General information and safety precautions: power supply system (Skoda Yeti 5L)

Fuel supply

Petrol models

The fuel system consists of a rear-mounted fuel tank with a filler neck, a fuel supply module with a fuel gauge, a fuel gauge #2 with a jet pump, a carbon fuel vapor absorber, fuel lines, a fuel filter, and an electronic fuel injection system controlled by an electronic engine control unit (ECM). The fuel injection system consists of a high-pressure fuel pump, a fuel distribution line, and injectors.

The fuel tank contains a fuel supply module, which is an assembly of a fuel level sensor and a fuel pump with a mesh filter. The fuel gauge is designed to display the fuel reserve on the instrument cluster. The electric fuel pump is designed to create pressure in the low-pressure part of the fuel supply system. Switching on/off and the performance of this pump (depending on the crankshaft speed and engine operating mode) the corresponding control module "J538" operates via a PWM signal, operating on the basis of information from the ECM. The mesh fuel filter is designed for the entire service life of the vehicle and does not require replacement.

The jet pump is designed to pump fuel to the fuel supply module from another part of the tank. The fuel reserve sensor No. 2 built into the jet pump is designed to provide more accurate information about the fuel reserve.

In the event of an accident, the fuel shut-off function may be activated to reduce the risk of ignition of leaking fuel. This function disables the fuel pump at the level of its relay.



To improve engine starting performance, the fuel pump relay is activated for two seconds when the driver's door is opened to pre-pressurize the fuel supply system. Therefore, for safety reasons, when repairing without disconnecting the battery, the fuel pump control unit connector should be disconnected.

To ventilate the fuel tank, vent valves are used to remove fuel vapors to the EVAP system canister (see Part B).

The high-pressure fuel pump is designed to create high fuel pressure to implement the principle of direct fuel injection. The fuel injection pump is driven via a pusher from the camshaft.

Fuel from the high-pressure fuel pump accumulates in the fuel distribution line, equalizing its pressure, and is then injected directly into the combustion chambers through injectors. The moment and duration of fuel injection are determined by the ECM using signals from various sensors (see Section 2).

The location of the power supply system components is shown in Illustrations 1.1a-b.

Diesel models

The fuel supply system consists of a rear-mounted fuel tank with a filler neck, a fuel supply module, fuel lines, a fuel cooler, a fuel filter, an additional fuel pump, and an electronic sequential distributed fuel injection system controlled by an electronic engine control unit (ECM). The distributed sequential fuel injection system consists of a high-pressure fuel pump (HPFP), a fuel distribution line "Common Rail", piezo injectors, fuel pressure pipes and fuel return lines.

The location of the fuel system components is shown in Figure 1.2. The fuel supply system diagram is shown in Figure 1.3.







The fuel delivery module is an assembly of the electric booster pump and fuel level sensor and also provides connections for delivering fuel to the auxiliary heater (see chapter 3). The electric booster pump is designed to continuously supply fuel from the tank to the filter. The fuel reserve is displayed on the instrument cluster (see chapter "Controls and operating techniques").

The fuel filter protects the fuel supply system from contamination by water and other foreign particles and, therefore, from premature wear. The fuel filter must be replaced periodically (see Section 23 Chapter 1). The filter has a built-in preheating valve, which prevents the filter from becoming clogged with crystallizing paraffins at low ambient temperatures.



The additional fuel pump is designed to supply fuel from the low-pressure circuit to the high-pressure fuel pump under a pressure of at least 5 bar, which is necessary for the operation of the high-pressure fuel pump in any mode. This vane type pump is controlled by a relay from the ECM. If the auxiliary pump fails, the engine power is reduced and it cannot be started.

A mesh filter and fuel temperature sensor "G81" are installed between the additional fuel pump and the high-pressure fuel pump.

The injection pump, driven by the timing belt from the crankshaft, increases the fuel pressure to a maximum of 1800 bar and delivers it through one pipe to the fuel distribution line, where the fuel pressure is equalized for all injectors and monitored by the fuel pressure sensor.

