Downloaded from www.Manualslib.com manuals search engine Injection Systems
Multi PointSimultaneousInjectors receive pulses from E.C.U. twice per engine cycle.
( Corsa 13 NE, 16NE, Astra 14SE, 16SE, 18XE, 20SHE )
SequentialInjectors are pulsed by E.C.U. once per engine cycle as per spark
plug firing order. ( Astra 20XE )
GroupedInjectors pulsed in groups or banks, once or twice per cycle
depending on system design
Single PointThrottle BodySingle injector mounted on throttle body pulsed as per engine
requirement ( Astra 160 TBI )
Operation
Injectors on the Bosch Motronic engine management systems receive battery voltage and are
triggered by the E.C.U. depending on the signals received from the various sensors attached
to the engine. Fuel pressure is constant (M.P.F.I. – 250 to 300 Kpa).
Injector opening frequency (Hz) and duration (pulse width) determine the amount of fuel
being delivered to the combustion chamber. Variations in pulse width and frequency ensure
that adequate fuel is supplied for efficient engine operation.LONGER PULSE WIDTH= RICHER MIXTURESHORTER PULSE WIDTH= LEANER MIXTURE
Pulse rate and width will increase with increased engine rpm and load.
Duty Cycle
Duty cycle is the combination of pulse width and pulse rate, and is expressed as a percentage
of time “ON” and time “OFF” eg. If an injector was on for 10ms and closed for 90ms, the
duty cycle “ON” is 10% and the duty cycle “OFF” is 90%. The total on and off duty cycle
reading should be 100%.
CrankingInjector duration is longer during cranking (richer mixture) for easier startingand to promote warm-up.
IdlingInjector duration is longer at start-up if engine is cold, and graduallydecreases as engine warms up.
AccelerationInjector duration is longer at initial acceleration to prevent “flat spot”RunningInjection pulse is controlled by the E.C.U. depending on the signals receivedfrom the various engine sensors.
Downloaded from www.Manualslib.com manuals search engine TESTING INFORMATION AND TEST PROCEDURES
Typical Simultaneous Injection Duration
Engine ColdMs
Cranking ------------------------------------------>4
Idle -------------------------------------------3.5 to 4
Engine Warm
Idle---------------------------------------------2.5
1000rpm2.3*
20002.1*
30002.0*
Snap Throttle>7Sequential injection systems will be less than twice the above values due to single pulsingper engine cycle.
NOTES.THE USE OF A 4 GAS ANALYSER CAN GREATLY AID DIAGNOSTICDIRECTION AND TIME.
Comparing mixture content to injector pulse width can identify components and systems to
be tested in a logical sequence.
Example :A rich mixture could indicate high fuel pressure, incorrect manifold pressure,
incorrect coolant temp, etc,etc.
D.N. 12/97* Gradually leans out,depending on load
