Why isn't fuel getting into the carburetor? Main causes and methods of troubleshooting

Causes

Fuel does not enter the carburetor for several reasons

:

• lack of pressure in the fuel supply system;
• the fuel pump has failed (quite a common problem);
• problems with the vacuum pipeline;
• dirt plug in the supply hose from the gas tank;
• production of a gas filter;
• other;

The engine may not start not only because there is no fuel supply to the carburetor, although this is the first thing that comes to mind. The engine does not respond to ignition due to:

• lack of current supply to the coil;
• no high voltage from the coil;
• high voltage does not reach the spark plugs;
• there is fuel in the carburetor, but it does not reach the chambers;
• failure in the ignition system, etc.

How to understand that the cause of engine interruptions is the fuel pump

Diagnosing problems with the fuel pump in a car with an injection engine is much easier than in a car with a carburetor engine. The fact is that when you turn on the ignition, you can clearly hear the sound of the electric motor of the fuel module. It lasts for several seconds. This sound indicates that the fuel pump is turning and pumping fuel.

If this happens when you turn the key, then there is nothing wrong with the device itself, and the cause needs to be looked for elsewhere. Well, if when you turn on the ignition you do not hear the characteristic sound of the pump, you can be sure that the problem is in it, or in the elements of its energy supply.

Checking the fuel supply

The simplest, but far from effective way to determine whether fuel is supplied to the carburetor is to check it manually. To do this, the inlet fitting on the carburetor is released from the fuel supply hose. Press the lever for manual pumping of gasoline several times - if fuel comes out from the removed hose, then the problem is stuck in the carburetor; if it doesn’t work, you need to contact the fuel pump.

However, manual checking is not effective

, because, firstly, it depends on the position of the damper in the air filter, and secondly, there are often situations when in manual mode everything is fine, but we start the engine - there was no fuel in the carburetor, and there is no fuel.
Testing with a bottle in this regard is a more reliable method of testing gasoline supply. To do this check, tie a plastic bottle to the removed gasoline supply hose and start the engine. This verification method gives an unambiguous answer about the location of the fault.

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Start with the relay and fuse

Considering that the fuel supply module is located in the car tank, and it is not so easy to get to it, it is better to start diagnostics with the relay and fuse:

1. Unscrew the screws securing the cover of the mounting block located to the left of the steering column.
2. Underneath it, find fuse F3 (15 A) and relay R2. These are the elements that we need to check.
3. As for the fuse, it needs to be “ringed” with a tester. If unusable, replace it.

Checking the relay in a garage is quite difficult. But you can take a similar one (from an adjacent socket), a known good relay, and install it instead of the one being diagnosed. Now turn on the ignition. Is the fuel pump pumping? The reason has been found! Well, if nothing has changed, move on.

Carburetor malfunction

The first to be inspected is the fine-mesh filter after the inlet fitting. It is designed to clean the fuel mixture before entering the float chamber. It closes with a plug that needs to be unscrewed, the filter mesh removed, washed and blown out, then put back in place and screwed on the cap.

There is no point in checking the jets, since if one were clogged, the engine would operate, albeit in a different mode.

Why doesn't fuel enter the car's cylinders?

To find out why fuel is not getting into your car's cylinders, read some of the test methods below.

There are differences in testing carburetor engines and engines with injection. But there is also something in common.

It is advisable to fill the tank for checking by the car owner himself (10 liters of AI-93 gasoline), so as not to fall for the falsification of some gas station. Gasoline of other brands will not be suitable due to the use of knock sensors in some engines, which are triggered if low-octane gasoline is used, after which the main jet hole is blocked by the solenoid valve in the float chamber, which leads to the engine stopping.

• It often happens that a car that has been sitting with an empty or half-empty tank for more than a year does not start from the starter.

The reason for this is the evaporation of light fractions of gasoline, which ignite the mixture in the cold. The remaining fuel has already been modified into a different substance, with different properties. You can try to start the engine (both types) by manually supplying fuel. In other words, if the carburetor is empty, you need to splash a thin stream of gasoline into its neck.

