"Teapot" note


Sometimes the strange behavior of a car can perplex an inexperienced motorist.


Even simple cars, studied, it would seem, far and wide, no, no, yes, they will throw a new riddle to the “lucky” newcomer! True, in fact it always turns out that the effect has long been known, described, almost patented. But we don’t have time to read books - we learn from our own “punctures”, wearying friends with conversations about mystical cases …

… you intensively chase the "Zhigulenka" breadwinner from early morning to midnight. There is no time to deal with the machine - and it works for wear and tear … It seems that I recently installed a new fuel filter, but if you strain the memory, it turns out that it has already accumulated fifteen thousand kilometers! And any gas came across - possibly “left”, of dubious origin and quality.

So roughly (with an admixture of self-criticism!) The experienced cab driver argues when the car, instead of rolling gently along the road, suddenly starts to ride. Picked up … stalled … picked up again … - Already in the eyes of passengers it is green, and on the lips - discontent: "Why, chef, are you carrying firewood ?!"

"Chef" is ashamed. Now there is no time to look for a malfunction - and he gently tidies up the gas to drive a little quieter, but without jumping. The car really calmed down, but somehow it was sluggish. The experienced understands: the motor really can not "give out" the required power. And she is looking forward to the end of the trip: “I’ll bring people, and there I’ll figure it out!”

The thing, most likely, is the “pitch”. Little gasoline enters the carburetor (this topic does not age at all!). Nevertheless, let us recall how the carburetor float chamber is arranged and what its role is in (Fig. 1).

Recall the school: one pipe (1) flows into the pool (float chamber), and water (gasoline) flows through the other (through jets 3).

What happens if it pours more than it spills out? That's right: the fuel level will increase, the carburetor, as they say, will “overflow”, the mixture will re-enrich, the power will drop, and there the engine will stop. A balance with a needle valve 5 is called on to keep an eye on the balance, unless, of course, the latter is working: how much gas goes through the nozzles into the engine, the valve will let in the same amount.

But it happens that gasoline from the float chamber sucks out the glutton-engine, and the intake through the valve is so small that the level in it drops! If you continue to drive in the previous mode (Fig. 2), then there comes a time when the fuel jets simply become bare. In the engine, which swallowed air instead of gasoline, combustion ceases: the car, having braked, bites its nose (Fig. 3, a), and swings back (Fig. 3, b) - gasoline will again fall into the jets and the motor will pick up sharply … to again stall. All this time, gasoline somehow oozes into the float chamber - and the car can ride for a long time. As a rule, these "exercises" are stopped by the driver himself, realizing that jumping the equipment is not good: so do not break the transmission for long.

Due to the peculiarities of the location of the float chamber, the most inclined to ride are the Zhiguli with the Weber and Ozone carburetors. But other cars are not safe from this disaster, because its source is lowering the fuel level to a critical value, when any accidental push allows even a low-lying jet to swallow air. In addition, if you ever started the engine with the cover of the Ozone carburetor removed, you probably saw how ripples scatter across the surface of gasoline due to vibrations from a running engine. This "excitement" at a low level of gasoline again contributes to jumping.

So, our “boss” forgot to replace the fuel filter with a new one in time. And the old as the pollution increased resistance. The performance of a serviceable gasoline pump easily covers the needs of the carburetor even at maximum engine power, but … there is another factor, no less important for the "feed". This is the pressure that a working fuel pump can create at the outlet. It is about 0.3 kgf / cm2. As long as the pump is able to overcome the filter resistance, fuel will flow into the carburetor - but the weaker the more the filter is dirty. Consider that the motor has acquired a kind of power limiter. For example, it allows you to drive evenly at a speed of 90 km / h (Fig. 4), but further acceleration ends with jumps (again Fig. 2). It took someone to overtake or overcome the climb - and you added gas. The next moment - all the same jumps. It is hardly necessary to explain why in both cases the discharge of gas normalizes the operation of the engine!

Or the fuel filter is in perfect order, but the valve needle sticks in the up position. Or the gas line is clogged with dirt (ice, etc.) … But it is long - and there are enough "uncomfortable" places in it. But that is not all! If for some reason the tank has ceased to be ventilated (that is, air does not enter instead of the spent fuel), then with growth inside the vacuum, the pump will “suck out” gasoline more and more weakly until the tank hesitates under atmospheric pressure and the engine does not stop at all.

In winter, water can freeze in the ventilation line (in the Zhiguli it is almost programmed, since the ventilation pipe is in the form of a loop. In addition, it can be wrinkled, “broken”, etc.).

The fact that the filter was the culprit of such "adventures" can be seen in a simple way. If a strong man cannot blow the filter with his own lungs, then it’s time for the filter to landfill. The maximum pressure available to the lungs of an average person is also about 0.3 kgf / cm2! Knowing this, you can easily check the resistance of other lines, including tank ventilation.

And what will happen if all these lines are in order, but the gas pump is faulty? In general, the same thing. It’s not so important why channel number one is not able to feed number two! You will again receive a power limiter: a moderate driving pace is possible, a sports one is not. The only difference is that when the fuel pump is “weak”, sometimes a very small additional resistance is enough to disrupt the supply.

Once, a novice motorist excitedly told "about a miracle": it was worth installing a fuel filter in the highway - a new, clean one - and the car refused to go. And without a filter, I was driving … When, after a short investigation, we opened the gas pump, we did not find any obvious defects in it. "Just" the diaphragms were from time to time worn in places of contact with plastic washers. However, after installing new apertures, the car rushed like a mustang.

Fig. 1. The scheme of the float chamber: 1 - needle valve; 2 - fuel level; 3 - main fuel jet; 4 - a float; 5 - needle; 6 - case; 7 - a cover.

Fig. 2. The flow of gasoline into the float chamber is less than its consumption through the main jets: the level unacceptably falls.