A chainsaw does not get gasoline in the carburetor
Not getting fuel into the carburetor of a chainsaw
The chainsaw carburetor is the element that is responsible for mixing the air-fuel mixture. Not only the engine’s stability, but also the chain saw’s speed depends on the condition and condition of this important assembly. Therefore, every owner of a garden tool should study the design of the carburetor, as well as familiarize himself with the rules of its maintenance and repair.
Most modern chainsaws have almost identical carburetors. They are virtually identical and work on a similar principle. The only difference between the chambers from different manufacturers lies in the material from which they are made. In expensive chainsaws of American, Swedish and German manufacture, chambers are made of reliable alloys that are coated with protective coatings. Cheap Chinese and Korean chainsaws are equipped with units made of cheap materials.
Each carburetor consists of the following components
- An aluminum housing with a one-piece design. Inside the housing is the inlet fitting, the main screw, the pulse channel, the bolt to adjust the engine when idling;
- throttle valve. it is responsible for adjusting the amount of air required to enrich the fuel mixture;
- diffuser. it is located near the chamber inlet;
- atomizer is designed for supplying the fuel mixture directly into the carburetor chamber;
- Float chamber. it has a float, which is triggered in the case of insufficient amount of fuel;
- nozzles. they are valves, which are responsible for adjusting the fuel quantity.
This scheme of a chainsaw carburetor is as simple and effective as possible. In some models of garden tools, it can be supplemented with additional spigots, glands or filters.
The principle of operation of a chainsaw carburetor is quite simple. At the moment when the engine is started, the air flap at the bottom of the housing opens. In the float and air chambers, a vacuum is created by the movement of the piston. This triggers the stock diffuser, which begins to draw in air. The amount of air intake depends on the degree of opening of the choke. When the piston actuates, fuel begins to flow into the chamber through the inlet connection. Its quantity and flow rate depend on the position of the jets.
Later on the fuel in the air chamber begins to mix with the air. After that, the ready air-fuel mixture passes through the intake valves, from where it is sent to the combustion chamber of the saw engine.
Adjusting the chainsaw carburetor. what the beginner needs to know?
Initially all adjusting bolts are in their factory positions. this ensures that the optimum amount of fuel and air is sucked in. After the carburetor has been running for a long time in harsh conditions, however, the factory settings of the carburetor may be compromised. Even a slight shift of one of the bolts by 1/5 of a turn will lead to a serious malfunction of the saw engine. In this connection, the operator should always make sure that the adjustment bolts are in the optimal, factory-set positions.
If for some reason the operation of the node has been disturbed, it will need to be readjusted. There are 3 adjusting screws in the unit for this purpose. The first of them is marked with the letter H. it is necessary for adjusting the chainsaw engine when working at maximum rpm. The second screw marked L is used for adjusting the motor when it works at low RPM. The third screw may be marked T, S or LA. Its task is to adjust the engine when working in idle mode.
The chainsaw carburetor must always be adjusted with the engine in good working order. Immediately before adjustment you will need to inspect the air filter, and if necessary, clean or replace it.
General device of the chainsaw
There are many models of gasoline saws on the market from different brands. Products from different manufacturers differ from each other by design and technical characteristics that determine the ergonomics and functionality of the equipment, but at the same time the tool has the same device.
The chainsaw consists of the following structural elements:
- internal combustion engine;
- ignition, fuel supply, air filtration, and chain lubrication systems;
- the chain brake and the chain tensioning mechanism.
A schematic diagram of the chainsaw is shown in the photo below.
A carburetor engine runs on a mixture of oil and gasoline. A diagram of its operation is shown in the photo below.
Fuel mixture components are mixed proportionally. The ratios between them are given in the user manual (oil to petrol from 1:20 to 1:50 respectively). The quality of the fuel determines the length of time the tool can be used without repair.
Modern petrol saws in the expensive category often have an oil tank. Mixing it with gasoline in these modifications is automatic.
Why isn’t there any gasoline in the chainsaw??
According to the reviews of owners of Chinese chain saws, the equipment quite often breaks down and the breakdown is accompanied by a lack of fuel supply to the carburetor. If you have applied the above tips, it is necessary to carry out a diagnosis of the following elements:
Carburetor needle. In cheap chain saws the carburettor needle often gets stuck and prevents fuel flow. Sometimes it’s enough just to wiggle the needle and set it right.
Oil Seals. Chinese and even branded chain saws can have low-quality glands with poor sealing. Fuel stops flowing when the mixture starts to squeeze out through the seals. There may well be gasoline leaking through the seals.
Checking the breather plug
Exactly the breather plays a serious role when starting up the chainsaw, you can find such a detail near the gas tank lid, and more precisely in the area of the air hole. The breather plug performs a simple but important role. it keeps the fuel from leaking out and sets the correct air pressure. It is through this air that the fuel enters the carburetor, and a malfunction of this element is a common cause when the fuel does not flow into the chainsaw. A defective breather will create negative pressure that prevents gasoline from getting to the carburetor when you try to start the tool.
