L-Jetronic fuel injection system
On BMW car engines "525i", "528i", "528iA" and the "535i" 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, and 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 throttle valve, 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.
Data for adjustment
Engine crankshaft speed at idle, rpm 900±50.
Carbon monoxide (CO) content in exhaust gases, no more than, %: 0.5-2.0.
The L-Jetronic fuel injection system consists of the following main elements:
- bosch pressure regulator 0 280 160 0141);
- electronic control unit Bosch 0 280 001 1082), installed in the glove compartment;
- bosch coolant temperature sensor 0 280 130 023;
- thermal time relay Bosch 0 280 130 219 3);
- air flow meter Bosch 0 280 203 0024) (normal air flow at 980 mbar pressure and 20°C temperature, mm³/h: 550);
- air temperature sensor;
- bosch throttle switch 0 280 120 2065);
- two additional resistors;
- electromagnetic injection nozzles Bosch 0 280 150 1526) (injection start pressure, kg/cm²: 2.0-3.0);
- electromagnetic starting nozzle Bosch 0 280 170 032 (working pressure, kg/cm²: 2.0-3.0);
- vacuum limiter;
- electric fuel pump Bosch 0 580 464 013;
- relay.
1) 0 280 160 213 for BMW "5251/E28" and "5281/E28".
2) 0 280 001 114 for BMW "535i".
3) 0 280 001 300 for "525i/E28" and "528i/E28", 0 280 130 214 for BMW "535i" and from the 1980 model year on "525i" and "528i".
4) 0 280 202 015 for BMW "525i/E28" and "528i/E28".
5) 0 280 120 302 for BMW "525i/E28" and "5281/E28" (permissible contact opening angle: 90°, full load contact opening angle: 60°).
6) 0 280 150 203 for BMW "525i/E28" and "5281/E28".