Technical data

Fuel supply Thermo 90 S / Thermo 90 ST

6.2. Vehicles with petrol engines

The heater must be integrated into the return line of fuel systems in

carburettor and injection engines with a return line.

In carburettor engines without a return line the heater must be integrated

into the fuel system in the supply line between the fuel tank and the

vehicle pump.

NOTE

A fuel feed line can normally be identified by the fact that a fuel filter is

installed in it.

NOTE:

If there is an evaporation tank in the vehicle’s fuel system, the fuel must

be extracted upstream of the evaporation tank.

Fuel may only be taken from the supply or return line using the special

Webasto fuel extractor (see Figure 7).

The fuel extractor must be fitted in such a way that any air or gas

bubbles are automatically discharged towards the tank (see Figure 7).

Air or gas bubbles may be produced in the vehicle’s fuel line if there are

leaks in the carburettor or vehicle fuel pump or if the ambient

temperature is higher than the evaporation temperature of the fuel.

The fuel extractor must not be located near the engine, as gas bubbles

may form in the lines on account of heat radiated from the engine. This

may cause problems during combustion.

When installing the heater in a vehicle with fuel injection system, it is im-

portant to establish whether the fuel pump is located inside or outside

the tank. If the fuel pump is located inside the tank, fuel can only be

extracted from the return line. In this case it must be ensured that the

return line continues almost to the bottom of the tank and is not sealed

by a non-return valve. If this is not the case the return line may be

extended.

If the fuel pump is installed outside the tank, the fuel connection may be

made between the tank and the fuel pump.

6.3. Fuel lines

Only steel, copper and plastic lines of plasticised, light and temperature-

stabilized PA 11 or PA 12 (e.g. Mecanyl RWTL) pursuant to DIN 73378

may be used for the fuel lines.

Fig. 7: Webasto fuel extractor

to metering pump

to engine

from tank