17C-8
MR-372-J84-17C000$059.mif
V2
GAS INJECTION
Fault finding - Introduction
LPG 3000
Program No: AB
Vdiag No: 08/10
17C
ROAD TEST (in Petrol mode, then in LPG mode)
–check that the stabilisation time is normal,
–check that the engine does not stall under sudden braking and that it maintains a stable idle speed until the vehicle
comes to a stop,
–put the vehicle in 4th gear, at a steady speed of 36 mph (60 km/h). Check that the vehicle accelerates
progressively under full load acceleration.
Maintenance operations:
–no adjustment,
–removal of internal components is not permitted,
–if LPG clips are removed, they must be replaced,
–if LPG unions are removed, they must be replaced.
The tank must be bled before removing:
●the fuel tank,
●a component bolted to the fuel tank,
To remove the following, bleed all gas contained in the gas circuit (except the gas in the tank):
●the filler neck,
●the pipes,
●the filter,
●the pressure relief valve,
●the solenoid valve. IMPORTANT
Before performing any work on the vehicle, drain the LPG circuit.
Only personnel who have undergone special LPG training can work with gas unions where gas is circulating and
which run from the expansion valve via the fuel tank.
Equally, only these persons are permitted to perform servicing and repair operations on LPG vehicles.
Workshops can only carry out work on the fuel tank if they have a degassing burner. If the tank cannot be
degassed, do not carry out any work and contact the Comité Français du Butane et du Propane (French
Butane and Propane Commission) by fax on 01 41 97 02 89.
17C-9
MR-372-J84-17C000$118.mif
V2
17C
GAS INJECTION
Fault finding - System operation
1. System operation:
Composition
–The LPG injection system consists of the:
–LPG tank,
–fuel sender,
–overpressure unit (thermally triggered),
–LPG solenoid valve relay,
–tank solenoid valve,
–reducer (LPG) or expansion valve (CNG),
–expansion valve,
–filling spigot or socket,
–LPG hose,
–tank pressure sensor,
–LPG pipes,
–unions,
–airtight cover,
–regulator valve or anti-return valve,
–excess pressure valve,
–LPG filter,
–temperature and pressure sensor,
–LPG computer,
–LPG expansion solenoid valve,
–gas injectors,
–LPG or petrol selection switch,
–fuel sender relay,
–LPG tank relay,
–fuel pump cut-off relay.
Operating principle
The GAS 3000 computer electronically manages the operation of the LPG systems (Liquefied Petroleum Gas) and
CNG (Compressed Natural Gas).
The engine must be started in Petrol mode. The vehicle will automatically switch to "Gas" mode after starting if the
"gas" configuration was selected beforehand. "Petrol" mode switches to "gas" mode after a certain time delay, which
depends on the engine coolant temperature.
Petrol mode operates autonomously. Information is shared between the Petrol computer and the LPG computer via
a CAN connection.
The K line shared by the two computers allows diagnostics to be run on both the petrol and the LPG systems.
The Petrol computer is also the supervisor of the LPG system and includes, in addition to petrol-specific functions,
functions for adapting engine management programming to LPG operation.
Therefore, the Petrol computer includes settings and variables that are specific for LPG operation, e.g. ignition
advance adjustment in LPG mode, LPG flow rate setting, richness regulation, engine operating mode, etc.
It controls the choice of program (petrol start-up etc.) and controls the transition phases for switching from one
operating mode to the other: Petrol → Gas or Gas → Petrol. The fuel pump is regularly supplied to keep the system
under pressure in the event of a possible return to "Petrol" mode (if the "Gas" tank is detected as empty or if a fault
is detected).
LPG 3000
Program No: AB
Vdiag No: 08/10
MR-372-J84-17C000$118.mif
17C-10
MR-372-J84-17C000$118.mif
V2
GAS INJECTION
Fault finding - System operation
LPG 3000
Program No: AB
Vdiag No: 08/10
17C
The GAS 3000 computer manages "gas" actuator control, i.e. the "gas" injectors, the gas system relays and solenoid
valves, the fuel pump cut-off relay and the management of the fuel sender. Before switching to "Gas" mode, the
computer always checks that the pressure and the temperature of the gas are correct and that the "gas" solenoid
valves are open.
The combustible material is stored in an independent toric tank. LPG is stored in a semi-gaseous state at a pressure
of approximately 15 bar.
CNG is stored in a cylindrical tank in a gaseous state at a pressure of approximately 200 bar, and is transported to
the expansion valve/reducer via a rigid high pressure pipe. The rest of the system is a low pressure pipe going from
the expansion valve/reducer to the injectors. For CNG, there is a gas filter between the expansion valve and the rail.
Malfunctions / Special cases
These are characterised by operation in Petrol mode, although the driver has selected LPG mode.
An operational fault must be caused by the LPG system if it cannot be reproduced in Petrol mode.
Forced Petrol mode when LPG is faulty.
The level 1 warning light is controlled by the petrol injection computer; the gas warning light is controlled by the GAS
3000 computer.
The system automatically switches to "petrol" mode when the tank is empty or when the conditions allowing
operation in "gas" mode are not satisfied.
