What is the reason? Let's start with the fuel tank. It is hidden in the passenger compartment, under the back seat. And to the right, under plastic cover, the components of the system for trapping fuel vapors are a separator and valves. Therefore, take out the back seat, remove the protective cover of the tank and the plastic upholstery.
Having seen the whole broom from tubes and hoses, do not be embarrassed! Based on the diagram given in each decent repair manual, you will quickly figure out their functions. Let's start with the "beginning" of the system - the filler neck. The plug should fit snugly against the seal. If, while unscrewing it, you don’t hear hissing, then most likely the contents of the tank communicated with the atmosphere - often because the filler neck was slightly recessed. This plug is enough to abut the edge against the body - it will not succeed in wrapping it all the way into the seal.
How to fix it? Weaken the lower clamp on the filler pipe (photo 1) and, lifting it all the way, tighten the clamp again. The first issue is fixed.
Next: negligence when refueling often leads to the fact that gasoline, splashed onto the body near the neck, penetrates the pipe into the passenger compartment, despite the gasket. We will protect ourselves - we lubricate the seal with a gas-tight sealant. When buying a sealant, carefully study the annotation - there are many oil-resistant compounds that are powerless against gasoline. The seller, pushing for the "universality" of the drug, is often disingenuous.
There are cars that cannot be doused during refueling and the most accurate one. Usually this is due to the fact that the air hose of the filler neck is pinched (photo 2): for example, it is too long and, having bent, “folded”. When refueling, it is necessary to dose gasoline in a thin stream. On the five-door Niva this hose is even longer (photo 2) and it is possible that it will be laid unsuccessfully during assembly.
Before installing the hoses (now without unnecessary bends and contractions), we will lubricate the mating surfaces with a gas-resistant sealant. We replace the regular tape clamps with worm ones so that they do not cut the hose.
Now (photo 3) you can refuel quickly and without loss. If the cabin smells like “plugging” after refueling, it is useful to check the seal of the junction of the fuel pump with the tank (photo 4). If the gasket, swelling, breaks out from under the flange and the tightening of the nuts does not help, it is better to replace it. Lubricate the new one before installation with the same sealant.
And now - to the system for trapping fuel vapors. Its malfunctions have their own specifics - they must be sought immediately after the engine stops, until the pairs
disappeared. Inspect, feel, sniff connections! The most insidious are hoses with a textile braid that hides rubber damage (photo 5). Let’s check if two thin tubes are correctly laid, through which gasoline vapors come from the tank to the separator. If it is pinched, then the pressure in the tank increases greatly and when the plug is opened, gasoline may splash out. Is the separator intact? For inspection, remove it - very carefully so as not to break the thin plastic fittings at the bottom of the tank. Usually here it is damaged - traces of gasoline leakage will indicate this. It is better to replace an untight separator - not everyone will be able to repair well.