Fuel Pump: Description and Operation

Fuel pump, (1989-)




On model year 1989 and later cars, all Saab 900i/S models with a B202 engine have been fitted with a fuel pump of new design. It is of ejector type. The pump is clamped between the top and bottom of the tank, located by ribs on the bottom of the tank and secured at the top by means of a screw top (7). Any flexing of the tank is absorbed by the fuel pump spring element (9).




The design of the tank has been modified to accommodate the new pump. The pump cannot be fitted in fuel tanks of earlier pattern.

The principle of operation of the pump is basically the same as in earlier pumps having a main pump and a teed pump. However, in the new fuel pump the feed pump has been replaced by an ejector pump which is driven by the flow of return fuel.




The function of the ejector pump is to ensure the main pump with a supply of fuel. Owing to the location of the main pump in the reservoir, the supply of fuel to the engine is maintained during cornering and acceleration, even when only a small quantity of fuel remains in the tank.




The pump unit, with the ejector pump at the bottom, is seated in a sump in the bottom of the tank. This ensures that the ejector pump will not run dry, even when only a small amount of fuel remains in the tank and when the car leans over heavily.

When the fuel system is completely drained and the tank is empty, at least five liters of fuel must be poured into the tank before any of it can run into the reservoir.




The engine is always supplied with fuel in the following situations:

1 The car is tilted 1O% to the front and 1O% to the left. Quantity of fuel at least five liters.

2 The car is tilted 1O% to the right. Quantity of fuel at least 13 liters.

3 The car is standing on a level surface. Quantity of fuel 2.6 liters.

4 When the car is tilted to the left, the space where the pump is located fills with fuel so the engine can be supplied with fuel until the tank is as good as empty.