For an engine with an intake, you can similarly start it through the following operation: remove the hose from the manifold or the vacuum brake booster hose and pour gasoline into the manifold.

Piping and gas tanks are also a common feature of these engines. Whole, undamaged tubes extending from the carburetor do not affect the starting and operation of the engine. But their influence is noticeable in fuel consumption, pollution or purity of exhaust gases, automatic devices of the car and engine power.

• You can determine why fuel does not enter the cylinders of the car when the engine, cold to the touch, does not start, by pouring gasoline from a small container into the carburetor and observing the flashes for a while.

First of all, through the inspection window, we will make sure that there is fuel in the float chamber. If it is not visible in the warm season, the reason may be that the chamber is overcrowded and the mixture is oversaturated. If there is no viewing window (and this happens, however, very rarely), you should open the air damper slightly and look at the flow of gasoline into the diffuser of the accelerator pump, while sharply pressing the gas.

Gasoline is not supplied, which means the fine filter may be clogged. The filter is considered disposable, it is not washed, but can be replaced with a similar domestic one.

• Almost as often, the engine refuses to work for another reason, just as common: the electric or mechanical fuel pump is faulty.

In the fuel line in front of the electric pump there may be a conical mesh microfilter. To check it, remove the hose between the fuel tank and the pump. The strainer at the carburetor inlet may be clogged with dirt. Sometimes dirt gets into the carburetor itself if its operation is disrupted due to the lack of an air filter, or due to defects in the exhaust gas recirculation valves. In this case, steam and soot are observed in the air filter housing.

• Engines with injection most often fail

Fuel pump testing

The fuel pump, like the air filter, has a manual feed lever. The first check is carried out with its help.

Since the fuel line is already disconnected from the inlet fitting on the carburetor, it can also be disconnected from the fuel pump and purged as a preventive measure. A rag is placed under the outlet fitting of the fuel pump to prevent gasoline from splashing and spreading throughout the engine and engine compartment, and the manual feed lever is pumped several times.

The presence of gasoline at the outlet fitting of the fuel pump will indicate loosening of the pump mounts

. It is necessary to tighten the mounting bolts on the pump housing.

Lack of fuel supply again leaves two options for failure

. The first option is failure of the fuel pump, which is most likely, and the second is a clogged supply line from the gas tank to the pump, which is less likely and rarely occurs.

Check the operation of the pump in the same manual mode by covering the hole in the outlet fitting with your finger and pumping the lever.
The pressure won't be strong, but it should be there. The absence of a characteristic sound of air escaping gives a definite answer about its failure. Based on the above, we can conclude that there are only two truly serious reasons for the fact that fuel does not flow into the carburetor - failure of the fuel pump and a breakdown in the carburetor itself. Other reasons, such as clogged lines or input and output filters, are less likely and less common.

No gasoline supply to car engine

Stopping the supply of gasoline to the engine is one of the main car malfunctions.

Its cause may be a malfunction of one or more elements of the power system: fuel tank, fuel lines, carburetor, filters. In such a situation, the car engine may not start at all (either cold or warm), and the engine may suddenly stop while driving.

Checking the fuel supply

A check will help narrow down the troubleshooting. You should check whether fuel is flowing from the fuel system to the carburetor or not. Remove the hose from the carburetor inlet pipe or from the fuel outlet pump and press the manual fuel pump lever on the fuel pump several times. If there are any problems with the fuel supply from the fuel lines, tank, or a faulty fuel pump, the fuel stream from the hose will be absent or too weak. If there is a jet, the carburetor is faulty.

Checking the fuel supply through the engine power supply using the manual fuel pump lever

Several of the most common reasons for the lack of fuel supply to the engine using the example of the fuel system of VAZ 2108, 2109, 21099 cars

We begin to look for a fault in it if fuel comes from the fuel pump (see check above).

What to look for in the carburetor.

— Strainer in the carburetor (for clogging).

We unscrew the filter plug, remove the filter mesh element, wash it with gasoline, clean it with a toothbrush, and blow it with compressed air. We also clean and blow out the hole under the filter in the carburetor cover.

Solex carburetor fuel strainer

— Details of the float mechanism in the float chamber of the carburetor.

