Triumph TR7 - Electric Fuel Pump Operation

EMISSION AND EVAPORATIVE LOSS CONTROL SYSTEMS
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Fig. 7 Electric fuel pump
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Electric Fuel Pump Operation
The fuel pump IS energIsed, .ndependant of the electrOniC
control
Unit, from an output terminal on the combined relay
The combined relay IS the component that prOVIdes an
interface between the
main vehIcle electrical harness and
those ,tems that are spec,f,cally related to the electrOniC fuel
injectIOn system. An inertia SWItch .s Included In the CirCUit to
Isolate the fuel pump and prevent
II from operattng In the
event of an Impact type
accident The CIrCUit is also routed
through the electrOniC control system Air Flow Meter where a
simple contact
SWitch ensures that the fuel pump cannot
operate when
no air IS flOWing mto the engine i,e the engine
is no! running. ThiS contact SWitch IS by-passed when the
starter motor
CirCUit IS energised
Once the
engine IS runnmg a ClrCUlt from the Ignl\lon SWitch
passes through a relay ,aground,via the electroniC control Unit
on TAl models When energised th.s relay permIts a CIrCUIt
to be made to the AIr Flow Meter contact SWItch ProvIding
the contact switch
IS closed a CirCUit IS completed through a
second relay,
again to ground. When energised thiS second
relay completes the
CirCUIt to operate the fuel pump
Under engme starting conditions the Air Flow Meter contact
switch would normally Isolate the fuel
pump as no air IS
flowing through the engine. To overcome thiS an Input IS
taken direct from the starter motor CirCUit to energise the
second relay and thus
permit the fuel pump to operate during
the engine starting operation
8
Fig. 8 Circuit principles of fuel pump operation