Purge system with leak test function - GF47.30-P-3016AM
MODEL 211, 219 with ENGINE 113.990 with CODE (494) USA version
MODEL 215, 220 with ENGINE 113.991 with CODE (494) USA version
MODEL 230 with ENGINE 113.992 /995 with CODE (494) USA version up to Model Year 2008
MODEL 463 up to 31.5.12 with ENGINE 113.993 with CODE (491) USA version
Models 211, 219
Models 215, 220, 230, 463
The US legislature requires that the fuel vapors are not released into the atmosphere.
The leak test for the fuel evaporation control system must detect leaks with a diameter of over 0.5 mm and must take place in three stages (function chain):
- 1. Test for a major leak (equal to or greater than 3 mm)
- 2. Test for a fine leak (equal to or greater than 1 mm)
- 3. Test for a very fine leak (equal to or greater than 0.5 mm)
- Test for a major leak
The activated charcoal canister shut-off valve (Y58/4) is closed and the purge control valve (Y58/1) opened. The vacuum in the intake manifold reaches the fuel tank (75).
As result, a vacuum builds up in the fuel tank, which is detected by the fuel tank pressure sensor (B4/3).
If there is no vacuum build-up 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 gross leak registered in the fault memory.
The fuel reserve warning lamp (A1e4) also flashes in the instrument cluster (A1) for the fault gross leak and the "CHECK FILLER CAP" appears in the multifunction display (A1p13).
- Test for a fine leak
The purge control valve is closed at a vacuum of around -6 mbar. The system is closed and thereby 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 registered in the fault memory.
- Test for a very fine leak
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 drops more rapidly, the fault "very fine leak" is registered in the fault memory.
The activated charcoal canister shutoff valve is reopened after the tests.
Test requirements
- Engine at idle speed
- Vehicle stationary
- Drive position "D" or "R" is engaged
- Blocking time after engine start elapsed (approx. 16 minutes) or mixture adaptation occurring
- Lambda control enabled
- Suction / charge air temperature less than 45°C
- Coolant temperature for engine start < 100°C
- Air injection not active
- Air pressure >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 in the activated charcoal canister shutoff valve
- No fault in the fuel tank pressure sensor
- No fault in the purge control valve
- Battery voltage > 11 V
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 by the fuel tank pressure sensor and is allowed for in the fault statement.
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 closed switchover valve jams, the major 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).
| ME-SFI control unit - location/task/design/function | GF07.61-P-5000AM | ||
| Fuel tank - location/design/function | Models 211, 219 | GF47.10-P-3000TK | |
| Models 215, 220 | GF47.10-P-3000KM | ||
| Model 230 | GF47.10-P-3000RM | ||
| Model 463 | GF47.10-P-3000GM | ||
| Activated charcoal canister - location/task/design/function | GF47.30-P-3102AM | ||
| Purge control switchover valve - location/task/design/function | GF47.30-P-4030AM | ||
| Fuel tank pressure sensor - location/task/function | GF47.30-P-4032AM | ||
| Activated charcoal canister shutoff valve - location/task/design/function | GF47.30-P-4033AM |