User's Manual

8 Service work Thermo 90 S / Thermo 90 ST
806
The fuel extractor should 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 important 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.
Fig. 806 Webasto fuel extractor
8.6.2.2 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.
NOTE
Cut Mecanyl lines without burr and do not crush them. Do
not cut them with side-cutting pliers.
Since the lines normally cannot be routed with a constant
rising gradient, the internal diameter must not be allowed
to exceed a certain size. Air or gas bubbles will
accumulate in lines with an internal diameter of more than
4 mm and these will cause malfunctions if the lines sag or
are routed downwards. The diameters specified in
Figs. 802 and 806 will ensure that bubbles do not form.
The lines should not be routed downwards from the
metering pump to the heater.
Unsupported fuel lines must be secured to prevent them
sagging. They must be installed in such a way that they
cannot be damaged by flying road chippings and high
temperatures (exhaust line).
The fuel lines must be secure at the connections using
hose clips to prevent their slipping.
Connecting two pipes with a hose
The correct procedure for connecting fuel lines with
hosing is shown in Fig. 807.
NOTE
Ensure that there are no leaks.
Fig. 807 Pipe/hose connection
to engine
from tank
to metering pump
Correct
Wrong
Clip
Bubble Bubble