Fuel System, Petrol: Overview Saab 9-3 I

Identifying Fuel Tank. Scheme 8

FUEL TANK TECHNICAL DATA

Brief Description

The fuel system on the Saab 9-3 operates through an electric fuel pump drawing fuel from the fuel tank and building up fuel pressure in the system. The pressure level is determined by the pressure regulator, which maintains a constant fuel pressure relative to the pressure in the engine intake manifold. In this way, the amount of fuel injected is not affected by the varying pressure in the intake manifold but is determined only by the opening duration of the injectors.

Fuel is supplied to the engine through injectors (electrically controlled solenoid valves) mounted in the intake manifold close to the intake valves and coupled together via a common fuel rail.

Identifying Fuel Pump Components. Scheme 9

Fuel pump

1. Pump
2. Ejector
3. Filter
4. Reservoir
5. Pump line
6. Return line
7. Pump cover
8. O-ring
9. Spring
10. Screw ring

The fuel pump is located inside a plastic reservoir that is fixed between the top and bottom of the tank. It is centered on ribs on the bottom of the tank and secured to the top of the tank with a screw ring (10).

Movement in the tank is taken up by the fuel pump spring (9). In principal, the design and function of the pump is no different to that of earlier fuel pumps with a main and feed pump. In the Walbro pump, however, the feed pump has been replaced by a positive ejector that is "driven" by the fuel flowing from the delivery line via a T-piece. The pump is an electric rotor type pump.

Fuel pump location in tank

The ejector is used to secure the supply of fuel to the pump. Thanks to it being located in the reservoir, the pump is guaranteed a flow of fuel even during cornering and acceleration with small amounts of fuel in the tank. The pump and motor are encapsulated and cannot be dismantled for repair.

A non-return valve on the pressure side of the pump, located in the connector nipple in the pump cover, prevents the pressure in the fuel line from dropping as soon as the engine is turned off.

Identifying Fuel Filter. Scheme 10

The fuel filter is located in the delivery line between the fuel pump and the fuel rail at the front of the fuel tank on the right-hand side. The fuel filter is protected by a cover.

The filter is used to remove impurities in the fuel and prevent the injectors from clogging up.

The filter contains a paper element with a mean porosity of 5 mue, followed by a strainer to catch any loose fragments of paper. A support plate fixes the position of the filter in the metal housing. The efficiency of the filter is dependent on how clean the fuel is.

Identifying Fuel Rail Components (B204I/E). Scheme 11

Fuel rail

1. Fuel pressure regulator
2. Fuel rail
3. Injector
4. Clips

The fuel rail distributes equal amounts of fuel to each injector. It also acts as a fuel accumulator. The volume of the pipe in relation to the amount of fuel used during each working cycle is sufficient to prevent variations in pressure. The injectors, which are connected to the fuel rail, are therefore subjected to the same fuel pressure. The design of the fuel rail allows easy injector fitting as the injectors are connected directly to it.

The fuel line and pressure regulator are also connected to the fuel rail.

Identifying Fuel Rail Components (B235R, B205L/R). Scheme 12

1. Fuel pressure regulator
2. Fuel rail
3. Injector
4. Clips

The fuel rail distributes equal amounts of fuel to each injector. It also acts as a pressure equalizer. The volume of the pipe in relation to the amount of fuel used during each injection is sufficient to prevent variations in pressure. The design of the fuel rail allows easy injector fitting as the injectors are connected directly to it.

Fuel lines and pressure regulator are also connected to the fuel rail.

Identifying Pressure Regulator. Scheme 13

Pressure regulator

The pressure regulator is fitted on the left-hand end of the fuel rail (in the direction of travel).

The regulator maintains a constant difference between the fuel pressure and the pressure in the intake manifold. In this way, the injected quantity of fuel is always determined by the length of time that the electromagnetic injector is open.

The pressure regulator is a diaphragm controlled overflow valve set at 3.0 bar. It consists of a metal housing divided into two chambers by a press-fitted diaphragm. There is a coil spring in one of the chambers that presses against the diaphragm and the fuel passes through the other.

If the preset pressure is exceeded, a valve, which is controlled by the diaphragm, exposes an opening to the return line through which excess fuel can flow back to the fuel tank.

The spring chamber in the pressure regulator is connected to the engine intake manifold by a hose after the throttle. This means that the pressure in the fuel system is affected by the absolute pressure in the intake manifold, which results in the pressure drop across the injectors remaining constant at any throttle position.

Identifying Injector. Scheme 14

Injector

The injectors are connected directly to the fuel rail. They are located in the intake passageways in front of the intake valves.

An injector consists of a valve body and spray nozzle with magneto armature. The valve body includes a solenoid winding and actuator for the spray nozzle. The injectors are controlled electronically and are opened and closed by electric impulses from the control module.

Injection valves are available in different versions depending on engine variant.

Identifying Class BE Fire Extinguisher. Scheme 15

1. Work only in a well-ventilated area! If approved equipment for the extraction of fuel vapors is available, be sure to use it.
2. Wear suitable gloves! Prolonged contact with fuel can cause skin irritation or dermatitis.
3. Keep a class BE fire extinguisher close at hand! Beware of sparks caused by short circuits and when connecting and disconnecting leads in electrical circuits.
4. No smoking anywhere in the vicinity.

The fuel tank does not have a bottom plug. When work on the fuel system involves draining the fuel tank, this can be done through the fuel filler pipe using suitable tank draining equipment.