The reasons for stopping the supply of fuel from the float chamber may be the needle valve needle hanging in the upper locking position, due to the needle being skewed in the body or the floats touching the walls of the float chamber (do not go down). You should also pay attention to the correct adjustment of the fuel level in the carburetor float chamber. To check the elements of the carburetor float chamber, remove its cover.

Solex carburetor needle and floats

In some cases, just a light tap on the carburetor is enough to wedge the valve needle.

— Fuel nozzle of the GDS of the 1st chamber of the carburetor, emulsion tube.

We remove the carburetor cover, turn out the tube and jet, clean them with a wooden stick or copper wire, rinse with acetone, and blow with compressed air.

Air jets, fuel jets, emulsion tubes and Solex carburetor wells

Now the reasons for stopping the fuel supply are related to the power system itself (fuel does not come out of the fuel pump)

— The gas tank has run out of fuel.

If for some reason the sensor on the instrument panel is deceiving, then it is quite possible to find yourself in a situation where the fuel in the tank has already run out, and the driver is not even aware of it. Look at the fine fuel filter. If it is empty or there is very little gasoline in it, most likely the reason for the shutdown of fuel supply is its lack of fuel.

Fuel tank (gas tank) VAZ 2108, 2109, 21099

— The fuel pump itself is faulty

There may be problems with the diaphragm (leaky), pusher, strainer or valves. A broken diaphragm will give itself away as fuel leaks at the fuel pump and the smell of gasoline. To clean the strainer, you must remove the fuel pump cover. The protrusion of the pusher should be checked and adjusted. In addition, a feature of the DAAZ fuel pumps of VAZ 2108, 2109, 21099 cars is their refusal to work in hot weather, when the engine is very hot. In such a situation, a wet rag placed on top of the fuel pump cover will help. For more information, see “Fuel pump malfunctions.”

Measuring the protrusion of the VAZ fuel pump pusher

— The fuel line from the gas tank to the fuel pump is faulty (damaged, clogged)

It is necessary to ensure the safety of both the metal pipe of the line and its rubber hoses. To do this, it is advisable to inspect it from the tank to the fuel pump. Damage to the line is usually accompanied by the smell of gasoline and drips.

You can check the fuel line for blockages by removing the fuel hose from the inlet fitting of the fuel pump and blowing into it (with your mouth or through the pump) in the direction of the gas tank. The cap on the gas tank filler neck should be removed. The bubbling of the supplied air in the gas tank indicates that the fuel line is clean. Otherwise, you need to blow it out with a compressor.

Checking the fuel pump valves

— The fine fuel filter is clogged

Replace the filter with a new one or temporarily remove it from the system by inserting a piece of tubing in its place and securing it with clamps.

Fine fuel filter

— The fuel intake in the gas tank is clogged

You can remove it on VAZ 2108, 2109, 21099 cars by lifting the rear seat through the hatch in the body. First of all, you should pay attention to the intake strainer. It must be cleaned with a toothbrush, rinsed with gasoline and blown with compressed air. It is also necessary to blow out the fuel intake itself, since dirt accumulation may be present not only in its mesh filter, but also in it itself. A clogged intake and its filter can cause not only a stop in fuel supply, but also interruptions in engine operation, both at idle and while driving.

Fuel intake in the gas tank with a strainer

The cause of contamination of the intake may be silt deposits that accumulate over time in the gas tank. To prevent such a situation, you should carry out preventive cleaning (see “Cleaning the fuel tank”).

These are, perhaps, all the main reasons for the cessation of fuel flow into the engine on VAZ 2108, 2109, 21099 vehicles.

Notes and additions

To help when troubleshooting the fuel system, its diagram for VAZ 2108, 2109, 21099 cars is useful - “Fuel system diagram for VAZ 2108, 2109, 21099 cars.”

Twokarburators VK - More information on the topic in our VKontakte group, on Facebook Twokarburators FB and on Odnoklassniki - Twokarburators OK

More articles on the fuel system of cars

— Gasoline used on VAZ 2108, 2109, 21099 cars

— Fuel consumption of VAZ 2108, 2109, 21099 cars

— Malfunctions of the fuel system of VAZ 2108, 2109, 21099 cars

— How to increase the power of a car engine without tuning?

