Direct Petrol Injection System with Bosch Motronic MED 7 - Volkspage

This is how it works
Inlet with fine gauge strainer from fuel rail
During the injection cycle, the magnetic coils in
the injector are activated and a magnetic field is
induced. The magnet armature and the valve
needle pick up, the valve opens and fuel is
injected.
If the coil is no longer activated, the magnetic
field collapses and the valve needle is pushed
into the valve seat by the pressure spring. The
fuel flow is blocked.
Electrical
connection
pressure spring
Solenoid
Teflon sealing ring
Valve needle with magnet armature
Valve seat
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Outlet bore
Activating high-pressure injectors
High-pressure injectors are activated by an
electronic circuit in the engine control unit.
In order to ensure that the injector opens as
quickly as possible, a voltage of approximately
90V is applied to the valve after it is briefly
premagnetised. The result is a current intensity of
up to 10A. If the valve is fully open, a voltage of
30V and a current intensity of 3-4A are sufficient
to hold the valve in the fully open position.
Current (I)
Needle lift (µm)
Pickup current
Pre-exciter current
Holding current
Injection time (t)
Injection time (t)
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Failure strategies
A defective injector is recognised by the
misfire detector and no longer activated.
After renewing an injector, the learnt
values must be cleared and re-adapted to
the engine control unit. Please refer to the
relevant Workshop Manual.
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