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Diagnose
Status September 2003 (EvoBus-Service / AFT)
Page: 73 of 83
4.3.4
Temporarily switch off engine run-on
The M 447 hLAG is switched off with the so-called "Engine run-on" . This means that when Ter. 15 is
switched off, the high and low-pressure cut-off valve are switched off (gas supply switched off), however
the gas injection and ignition continue to run so that the engine continues running until the gas in the low-
pressure line is consumed (to protect the catalyst) and the engine dies due to a shortage of gas. After the
gas in the low-pressure line is used up, the pressure in the injector block drops to approx. 1 to 2 bar.
When the following Customer Service routine activated: "Temporarily switch off engine run-on", the gas
injection is immediately stopped and the gas cut-off valves are closed after Ter. 15 is switched off. If the
gas injectors are "tight", then the gas pressure in the injector block is approx. 8 bar. A leak test of the gas
injectors can be carried out in this way.
Notes:
-
The engine run-on can be switched off once by starting the routine "Switch off engine run-on"
(repeatable!)
-
Deactivation of the function with Ter. 15 off and control unit run-on ended!
4.3.5
Manual compression test
The Customer Service routine: "Manual compression test" is an auxiliary function when conducting a
manual compression measurement. This routine can be activated with
Star-Diagnosis
.
The activation of this Customer Service routine results in:
-
the gas injection being switched off by
– the gas mass being set to zero and no actuation of the gas injectors being carried out,
– the gas cut-off valves being switched off (closed)
-
the actuation of the ignition being switched off
-
the throttle valve being opened (throttle valve position = 80 °DK)
Notes:
-
This Customer Service routine can only be deactivated by switching off Ter. 15
-
The function the only be activated when
– the throttle-valve reverence movement has failed
– a short-circuit to earth of the gas injectors is detected
– the engine dwells in the "Starting" or "Normal" state