Electric Fuel Pump Operation - Triumph TR7 Owner's Manual

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