- A vent hose is attached to the fuel tank filler neck, which is attached to the top of the fuel level sensor in the tank. Air is vented through this hose when fuel is added to the tank.
- A thin ventilation hose leads the resulting vapors to the activated charcoal container.
- While driving, air enters through this hose when the fuel level decreases, which prevents the formation of a vacuum in the tank. Therefore, when installing the tank, pay special attention to ensure that the hose is not twisted or pinched.
The figure shows the important elements of a closed EVAP system. At a certain coolant temperature and engine load, the diaphragm valve opens (1), to which reduced pressure is transferred from the intake manifold, and a vacuum is also created in the membrane valve (2). As a result, those gathered in containers with activated charcoal (drawing on the right) fuel vapors are sucked out through the intake manifold into the combustion chambers. The activated charcoal tank is on the right fender.
Activated carbon container
To protect the environment, the tank vent hose on Renault 19 models with a petrol engine and variable catalytic converter is connected to a container containing activated carbon. This container is located behind the mudguard in the right fender. When the engine is not running or idling, gasoline vapors accumulate in this container, so that they can then enter the engine combustion chamber when the engine load increases or the speed increases. A solenoid valve is responsible for supplying fuel vapor to the working mixture, which receives a command from the injection and ignition control device. When the engine is under load, this valve opens a low pressure hose to the intake manifold or engine ventilation system, whereby fuel vapors are pumped out of the activated charcoal tank.
Checking the ventilation system
1. Raise the rear of the machine.
2. Disconnect the tank and lower it.
3. Look at how worn the hoses are and check the correctness of the individual connections and replace if necessary.
4. Disconnect the vent hose from the tank.
5. Blow out this hose with a car pump.
6. If purging is difficult, check if the hose is clogged, if necessary, replace the solenoid valve.
Safety valve
If the Renault 19 rolls over, no more than 30 g of fuel per minute can flow out of the vent line. A safety valve is located next to the filler neck of the tank in the right wing.
This valve is connected through the filler vent hose to the tank. The safety valve is positioned in such a way that even with a very strong inclination, the outlet remains closed. Also, a valve is inserted into the filler neck of the tank, which protects against overflow. If the tank overflows, the overflow safety valve opens and diverts excess pressure through the vent hose into the activated charcoal container.
Checking the safety valve
1. Raise the rear of the vehicle.
2. Unscrew the tank mount and remove it.
3. Disconnect the vent hose from the tank.
4. If you blow into this hose while the car is horizontal, the air should flow easily.
5. Otherwise, check if the hoses are clogged somewhere, replace the valve if necessary.