— Checking the floats of the Solex carburetor

Clicking noises when trying to start the engine

If all contacts and fuses of the Niva are normal, you should turn the ignition key to the “start” position and listen to see if the relay clicks. If clicking sounds are heard clearly, the problem may lie in the starter voltage relay, the solenoid relay, or the starter coil circuit.

In “male” car services, the serviceability of the solenoid relay is usually checked by closing its contacts with a large screwdriver until the starter begins to rotate. For safety reasons, this should not be done under any circumstances.

If the problem is in the intermediate relay, then it is quite easy to replace it on the Niva. It is enough to insert the new relay block into the terminal block, observing the sequence and polarity of the connection.

To check the serviceability of the solenoid relay, the starter will have to be removed. After this, holding the starter, you should connect it to the battery and apply voltage to the contact of the solenoid relay. If a click is clearly heard, then the solenoid relay is working properly.

Perhaps the cause of the malfunction is oxidized and burnt contact pads of the starter. To check them, you should disassemble the solenoid relay and clean the contact group. Sometimes the solenoid relay is non-separable and must be replaced along with the contact group.

If the solenoid relay works, but the starter rotor does not rotate, it is necessary to check the condition of its brushes, which may have worn out so much that they have lost contact with the winding. In this case, repairing the starter costs little money.

If the rotor is jammed or its winding is burned out, it is best to replace the starter assembly.

Electric drive and filter

The fuel pump in the injection VAZ 2114 is an element of the fuel module, which is located in the car’s tank. It also includes:

• coarse filter;
• fuel level sensor;
• pipes for connection to the fuel line.

To get to the module, you need to remove the lower part of the rear seat, disconnect the wiring harness and unscrew the 8 screws securing its cover. Remove the entire device assembly. First of all, inspect the coarse filter. If it is clogged, replace it.

To test the electric motor, you will need to connect it directly to the battery terminals. If it is operating normally, “ring” the wiring and check the contact of the ground wire on the module cover. If the electric motor shows no signs of life, the question “why the fuel pump doesn’t pump” has finally found its solution.

It is not advisable to try to repair it yourself. Just buy a new motor and install it in place of the old one. And yet, you shouldn’t spend money on buying the entire module, which now costs about 3 thousand rubles. Buy the electric motor and a new filter separately. All this will cost you three times less.

What's the result?

As you can see, if you have certain skills and knowledge, you can determine why gasoline does not flow into the engine both on engines with a carburetor and on injection power units. However, many problems can be solved yourself. For example, it is quite possible to repair, clean and adjust a carburetor in a garage. The same can be said about cleaning injectors yourself.

Finally, I would like to note that timely replacement of fuel filters, regular cleaning of the injector or carburetor, as well as driving on good quality fuel are the key to the proper operation of the power system of a gasoline or diesel engine.

Also, driving with a half-empty tank in winter leads to the active formation of condensation, which accumulates in the gas tank. As a result, condensate (water) not only settles at the bottom and enters the combustion chamber, but also causes severe corrosion of the tank walls. As a result, rust appears in the tank, and in the case of through corrosion, active fuel leaks inevitably occur.

Diagnose faults that may indicate problems with the fuel pump. Self-check of the device, measuring the pressure in the fuel rail.

How to determine why the fuel pump does not pump or works poorly. Fuel rail pressure, pump diagnostics. Wiring, relays, fuel pump fuses.

Why is it necessary to clean the fuel pump mesh? When is it better to change and how to clean the fuel pump mesh? How to properly remove the fuel pump, subtleties and nuances.

What to do if the engine is “stupid”, does not pull, and there is a deterioration in engine response after pressing the gas pedal. Basic faults, diagnostics.

The causes of whistling and increased noise during operation of the fuel pump are overheating of the pump. How to diagnose and fix the problem yourself. Tips and tricks.

Airing of the diesel fuel system: signs of malfunction and diagnostics. How to find the location of the air leak yourself, ways to solve the problem.

