 (normal air flow at 980 mbar and 20°C, mm³/h: 550);
- air temperature sensor;
- bosch throttle switch, part numbers 0 280 120 206, 0 280 120 302 (permissible opening angle of the idle contact: 90°; full load contact opening angle: 60°);
- two additional resistors;
- bosch electromagnetic injection nozzles, catalog numbers 0 280 150 152, 0 280 150 203 (injection start pressure, kg/cm²: 2.0—3.0);
- bosch electromagnetic starting injector, catalog no. 0 280 170 032 (working pressure, kg/cm²: 2.0—3.0);
- exhaust gas oxygen concentration sensor;
- bosch electric fuel pump, part number 0 580 464 013;
- relay.
Data for adjustment
Characteristic | Meaning |
| Engine crankshaft speed at idle, rpm | 900±50 |
| Carbon monoxide (CO) content in exhaust gases, not more than, % | 0,5—2,0 |
Tightening torques of main threaded connections, kgf·m
Connection type | Meaning |
| Fuel supply pipe nipple, thread M 14x1.5 (maximum residual moment on the body), no more | 1,5 |
| Fuel drain pipe nipple, thread M 12x1.5 | 3,0 |
| Coolant temperature sensor | 1,5 |
| Thermal time relay, no more than | 3,0 |
| Nozzles (on the intake manifold), thread M 6x16 | 0,9—1,1 |