Fiat Bravo Quiz
Diesel injection system

Diesel control unit

In this manual: Diesel injection system
Dear Reader — 1Engine — 35Engine lubrication — 3Engine cooling — 10Ignition/spark plugs — 14Fuel system — 10Petrol fuel injection — 13Diesel injection system — 13Exhaust system — 7Clutch — 7Transmission / Gearshift / Automatic Transmission — 5Front Axle — 11Rear axle — 4Steering — 9Wheel alignment — 1Brake system — 22Wheels and tyres — 10Body — 34Heating — 6Electrical system — 39Lighting system — 14Instruments — 7Windscreen wiper system — 8Vehicle care / tools — 6Jump Starting / Towing the Vehicle — 3Jacking up the vehicle — 1Fiat Bravo / Brava Maintenance Schedule — 1Maintenance — 38Wiring diagrams — 5
~2min read
55/74 kW engine (75/100 hp) up to 9/98

All data on engine operating conditions, registered by various sensors, is combined in the diesel control unit. Based on this data, the following systems are controlled for the best possible engine running and low exhaust emission values:
Injection timing control: via the injectors, the diesel fuel is injected into the prechamber of the respective cylinder at the correct time. The control unit adjusts the start of injection according to engine load and air pressure, so that complete combustion takes place and little soot is produced. To help the cold engine start better, the start of injection of the injection pump is advanced, so that the fuel is injected earlier into the hot air.

Fast idle speed: when the engine is cold, a valve on the injection pump is activated, which raises the idle speed and brings the engine to operating temperature faster. On vehicles with air conditioning, fast idle is also switched on when the switched-on A/C compressor loads the engine at idle. The air conditioning is switched off by the diesel control unit if the engine is too hot or high engine output is required (hard acceleration, high engine speed).

Preheating: when the engine is cold, the glow plugs are switched on, see chapter "Diesel glow plug system".

The exhaust gas recirculation (EGR) system is switched on and off by the control unit via a vacuum valve, depending on engine load and engine temperature. EGR principle, see page 118.

The control unit evaluates signals from various sensors: engine speed is picked up from the TDC sensor on the crankshaft, and the accelerator lever position on the injection pump is transmitted via a potentiometer. Start of injection is monitored by a needle lift sensor on the injector of cylinder 1. Coolant and intake air temperatures are measured by sensors. The mass of fresh air flowing into the engine is registered by an air mass meter. Function of the air mass meter, see chapter "Petrol injection".

The control unit detects faults occurring in the injection system and stores them. At a Fiat workshop, the faults can be read out with a diagnostic tester and rectified specifically.

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