Checking the starter circuit

For starter malfunctions, see the section Diagnosis of engine malfunctions: “The crankshaft does not turn with the starter”, “Lots of noise when the starter is running”

How to check the functionality of the starter circuit

If the starter does not crank the engine when the ignition key is turned to the appropriate position, then there are four possible reasons:

1. the battery is discharged;

2. electrical connections between the starting relay, battery and starter are broken, i.e. current from the battery is not supplied to the starter;

3. the starting (traction) relay is faulty;

4. The starter is stuck or its electrical part is faulty.

• To check the battery, turn on the headlights. If they go out after a few seconds, the battery is discharged or damaged. If the headlights are bright, turn on the starter and see what happens to the headlights. If the headlights dim, voltage is supplied to the starter, but it does not rotate. The starter needs to be removed for inspection. If the starter rotates very slowly, proceed to the next test.

• If the headlights still shine brightly when you turn on the starter, then there is no voltage reaching it. Check all connections from the battery to the start relay and starter for tightness and cleanliness. If the car has a good battery, then the most likely cause is a malfunction of the starter itself. Check that the flexible ground wire between the engine and the body is tightly screwed - this sometimes helps eliminate an apparent malfunction.

• If no results are achieved, turn off the headlights to avoid draining the battery. You may hear a clicking sound each time you turn the ignition key to the starter position. These are the sounds of the solenoid (traction relay) operating, but this does not mean that the main contact is operating properly. (If you do not hear a click from the relay, it may be faulty.) The solenoid contact can be checked by connecting a voltmeter or test light to the main wire connection (battery to starter) on the "starter" side of the relay and to ground. When you turn the ignition key, the voltmeter should show voltage, or the light should light up. If this does not happen, then the traction relay is faulty. (Do not connect a light bulb to the two relay contacts. If the starter is working, the light will light up.) If, in the end, it is determined that the relay is working properly, and voltage from the battery is supplied to the starter, then most likely the starter itself is faulty.

Video

Reasons why Niva 4x4 does not start (the starter does not turn)

January 28, 2022 LadaOnline 135 776 Often, owners of a VAZ 2121 or 2131 SUV encounter problems with starting the engine. For example, when you turn the ignition key, the starter does not turn. Let's look at possible problems with the Niva 4x4 starter and ways to solve them.

Where is the starter relay located?

The starter relay is located under the auxiliary fuse box next to the ignition relay. On Niva 21214, the starter activation relay is attached to the injection system relay bracket.

Niva starter circuit 2121, 2131

1 – starter; 2 – rechargeable battery; 3 – generator; 4 – starter activation relay; 5 – ignition switch

Starter activation circuit: When the starter is turned on, the voltage from the battery through the auxiliary relay (No. 4 type 113.3747-10) is supplied to the windings of the starter solenoid relay (retractor II and retaining I). After closing the contacts of this relay, the pull-in winding is turned off.

Possible malfunctions if the starter does not turn

Possible malfunction Diagnostics Solution

Have you encountered the problem of starting the engine when the starter does not turn? What was the cause of your problem? Let us remind you that other instructions for the repair and operation of Niva 4x4 can be found in this category or by content.

Keywords: Niva starter | Niva engine | Niva ignition system | Niva power system | ECM Niva

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Why does the starter turn normally, but the engine does not catch and does not start?

In half the cases when a car refuses to start, the starter is to blame. At the same time, the other half occurs in situations where the starter regularly rotates the crankshaft, but the engine starts only after repeated attempts or is completely silent. This could be due to a variety of reasons.

Driver inattention or negligence

The notorious human factor can manifest itself in the most unexpected ways. For example, a banal lack of fuel or an alarm that blocks the fuel pump. It also happens that some “well-wisher” clogged the exhaust pipe, or a careless driver, while backing up, got stuck in a pile of soil or a snowdrift. Such reasons do not fall into the category of technical malfunctions, but they can spoil a lot of nerves.

