Page 225 - 05. Subyek Teknik Mesin - Automobile Mechanical and Electrical Systems Automotive Technology Vehicle Maintenance and Repair (Vehicle Maintenance Repr Nv2) by Tom Denton

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Engine systems 209

Pressure relief valve Armature

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Fuel inlet Fuel outlet

Figure 2.265 Roller cell pump: fuel intake
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Roller-cell pump Check valve

Figure 2.264 Roller cell pump

Figure 2.266 Roller cell pump: fuel
discharge

Figure 2.267 Fuel fi lters have been developed to match specifi c needs of system manufacturers

The fuel pump electrical supply is live only when the engine is being cranked
for starting or is running. The fuel pump electric feed is from a relay that is
switched on with the ignition. Safety features are built into the electric control
feed to the relay so that it operates only to initially prime the system or when
the engine is running. The control functions of the fuel pump relay are usually
provided by the fuel control module. A further safety feature is the use of an
inertia switch in the feed from the relay to the fuel pump. This operates, in the
event of an accident, to cut the electric feed to the fuel pump and to stop the
fuel supply. It is an impact-operated switch with a weight that is thrown aside
to break the switch contacts. Once the switch has been operated it has to be
manually reset.
The fuel fi lter is an in-line paper element type that is replaced at scheduled
service intervals. The fi lter uses microporous paper that is directional for fi ltration.
Filters are marked for fuel fl ow with an arrow on the casing and correct fi tting is
essential. They are often matched specifi cally to a vehicle and fuel type, so, as
always, refer to manufacturers’ specifi cations ( Fig. 2.267 ).