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G424F(FE) Service Manual
Chapter 5. Engine Management System (EMS)
134
Other system features include:
Tamper-Resistance
Special tools, equipment, knowledge, and
authorization are required to effect any changes to
the MI-07 system, thereby preventing unauthorized
personnel from making adjustments that will affect
performance or emissions.
Diagnostics
MI-07 is capable of monitoring and diagnosing
problems and faults within the system. These
include all sensor input hardware, control output
hardware, and control functions such as closed-loop
fuel control limits and adaptive learn limits. Upon
detecting a fault condition, the system notifies the
operator by illuminating the MIL and activating the
appropriate fault action. The action required by each
fault shall be programmable by the OEM customer
at the time the engine is calibrated.
Diagnostic information can be communicated
through both the service tool interface and the MIL
lamp. With the MIL lamp, it is possible to generate a
string of flashing codes that correspond to the fault
type. These diagnostics are generated only when
the engine is not running and the operator initiates a
diagnostic request sequence such as repeated
actuations of the pedal within a short period of time
following reset.
Limp Home Mode
The system is capable of "limp-home" mode in the
event of particular faults or failures in the system. In
limp-home mode the engine speed is approximately
1000 rpm at no load. A variety of fault conditions can
initiate limp-home mode. These fault conditions and
resulting actions are determined during calibration
and are OEM customer specific.
Service Tool
A scan tool/monitoring device is available to monitor
system operation and assist in diagnosis of system
faults This device monitors all sensor inputs, control
outputs, and diagnostic functions in sufficient detail
through a single access point to the SECM to allow
a qualified service technician to maintain the system.
This Mototune software (licensed by Mototron
Communication) is secure and requires a crypt-
token USB device to allow access to information.
LPG Fuel System Operation
The principles outlined below describe the operation
of MI-07 on an LPG fuel system.
An LPG fuel system consists of the following
components:
• Fuel filter
• Electric fuel lock-off solenoid valve
• Fuel pressure regulator/vaporizer
• Two orificed fuel trim valves
• Gas/Air mixer with fixed orifice for trim system and
fuel temperature sensor
• Miscellaneous customer-supplied hoses and
fittings
Fuel is stored in the customer-supplied LPG tank in
saturated liquid phase and enters the fuel system
from the tank as a liquid and at tank pressure. Fuel
passes through a high-pressure fuel filter and lock-
off solenoid, and is then vaporized and regulated
down to the appropriate pressure to supply the
mixer. The regulator controls the fuel pressure to the
gas/air mixer.
Dual Dither Valve
The key to meeting emissions requirements when
operating in LPG is the dual dither valve hardware in
the fuel system. Similar to the MI-04 system, the
dual dither system modulates the fuel pressure
regulator outlet pressure by providing an offset to
the regulator secondary stage reference pressure.
By adding a second dither valve, or fuel trim valve
(FTV), to the MI-07 system, smoother, more
accurate control of supply pressure is achieved,
resulting in better control of air fuel ratio and
emissions. This smoother control also minimizes
wear on fuel system components such as the
regulator diaphragm and lever by significantly
reducing the pressure pulsations observed with a
single FTV.
Regulator Pressure Offset
Regulator pressure offset is achieved through the
use of a fixed orifice and a variable orifice in series.
The inlet to the fixed orifice is connected to the
mixer inlet pressure (roughly equal to ambient
pressure). The outlet of the fixed orifice is connected
to both the pressure regulator reference port and the
inlet to the two FTVs (the variable orifice) that act in
parallel. The outlets of the FTVs are connected to
the mixer outlet, referred to as Air Valve Vacuum
(AVV). Thus, by modulating the FTVs, the pressure
regulator reference pressure can be varied between
mixer inlet pressure and AVV. For a given change in
the pressure regulator reference pressure, the
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Страница 31: ...G424F FE Service Manual Chapter 2 Recommended Maintenance 29 ...
Страница 36: ...G424F FE Service Manual Chapter 3 Engine Mechanical System 34 MAIN BEARINGS 0 50 UNDERSIZE ...
Страница 86: ...G424F FE Service Manual Chapter 3 Engine Mechanical System 84 ...
Страница 113: ...G424F FE Service Manual Chapter 4 Engine Electrical System 111 2 Alternator and outer terminal connection inspection ...
Страница 153: ...G424F FE Service Manual Chapter 5 Engine Management System EMS 151 Figure 22 SECM Wiring Diagram for G424FE LP System ...
Страница 162: ...G424F FE Service Manual Chapter 5 Engine Management System EMS 160 SECM Wiring Diagrams for G424F LP Engine ...
Страница 230: ...G424F FE Service Manual 228 Chapter 8 Basic Troubleshooting Irregular Idling Or Engine Is Suddenly Stopped ...
Страница 231: ...G424F FE Service Manual 229 Chapter 8 Basic Troubleshooting Engine Hesitation Or Insuffient Accelelation ...
Страница 232: ...G424F FE Service Manual 230 Chapter 8 Basic Troubleshooting ...
Страница 234: ...G424F FE Service Manual 232 Chapter 8 Basic Troubleshooting ...