520i Fuel Injection System Specifications (BMW 5 Series E12)

Kugelfischer injection system

Injection pump brand and type: Kugelfischer PL 04-124 01 C1.

Brand and type of injection pump drive belt: Synchroflex 12 T 5/750.

Oil pan capacity: 100 cm³ (motor oil SAE 10-SAE 20)

The content of carbon monoxide (CO) in exhaust gases is less than 4.5%.

Nozzles

Brand and type: Kugelfischer DLO-20 D.

Injection start pressure, kg/cm²: 30-38.

K-Jetronic injection system

Since October 1975, the BMW 520i with a four-cylinder engine and the 520i with a six-cylinder engine have been equipped with the K-Jetronic mechanical continuous fuel injection system from Bosch.

Operating principle of the fuel injection system

The fuel pump takes fuel from the fuel tank and feeds it into the accumulator to maintain the fuel pressure in the system within 1.5-2.4 kg/cm². Fuel is fed under pressure through the filter to the fuel dispenser-distributor.

The pressure disk of the air flow meter, which is fixed 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 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.



Control pressure regulator (or a regulator of the working mixture composition when warming up the engine) reduces the pressure on the distributor plunger during engine warm-up. Reducing the control pressure with the same air flow leads to an increase in fuel supply and, consequently, to an 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.

Data for adjustment

Fuel pressure in the system, kg/cm²: 4.5-5.2.

Control pressure, kg/cm²:

• on a cold, non-running engine: see graph;
• on a warm, non-running engine: 2.7-3.1;
• when the warm engine is idling: 3.4-3.8.

Crankshaft speed at idle, rpm: 900±50.

Carbon monoxide (CO) content in exhaust gases, %: < 3.

Fine fuel filter

Brand and type: Purflux GF 140 1.

Mixture regulator ("520i" with 6-cylinder engine):

• Brand and type: Bosch 0 438 060 043.

Fuel dispenser

Brand and type:

• "520i" with 4-cylinder engine: Bosch 0 438 120 018;
• "520i" with 6-cylinder engine: Bosch 0 438 100 108.

Air flow meter

Brand and type:

• "520i" with 4-cylinder engine: Bosch 0 438 120 018;
• "520i" with 6-cylinder engine: Bosch 0 438 120 158.

Control pressure regulator

Brand and type: Bosch 0 438 140 005.

Injection nozzles

Brand and type:

• "520i" with 4-cylinder engine: Bosch 0 437 502 007;
• "520i" with 6-cylinder engine: Bosch 0 437 502 006.

Injection start pressure, kg/cm²:

• "520i" with 4-cylinder engine: 3.3;
• "520i" with 6-cylinder engine: 2.7-3.8.

Electromagnetic starting nozzle

Brand and type:

• "520i" with 4-cylinder engine: Bosch 0 280 170 402;
• "520i" with 6-cylinder engine: Bosch 0 280 170 411.

Working pressure, kg/cm²:

• "520i" with 4-cylinder engine: ~4.7;
• "520i" with 6-cylinder engine: 4.5.

Performance, cm³/min ("520i" with 6-cylinder engine): 95-135.

Thermal time relay

Brand and type:

• "520i" with 4-cylinder engine: Bosch 0 280 130 202;
• "520i" with 6-cylinder engine: Bosch 0 280 130 214.

Contact opening temperature, °C: +35.

Duration of switching on, no more than, s: 8.

Cold Engine Start Relay

Brand and type: Bosch 0 332 003 028.