Fig. 802 Pipe/Hose Connections; Fig. 803 Installation Position Of Dp40/Dp41 Metering Pump; Connection To Vehicle Fuel System - Webasto Thermo Top V Workshop Manual

Servicing work
A defective circulating pump must be replaced with the
U4847 ECON in accordance with the spare parts list.
Electrical checking of circulating pump
Internal resistance of the circulating pump: 10 ± 1 kohms
In addition, the operation of the pump must be tested as fol-
lows:
When starting the heater, a slight vibration must be felt on
the pump. When controlling with the Webasto Thermo Test
PC Diagnosis with maximum power, a soft pump noise must
be audible.

8.6.2 Connection to vehicle fuel system

The values for the maximum pressure at the fuel extraction
point are listed in following table.
Permissible fuel At max. perm. pressure [bar]
inflow height H
[m]
Petrol
0.00 DP40: 0.30
DP41: 0.10
1.00 DP40: 0.22
DP41: 0.02
Permissible fuel At max. perm. negative pressure
intake height S
[m]
Petrol
0.00 -0.1
0.50 -0.06
1.00 -0.02
Petrol
Pressure line 0 to 6 m
length
Inside hose 2 ± 0.2 mm
diameter
An empty fuel line or larger bubbles in the fuel line or meter-
ing pump can result in a repeat start of the heater with
increased smoke.
802
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NOTE
in the fuel line
Diesel
DP40: 2.00
DP41: 0.10
DP40: 1.92
DP41: 0.02
[bar]
in the fuel tank
Diesel
-0.1
-0.06
-0.02
Diesel
2 to 4 m
2 ± 0.2 mm
NOTE
8.6.2.1 Fuel lines
The hose connections on the connection pieces from the
heater, the metering pump, fuel standpipe and various hose
connection pieces must be executed as shown in Fig. 802.
Mecanyl lines must mounted flush up to the connection
pieces to prevent collections of bubbles.
Correct
Wrong

Fig. 802 Pipe/hose connections

8.6.2.2 Metering pump
It is advisable to install the metering pump in a cool place to
avoid the formation of bubbles during operation. The max-
imum ambient temperature must not exceed +20 °C at any
time during operation.
Y

Fig. 803 Installation position of DP40/DP41 metering pump

For the diesel heater with a solenoid valve, the DP41 (ID No.
9009529_) is used without a zero termination, as a pressure
compensation must be carried out between the closed sole-
noid valve in the heater and the tank (= fuel removal point).
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