GF47.30-P-3016MOS Purge System With Leak Test Function
GF47.30-P-3016MOS Purge System With Leak Test Function
- MODEL 216.376, 221.176 with ENGINE 275.953 as of Model Year 09 /AEJ 08
- with CODE (494) USA version
- MODEL 216.379, 221.179 with ENGINE 275.982 as of Model Year 09 /AEJ 08
- with CODE (494) USA version
Schematic diagram of fuel tank aeration and ventilation
1 Activated charcoal canister chamber 1
2 Activated charcoal canister chamber 2
3 Activated charcoal canister chamber 3
45 Fuel filler neck
45/1 Refueling ventilation
45/2 Float with flap
58 Fluid reservoir
75 Fuel tank
75/1 Safety valve (rollover valve)
75/2 Fuel retention valve
77 Activated charcoal canister
B4/3 Fuel tank pressure sensor
Y58/1 Purge control valve
Y58/4 Activated charcoal filter shutoff valve
A Air admission line and vent line
B Purge line
Function requirements for system purging with leak test
- Engine at idle
- Vehicle stationary
- Gear range "D" or "R"
- Blocking time after engine start elapsed (approx. 16 minutes) or self-adjustment of the mixture formation occurs
- Lambda control enabled
- Intake air temperature less than 45°C
- Coolant temperature for engine start less than 100°C
- Air injection not active Air pressure greater than 780 hPa (which means that no test takes place above an altitude of about 2500 meters)
- Low loading of activated charcoal canister
- Fuel level in the fuel tank between approximately 1/4 and 3/4
- No fault at activated charcoal filter shutoff valve (Y58/4)
- No fault on the fuel level sensor, LH or RH tank half (B4/1, B4/2)
- No fault in the purge switchover valve (Y58/1)
- Battery voltage greater than 11 V
Purge system with leak test, general points
The legislator requires that no fuel vapors reaches the open air.
The leak test for the fuel evaporation control system must take place in three stages (function chain) and recognizes the following leak:
- Gross leak (leak the same or greater than a 3 mm dia.)
- Fine leak (leak the same or greater than a 1 mm dia.)
- Very fine leak (leak the same or greater than a 0.5 mm dia.)
Purge system with leak test function sequence
The function sequence is subdivided into the following steps:
- Gross leak check function sequence
- Fine leak check function sequence
- Very fine leak check function sequence
Purge system with leak test function sequence
The function sequence is subdivided into the following steps:
- Gross leak check function sequence
- Fine leak check function sequence
- Very fine leak check function sequence
Gross leak check function sequence
The activated charcoal canister shutoff valve is closed and the purge control valve opened. Intake manifold vacuum present in fuel tank.
As result, a vacuum forms in the fuel tank, which is detected by the fuel tank pressure sensor (B4/3).
If there is no vacuum buildup in the fuel tank (approx. -6 mbar within approx. 12 seconds) there is a major leak (e.g. tank cap open, hose line loose)
The test will be interrupted and the error "major leak" stored in the fault memory.
If the ME-SFI [ME] control unit (N3/10) detects a system with a substantial major leak, the fuel reserve warning lamp (A1e4) in the instrument cluster (A1) blinks and the message "CHECK FILLER CAP" appears in the multifunction display (A1p13).
If no leak for the fault major leak is found (there is a clear hissing noise if there is a leak of more than a 3 mm dia), replace fuel tank pressure sensor. The fuel tank pressure sensor may be so faulty that the signal is constant but plausible (sensor sticking).
Fine leak check function sequence
A vacuum of about -6 mbar is built up and the system is closed airproof. The vacuum is them measured for approx. 30 seconds. The vacuum must not reduce more rapidly than 0.3 to 0.5 mbar per second (depends on fuel level). If the vacuum drops more rapidly, there is a minor leak.
The test will be interrupted and the error "fine leak" is stored.
Very fine leak check function sequence
If no minor leak has been detected, the purge system is briefly enabled and a vacuum of approx. -6 mbar is built up again. In a closed system, the vacuum must not drop faster than 0.10 to 0.15 mbar per second (depending on fuel level).
If the vacuum builds up more rapidly, the "micro leak" fault is stored.
The reduction in vacuum depends on the fuel level in the fuel tank and on degassing of the fuel. The degassing of the fuel is measured for a short time prior to the test by the fuel tank pressure sensor and is allowed for in the fault statement.
The activated charcoal canister shutoff valve is reopened after the tests.
The test for minor and micro leaks is aborted if an excessive lean correction of the lambda control takes place during the buildup of the vacuum.
The function of the purge control valve is checked at the same time by the activation. If the closed switchover valve jams, the "major leak" fault is stored.