Technical problems - starter malfunctions

The starter is considered faulty in the following cases:

1. The Bendix gear cannot engage with the flywheel ring gear. This manifests itself in a loud metallic grinding sound that appears when the starter is turned on. The reason for this phenomenon is wear of the mating surfaces, chipped teeth, etc. The solution to the problem is to install a new flywheel or ring. The latter can be rotated 180° and thus avoids the need to purchase a new part.
2. The overrunning clutch or retractor relay mechanism is stuck. At the same time, the starter motor hums, but it makes no attempt to start the engine. In some cases, repeated attempts to turn on the starter help, but this only postpones the need for repair or replacement for some time.
3. The crown is loose. A similar malfunction occurred on cars from the end of the last – beginning of this century, including the popular “nines”. In this case, the starter engages with the ring and begins to turn it, but it turns on the flywheel with a grinding noise. Only replacing the latter will help.

CORRECT DISASSEMBLY AND REPLACEMENT PROCEDURE

In order to properly remove the fuel pump, you must perform the following sequence of actions:

• Buy a repair kit right away.
• Remove the air filter and its housing.
• Disconnect the gasoline supply and return hoses from the fuel pump fittings.
• Unscrew the nuts that secure it.
• Remove it carefully so as not to damage the gaskets.
• After this, inspect each part for cracks, check all its valves for leaks.
• Make sure that the discharge and suction fittings remain motionless in their sockets.
• The diaphragms must be free of peeling and ruptures.
• The filter must be absolutely clean and undamaged.
• Wash all filter parts with gasoline and then rinse with a compressor.
• Replace all damaged parts, it is also recommended to install a new pump gasket.
• When installing the gasket, apply Litol-24 type lubricant to its surface.
• If the housing is damaged or there is other irreparable damage to important parts, the pump will have to be completely replaced.
• Then you need to move on to installing the pump in place.
• In this case, you should immediately adjust its supply using spacers.
• To do this, you need to measure the protrusions of the pusher.
• If the protrusion is too strong, the gasoline pressure will be increased, which will easily break the carburetor shut-off valve.
• If the distance is lower than required, when the load increases and the vehicle speed increases, insufficient gasoline will flow into the carburetor.
• Install the gasoline pump in reverse order.
• Make sure that the arrow located on the body points towards the carburetor.
• When installing the diaphragm unit, the holes in its gasket should be located away from the muffler pipe.

Thus, you have outlined detailed instructions for removing and disassembling the fuel pump, which will help you carry out this operation yourself. You can finish here, you shouldn’t have any difficulties.

Carburetor check sequence

On the car we tested, the engine air filter is located directly on the carburetor. Therefore, to gain access it must be disassembled.

• Remove the filter cover using a wrench. We take out the filter element (at the same time check its cleanliness) and unscrew the bolts securing the casing to the carburetor. Remove the body;

• Let's look inside the carburetor. Depending on the engine temperature, the throttle valve may be open or closed. In the second case, we open it by hand. Then we press the throttle mechanism drive and check whether a stream of gasoline appears from the pump;
• After making sure that there is gasoline in the carburetor, we get into the car, press the gas, and try to start the engine. If it doesn’t start, look further;
• Remove the top carburetor cover so that the fuel level in the carburetor chamber can be seen. The cover is secured with 5 screws. You should also disconnect the throttle cable bracket and turn off the idle air valve;
• Having released the float chamber, we assess the gasoline level. During normal operation of the fuel supply system, the level should be 23 mm below the walls. You can estimate the level using the tail of a caliper, having previously set it to a depth of 22-23 mm;

• We put the cover back on, fix it with a pair of screws, and start the engine again, having first depressed the gas pedal all the way;
• If the chamber is empty, the verification algorithm is slightly different. We put the lid on, leaving a small gap between the upper edge of the float chamber and the plane of the lid. We fix the gap with a flat steel ruler or a small screwdriver;
• We fill the chamber by manual pumping or by turning the crankshaft a few turns with the starter. After filling the chamber, we try to start again, having first secured the lid;
• The motor starts working - this is a sign of a malfunctioning needle valve. It should be replaced because it is almost impossible to restore it.

A tested and restored carburetor can be assembled, although it would be more correct to dismantle it (since you got to it anyway) and wash all internal parts with acetone.