T
HERMO
90 / 90 S
8SERVICING
8-5
8.6.2.2 Fuel lines
Fuel lines may only be steel, copper, or plastic lines
made of unhardened, light and temperature stabilized
PA 11 or Pa 12 (e.g. Mecanyl RWTL) according to
DIN 73378.
As in most cases, if a permanently rising fuel line routing
cannot be ensured, the inner diameter must not exceed a
certain value. Starting from an inside diameter of 4 mm
(5/32 in.), air or gas bubbles accumulate resulting in
malfunctions should the lines be descending or having sags.
The diameters specified above (2 mm) ensure a non-
accumulation of air bubbles.
A descending line routing from the fuel dosing pump to
the heater should be avoided.
Loose fuel lines must be secured in order to avoid
sagging. The installation must ensure protection against
stone impacts and undue temperatures (exhaust line).
The fuel line joints are to be secured against loosening
with hose clamps.
Connection of 2 Pipes with Hose
The proper connection of fuel lines with hoses is shown
in Fig. 8-4.
8.6.3 Fuel Dosing Pump
The fuel dosing pump is a combined delivery, dosing,
and shut-off system and is subject to certain installation
criteria (see Figs. 8-2 and 8-5).
8.6.3.1 Installation Location
It is advantageous to mount the fuel dosing pump in a
cool location as near as possible to the fuel tank. The
ambient temperature must never exceed +20 °C (68 °F)
for gasoline and +40 °C (104 °F) for Diesel installations
at any time while in operation. The maximum pressure at
the tapping location must be below 1.5 bar (21.75 psi.).
Fuel dosing pump and fuel lines must not be installed in
locations exposed to heat radiated by hot vehicle
components. A heat shield is to be provided as required.
Fig. 8-4 Pipe/Hose Connection
Fig. 8-5 Fuel Dosing Pump, Installation Location
and Attachment
