For a long time the fuel tank had lead a life pretty much in seclusion. In Japan, in the early 1960s, the call was for cars with a greater environmental compatibility. The resulting demands from the USA (California), also reached Europe. At some point the fuel tank also had to be taken into consideration. At the latest, with the event of OBD 2, the legal demands started to take form, not only should the system be sealed from the environment, but also that this should be tested.

Basically, there can be two reasons for a leaky fuel tank. When filling up, one may have forgotten to close the filler-cap properly, or it may be losing gases, or even fuel in its liquid form through leakage. Europe by the way, has detached itself in favour of the EOBD (European On Board Diagnostics), where through electric contact, only the presence of the filler-cap is checked.

Later on in America, they had ambitions of not only recognising holes as small as 1 millimetre, but even those which were half that size. Pretty insane for a continent, where from the Arctic to the Salt Lakes, almost every temperature is represented. At least one could choose whether the defects were to be determined when the car was being driven or when it was stationary. When being driven, it is easier to build up pressure, one must however, take a certain amount of efflux into consideration. When the vehicle is stationary, the measuring is easier but the pressure must additionally be built up.

We'll probably have to get used to the fact, that also European cars make ticking- or other noises, even long after the car has been locked up and left. Speaking of ticking noises, they can also be caused by the new generation of breather- or regeneration valves. There has long been no uniform strategy to relieve the active-charcoal-filter when the saturation limit has been reached. This can be done when idling, indeed, then one must - because of the small amounts - switch to high frequency. If this is done at a certain amount of partial load, the purge-valves (see above picture) can be switched more slowly.

With the latter, money can be saved, however, with our cars always becoming quieter, they can be distinctly louder. Thus, one must pay attention to the mounting, this of course, is also valid for the workshop which replaces such a component. At least one does have the guarantee, that through the higher frequency, also in an engine which has been run at idling speed for a very long time, the active-charcoal-filter will be regenerated and on the other hand, the constant over-supply of fuel in the mixture can be compensated by the Lambda-regulation. 07/15