High fuel pressure is regulated by the so-called "dual regulation algorithm": depending on the engine operating mode, either through the fuel pressure regulator valve or through the fuel metering valve. The valves are controlled by the engine control unit using a pulse-width modulated (PWM) signal.

Adjustment via the fuel pressure regulator valve is carried out when starting the engine and to warm up the fuel. For good mixture formation in the combustion chamber with a small ignition delay, a high fuel temperature is required. To quickly heat the fuel when the engine is cold, the high-pressure fuel pump supplies and compresses more fuel than necessary, and the excess heated fuel is fed back through the pressure regulator valve and the return fuel line. If the fuel pressure regulator fails, the engine cannot operate because the pressure required for fuel injection cannot be created.



Adjustment via the fuel metering valve is carried out at high injection volumes and high pressure in the fuel distribution line. This reduces the power consumption of the fuel injection pump and prevents unnecessary heating of the fuel. If the fuel metering valve fails, engine power is reduced and the engine management system operates in emergency mode.

Pressure fuel lines (metal tubes) manufactured with pre-set lengths and bending radii in the required places; such fuel lines should be installed in such a way that they are not subject to any stress.

The injectors inject fuel under high pressure directly into the combustion chambers. The moment and duration of fuel injection are determined by the ECM unit based on signals from various sensors (see Section 2).

Excess fuel from the injectors is returned to the fuel tank through the injector return lines, pressure holding valve and fuel pump. The fuel pressure holding valve is designed to maintain the pressure in the return lines of the injectors, which is necessary for the operation of the injectors. Do not disconnect the fuel pressure holding valve while the engine is running to avoid damaging the injectors. The return fuel lines of the injectors are replaced only together with the pressure holding valve. If the fuel retention valve and injector fuel return lines have been replaced, after starting the engine, allow it to idle for approximately two minutes to bleed air from the fuel system.

Fuel injection system with fuel distribution rail "Common Rail", compared to the injection system with a distributor fuel injection pump, it has the following distinctive features:

• injection pressure can be freely selected and adapted to the corresponding engine operating mode;
• high injection pressure (up to 1800 bar) creates conditions for good mixture formation;
• flexible batch injection process with multiple pre- and post-injections;
• low fuel consumption;
• low level of emissions of harmful substances;
• smooth engine running.

Injection system "Common Rail" assumes a variety of injection control algorithms in order to adapt the pressure and injection process to the engine operating mode. At the same time, such a system fully complies with the ever-increasing requirements for reducing fuel consumption, reducing the level of emissions of harmful substances and increasing the smoothness of the engine.

To improve engine starting performance, the fuel pump is activated for two seconds when the driver's door is opened to pre-pressurize the fuel supply system. Therefore, for safety reasons, when repairing without disconnecting the battery, the fuel pump relay fuse should be removed or the fuel delivery module connector should be disconnected.

Fuel Saving Tips

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 gear possible for the given speed.

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.

Air supply

Petrol models

The air supply system includes an air intake, an air cleaner, a turbocharger with an intercooler (on 1.2 and 1.4 l engines an additional intercooler radiator is used), throttle valve and intake manifold.

An electronically controlled throttle valve, controlled by the accelerator pedal position sensor and the ECM, is used to regulate the air supply. The throttle valve is driven by an electric motor based on a signal from the gas pedal position sensor. The throttle position is controlled by the TPS sensor.

To determine the air flow on 1.2 and 1.4 l engines, the following are used:

• boost pressure sensor "G31", combined with intake air temperature sensor No. 2 "G299" (1ATNo. 2);
• intake manifold pressure sensor "G71", combined with IAT sensor "G42".

On 1.8 l engines, the following are used to determine air flow:

• sensor "G42" IAT;
• mass air flow sensor "G70" (MAF), combined with IAT sensor No. 2 "G299".

