The air heater, when used in the ventilation mode of
operation, may also be employed for heating air ducting
without any further accessories. A short circuit of the
heating air flow is to be avoided.
8.6.2 Fuel Supply
Fuel is tapped from the fuel reservoir of the vehicle or
from a separate fuel container. The rated pressure at the
fuel tapping location is shown in Fig. 801.
Permissible fuel feed
At max. permissible
height H (m)
overpressure (bar) in fuel
line
0.00
0.2
1.00
0.11
2.00
0.03
Permissible fuel suction
At max. permissible low
height S (m)
pressure (bar) in fuel tank
0.00
-0.10
0.50
-0.06
1.00
-0.02
8.6.2.1 Fuel Tapping
Vehicles with Diesel Engine
Fuel tapping must be from the fuel reservoir or from a
separate tank (Figs. 802, 803 and 804). This separate
fuel tapping avoids an influence on the pressure.
Vehicles with Carburettor Engine
Fuel tapping in motorcars may only be performed using
the special Webasto fuel tap (e.g. Ident No. 470 910)
possibly in the vicinity of the fuel tank. Connection to the
supply or return line is optional, the return line must be
routed almost to the tank floor, otherwise the return line
may be extended.
The fuel tap is to be mounted so that air or gas bubbles
can escape towards the fuel tank.
The fuel tap should be located in the engine compart-
ment because the radiation of engine heat may cause
gas bubbles to build up in the fuel lines causing malfunc-
tions in the combustion operation.
Vehicles with Fuel Injection Engines
When installing the heater in vehicles with fuel injection
system the fuel pump’s location within or outside the fuel
tank must be investigated first.
If the fuel pump is fitted inside the fuel tank, the fuel may
be tapped only from the return line using the Webasto
fuel tap only (e.g. Ident No. 470 910) ensuring that the
return line is routed almost to the tank floor. If this is not
the case, the Webasto fuel tap (see Fig. 802, 803 and
804) may be used.
In case of a fuel pump mounted externally to the tank
the fuel tap between fuel tank and fuel pump may also
only be fitted using the Webasto fuel tap (e.g. Ident No.
470 910).
max. 3 m
i ø 2 mm
i ø 2 mm
S
H
i ø 2 mm
l
1
l
1
i ø 2 mm
l
2
l
2
HG
HG
Fig. 801 Fuel Supply
l
1
+ l
2
≤
10 m
l
1
≤
1.2 m
l
2
≤
8.8 m
802
8 Servicing
Air Top 2000