Webasto BBW 46, Installation Instructions Manual, Page: 8 / 18

Fuel Supply
Details on the permissible pressure at the fuel extraction
point are contained in the table below.
Permissible
fuel feed height H (m)
at max. permissible
overpressure (bar) in fuel
line
0.00 1.5
1.25 1.4
2.50 1.3
3.75 1.2
5.00 1.1
6.25 1.0
7.50 0.9
8.75 0.8
10.00 0.7
Permissible fuel suction
height S (m)
at max. permissible
underpressure (bar) in fuel
tank
petrol diesel
0.00 -0.15 -0.15
0.50 -0.11 -0.11
1.00 – -0.07
NOTE
A fuel flow line can usually be identified by the in-line fuel
filter.
NOTE:
If the vehicle’s fuel system is equipped with a vapour sep-
arator, fuel extraction is to take place upstream of same.
For fuel extraction from flow or return lines it is
imperative
that the special Webasto fuel pick-up (see Fig. 10) be
used.
The fuel pick-up is to be mounted so that any air or gas
bubbles that may form are automatically discharged to-
ward the tank (see Fig. 10).
Air or gas bubbles in the fuel line of the vehicle can form if
there is a leak in the vehicle’s carburettor or fuel pump, or
if the ambient temperature exceeds the evaporating tem-
perature of the fuel.
Fuel should not be extracted in the vicinity of the engine
since here gas bubbles are likely to form in the lines owing
to the heat radiating from the engine, which may result in
malfunctions of the combustion operation. l
1
+ l
2
≤
13 m
l
1
≤
3 m
l
2
≤
10 m
l
2
l
1
l
2
l
1
Fig 9: Fuel Supply
to metering pump
to engine
from tank
Fig 10: Webasto Fuel Pick-Up
BBW 46 / DBW 46
6