After the stabilization phase,
it is possible to select a cylinder / injector using the arrow key
"UP" and then, with the arrow key "DOWN", to switch
off / deactive the injector of each selected cylinder for 3 s.
In addition, the YES and NO keys
can be used to display the various data list parameters. Key F9 is used
to store the data as in the snapshot mode.
After fixing the firing angle
and the idle speed adjuster position, i. e. after the actual start of the
test and before deactivating an injector, the engine runs at approx.
1200 rpm.
The oxygen sensor control functions
normally. The test should only be started if the radiator fan is not running
(otherwise the engine speed may be approx. 100 rpm lower).
Once an injector is deactivated,
the engine speed sinks by approx. 200 rpm. If the radiator fan starts
running during the deactivation phase, this may lead to a further decrease of
the engine speed of approx. 100 rpm.
In this test phase, uncombusted
oyxgen from the deactivated cylinder gains access to the exhaust pipe. This
means that the oxygen sensor for the relevant cylinder bank reports a lean
condition and therefore that the oxygen sensor for the relevant cylinder
bank:
oxygen sensor bank 1: cylinder
1, 3, 5
oxygen sensor bank 2: cylinder
2, 4, 6
constantly displays a voltage
lower than 100 mV.
The integrator, on the other
hand, operates at a correspondingly higher rate (greater than
128 steps), as the system attempts to enrichen the mixture.
The above described check should
be performed consecutively for each cylinder. They should all indicate the
same response, i. e. the engine speed should sink by the same amount for each
cylinder.
The purpose of this check is not
to test the function of the injectors, but is intended as a check of the
mechanism / tightness / compression of each individual cylinder.
When this test is completed, the
engine may stall. This may especially be the case if the radiator fan is
running or other consumers are switched on. The snapshot data recorded by
TECH 1 is however retained.
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