On MPI petrol models, the electric fuel pump is designed to create pressure in the fuel system, while on diesel and FSI petrol models, this pump is used to supply fuel from the tank to the high-pressure fuel pump (HPFP) or unit injectors. Fuel is supplied from the tank to the engine via the fuel supply line and fuel filter. The regulator limits the pressure in the supply line to a certain level.
Common Rail injection pump (tDI-CR diesel engines and FSI petrol engines) creates the necessary pressure in the fuel distribution line, common to all nozzles/injectors. On FSI models, the fuel is injected directly into the combustion chambers.
On TDI-PD diesel models, instead of a high-pressure fuel pump, unit injectors are used to create high pressure, each of which has a high-pressure fuel pump built into it.
The carbon canister on gasoline models is part of both the fuel supply system and the EVAP system (see Part B). On diesel models, a carbon adsorber is not used, since diesel fuel is difficult to volatilize, and ventilation of the fuel tank occurs directly into the atmosphere.
The fuel reserve is determined using a lever sensor. On all-wheel drive models, two sensors are used - for each part of the tank.
Driving style has a significant impact on fuel consumption. Below are some tips for saving fuel.
- Once the engine starts, move off immediately, even if it is in cold weather (do not allow a cold engine to run at high speeds and do not drive at high speeds until the engine has warmed up).
- If the vehicle is stopped for more than 40 seconds, turn off the engine.
- Always drive in the highest possible gear.
- When driving long distances, maintain a steady speed whenever possible. Avoid driving at high speeds and do not brake unnecessarily.
- Do not carry unnecessary cargo in your vehicle.
- Check the air pressure in your tires and do not allow the pressure to drop too low.
Safety and cleanliness precautions when working with the fuel supply system
Caution: Fuel injection equipment is manufactured to very precise tolerances and with very small clearances, so absolute cleanliness is especially important when working with these components. Be sure to plug any open ports or lines.
Caution: When loosening and tightening the union nuts securing the fuel pressure lines on diesel models, simultaneously press the flared end of the fuel line against the injector and remove (suck) contamination using a vacuum to prevent dirt from entering the fuel system. Do not allow the union nuts to hit the flared edges of the new fuel pipes, as this may damage them and allow foreign particles to enter the pipes. Close the holes formed after disconnecting the pipes with clean plugs.
Do not work with the fuel system near an open flame, do not smoke or turn on heating devices! Keep a fire extinguisher at hand.
Always disconnect the negative battery cable before working on the fuel system to avoid sparks. Before disconnecting the battery, read the fault codes (see Chapter 5).
Ensure proper ventilation of the workplace - fuel vapors are toxic.
Avoid contact of gasoline with rubber and leather surfaces, as.
they may be damaged. The fuel system is under pressure and fuel may escape when opened - use protective glasses. Collect spilled fuel with a rag.
Hose connections are secured using band or clamp clamps. Clamp clamps should be replaced with band clamps during disassembly.
Clean connections and adjacent areas thoroughly before opening.
Place the removed components on a clean surface and cover with plastic, paper or a lint-free cloth.
Close open nipple connectors, for example with suitable plugs.
Install only clean parts - remove replacement components from packaging immediately before installation. Do not use parts that have been stored without packaging.
Avoid using compressed air when the fuel system is open and try not to move the vehicle if possible.
Do not use sealants containing silicone, as silicone particles that get into the engine do not burn and may cause the lambda probes to fail.
Before removing the fuel tank, pump out the fuel from it using a pump specially designed for this purpose.
Remember that even an empty fuel tank remains explosive.
After installing the fuel system components, start the engine and check all connections for leaks.
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