All petrol engines use turbocharging with charge air cooling (intercooler).

The turbocharging diagram of the 1.8 L engine is shown in Figure 1.2. The turbocharger consists of two elements (turbines and compressors), mounted on one shaft and enclosed in a common housing. The turbocharger bearings receive oil for cooling and lubrication from the engine through the oil supply line. The oil returns to the crankcase through the return oil line. The turbocharger and exhaust manifold are combined into one non-separable unit and are not supplied separately.



The turbocharger increases the pressure of purified atmospheric air, thereby increasing the amount of air entering the cylinder in one cycle. With more oxygen, more fuel can be burned. Thus, with the same working volume and rotation speed characteristics, better power figures are achieved. The air heated in the turbocharger passes through the intercooler, where it is cooled. When cooling, the air density increases and, since more oxygen enters the combustion chambers, an additional increase in power occurs. The wastegate controls the amount of air supplied to the turbocharger. The N75 boost pressure limiting solenoid valve is an electropneumatic device. This valve regulates the vacuum by which the guide vane control mechanism operates. When the "N75" valve fails, the vacuum required for the vacuum drive to operate is not created and the vacuum drive spring sets the control rod to a position where the turbine guide vanes are oriented at a large angle (emergency mode). In this case, at low engine speeds and therefore at low exhaust pressure, only low boost pressure is possible; the engine power is insufficient and active regeneration of the diesel particulate filter is not possible.

Diesel models

Air sucked from the atmosphere passes through the air purifier. The air purifier filter element must be replaced periodically (see Section 16 Chapter 1).

All diesel engines use turbocharging with charge air cooling (intercooler). The operating principle of a turbocharger is described in the "Gasoline Engines" subsection above.

Vacuum is used to control the operation of the turbocharger. The diagram of the control vacuum lines is shown in Figure 1.5.



The air supply tract also includes the EGR and PCV systems (see Part B).

In the direction of flow, before the intake manifold, before the EGR valve input, the throttle valve unit "J338" is installed. It contains an electric motor, which smoothly controls the position of the valve via a gearbox depending on the load and engine speed. The throttle valve drive has a built-in throttle position sensor, designed to implement feedback from the engine management system. The throttle valve block has the following purpose.

In some modes, the throttle valve is used to create a pressure differential between the intake tract and the EGR circuit. This pressure differential helps the EGR system operate more efficiently.

In DPF regeneration mode, the throttle valve regulates the inlet air flow.

When the engine is turned off, the damper closes, gradually reducing the amount of incoming air to smoothly stop the engine.

If the throttle valve unit fails, correct control of the exhaust gas recirculation process and active regeneration of the particulate filter become impossible.

Ensuring safety and maintaining cleanliness when working with the fuel supply system

Caution: Fuel injection equipment is manufactured to very precise tolerances and very close clearances, so absolute cleanliness is especially important when working with these components. Be sure to plug any open holes or lines.

Caution: When loosening and tightening the union nuts securing the fuel pressure lines, simultaneously press the flared end of the fuel line against the injector and remove (suck) vacuum to prevent dirt from entering the fuel system. Avoid allowing the union nuts to strike the flared edges of the new fuel lines as this may damage the lines and introduce foreign particles into the lines. Close the holes formed after disconnecting the tubes 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.

Before working on the fuel system, always disconnect the negative battery cable to avoid sparks. Before disconnecting the battery, you should read the fault codes (see Chapter 5).

Ensure proper ventilation of the workplace - fuel vapors are toxic.

Before working on the fuel supply system of petrol models, fuses SD14 and SD30 should be removed to prevent the fuel pump from turning on when the driver's door is opened.

Avoid contact with rubber or leather surfaces as this may damage them.

The fuel system is under pressure and fuel may escape if opened, so wear safety glasses. Wipe up any spilled fuel with a rag.

Hose connections are secured using tape or clamp clamps. When disassembling, the clamping clamps should be replaced with band clamps.

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 clean 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.