Purge system with leak test function - GF47.30-P-3016BK
MODELS 219 with ENGINE 113.967 with CODE (494) USA version
MODELS 164.1 with ENGINE 113.964 with CODE (494) USA version
MODELS 251 with ENGINE 113.971 with CODE (494) USA version
Shows model 219
The legislator requires that no fuel vapors reaches the open air. The leak test must detect leaks of more than about 0.5 mm in diameter in the fuel evaporation control system. The test is performed in three stages (function chain):
- Test for major leaks
- Test for a minor leak (equal to or greater than 1 mm)
- Test for fine leak (equal to or greater than 0.5 mm).
Test for major leaks
The activated charcoal canister shut-off valve is closed and the purge control valve opened. Intake manifold vacuum present in fuel tank.
This vacuum is measured by the tank pressure sensor.
If there is no vacuum build-up in the fuel tank (around - 6 mbar within about 12 seconds), there is a major leak (e.g. filler cap open, loose hose line).
The test is aborted and the faults for the function chain and gross leak are stored.
If the motor electronics control unit detects a system with a substantial major leak, the fuel reserve warning lamp in the instrument cluster blinks and the message "CHECK GAS CAP" appears in the multifunction display.
Test for a minor leak
The purge control valve is closed at a vacuum of around -6 mbar. The system is then closed air-tight. The vacuum is them measured for approx. 30 seconds. It must not drop any faster than 0.3 to 0.5 mbar per second (depending on the level of fuel in the tank). If the vacuum drops more rapidly, there is a fine leak.
The faults for function chain and minor leak are stored.
Check for micro leakage
If no minor leak has been detected, the purge system is briefly enabled and a vacuum of approx. -6 mbar is built up again. The vacuum must not drop any faster than 0.1 to 0.15 mbar per second for a closed system (depending on the level of fuel in the tank). If the vacuum reduces more rapidly, the faults for function chain and micro leak are stored.
The reduction in the vacuum depends on the fill level in the fuel tank and on the degassing of the fuel. The degassing of the fuel is measured for a short time prior to the test and is allowed for in the fault statement.
The activated charcoal canister shutoff valve is reopened after the tests.
Test requirements
- Engine at idle speed
- Vehicle stationary
- Blocking time after starting the engine has lapsed (around 16 Minute) or mixture adaptation has been performed
- Lambda control enabled
- Intake air temperature less than +45°C
- Coolant temperature at engine start less than +100°C
- Engine load less than 35 %, transmission in drive stage D or R
- Air injection not active
- Air pressure more than around 780 hPa (i.e. no test is performed above a height of around 2500 m)
- Low loading of activated charcoal canister
- Fuel level in fuel reservoir between approx. 1/4 and 3/4 (CAN message from instrument cluster)
- If the fuel in the fuel tank is swilling around excessively (impermissible pressure leaps), this is detected by the tank pressure sensor and the check is aborted
- No fault in the activated charcoal canister shut-off valve
- No fault in the fuel tank pressure sensor
- - no fault in purge control valve (open/close)
- - battery voltage higher than 11 V
The test for minor and micro leaks is aborted if an excessive lean correction of the lambda control takes place during the build-up of the vacuum.
The function of the purge control valve is checked at the same time by the activation. If the valve sticks when closed, a gross leak fault is stored.
If no leak for the fault major leak is found (there is a clear hissing noise if there is a leak of more than 3 mm), replace fuel tank pressure sensor. The fuel tank pressure sensor may have a fault which results in a signal which is constant but still plausible (sensor sticking).
In the case of an implausible fill level resulting from a faulty fuel level sensor, the tests are not inhibited.
| Part description of tank pressure sensor | GF47.30-P-2100BK | ||
| Activated charcoal canister shutoff valve - Description of components | GF47.31-P-2100BK | ||
| Component description for the purge control valve | GF47.30-P-2020BK | ||
| Component description for the fuel level sensor | GF47.10-P-2010BK | ||
| Component description for the ME-SFI [ME] control unit | GF07.61-P-6000BK | ||
| Component description for the fuel tank | Model 219 | GF47.10-P-2000BK | |
| Models 164.1, 251 | GF47.10-P-2000BM | ||
| Component description for the activated charcoal canister | GF47.30-P-2010BK |