Check the serviceability of the breather is simple enough, disconnect the gas tube from the carburetor and check how the fuel flows. If gasoline leaks in a small trickle, everything is fine, if it does not leak at all, the breather plug is probably clogged with mud. If done properly, the part can be cleaned, sometimes it’s easier to replace with a new one. The cleaning procedure is performed either manually or by a strong jet of compressed air.
180, which has shown excellent performance and reliability. Here were all the best practices of the German company, weighing 3.9 kg chainsaw easily perform work in the garden. It is easy to cut small trees, branches, you can even prepare firewood. But even the best quality equipment tends to malfunction, and so it happens that the STIHL chain saw 180 will not start or will not start with great difficulty. We’ve tried to compile all the causes and repair methods for the German STIHL 180.
What’s on your mind?
Features of this saw. the pride of the German manufacturer. In this case, the unit. is a tool that is designed to perform a small amount of work. The tool is positioned for home use, which confirms the intensity of its use, which should not exceed twenty hours per month. With such a tool at your disposal, it is not difficult to keep order in your garden, make firewood for the winter, as well as to clear areas. At the same time it can help you with other tasks, where there is no need to perform complex manipulations.
- For many owners, the question about the correct idle speed after draining the fuel from the gas tank is relevant. According to experts, you don’t have to worry about it. However, if you often have to deal with such a problem, it is enough to manipulate the carburetor, reducing the engine speed, to restore normal operation of the tool.
- In some cases, the owner may need to clean the muffler, as this part may be the cause of the malfunction. This operation is simple enough. It should be remembered that many owners encounter problematic chainsaw operation due to a faulty carburetor.
- Although in some cases it may be fairly easy to fix the malfunction, it is preferable to have professionals repair this equipment. Because not all of us have the necessary knowledge and skills, and it is fraught with the fact that when you fix problems yourself, there is a risk to completely disable the tool.
It is also necessary to check the fuel hoses, including the return hose and the “pear” of the manual fuel priming to check if they are not clogged with anything, if these hoses are not leaking and there is no air drain in the fuel supply elements.
Replace the fuel filter in the tank (coarse fuel filter) before refueling.
Clean the air filter element to ensure that the carburetor is properly adjusted and gives enough air for the motor to work properly.
Before you clean a chainsaw carburetor, you must drain all the fuel from the tank. If the fuel is dirty or old it’s better to get rid of it and fill up the chainsaw or weed trimmer with good-quality clean fuel (good 95 gasoline, good 2-stroke oil mixed in the right proportion).
The structure of a chainsaw carburetor
The carburetor of any modern chainsaw is an integral part of the engine, which continuously adjusts the amount of air needed to continuously mix with fuel, and feeds the mixture into the cylinder of the engine.
In most modern chainsaws built-in carburetors initially have a similar device and almost the same principle of operation. Certain differences exist only in the fuel units of Chinese models.
The main elements of the carburetors of all chainsaws include:
- float chamber. a small compartment whose main task is to maintain an optimal amount of fuel filled
- The atomizer is an important mechanism that is initially responsible for injecting fuel into the intake air flow;
- diffuser. located near the regular inlet, through which the air enters the engine compartment of the chainsaw. The main function of the diffuser is to forcibly accelerate the intake of air masses;
- tube. required for supplying air in small volumes. portions, the size of which depends on the needs of the fuel system.
The principle of operation of the chainsaw carburetor is also quite simple. When the chainsaw is running, the engine throttle is actuated, which, when open, lets air in through the factory rubber tube. With gradual opening of the regular flap and the tube connected to it, the float, located in the chamber with the filled fuel, is activated. Continuously passing through the nozzle, the air mixes intensively with the fuel. After that, the used ready air-fuel mixture is sprayed into the working cylinder of the regular engine through the factory intake. During the fuel spraying the pressure inside the float chamber is practically identical to the atmospheric pressure. At the same time, the pressure in the factory air tube is rarefied. Because of the difference in these rates, the air is continuously sucked in by the tube. the engine needs more fuel at higher rpms. Accordingly, the tube must suck in more air. So it is the carburetor that largely determines the engine’s ability to intensively gain the rpms required for sawing large wood.
adjusting a chainsaw carburetor
This procedure is needed specifically in those cases where the household garden tool does not start or, after starting, immediately stalls. Tuning the carburetor of a chainsaw is also needed when its power has dropped or the amount of fuel consumed has increased markedly.
For independent adjustment, each manufacturer includes adjusting screws in the set of its garden equipment. The bolt marked with the letter H is used to adjust the position of the main nozzle and operation of the engine at high revolutions. The L bolt is needed for basic adjustment of the position of the engine-created idle speed nozzle. Accordingly, the screw T is required by the owner of a chainsaw to quickly adjust the work of the factory engine at idle speed. In some cases, this screw is also marked with the letters S or LA.
Some chain saw failures are caused by improper venting of gases produced during fuel combustion. An example is when there is a lot of smoke at high rpm, as well as unstable operation. Because of the large amount of soot and mechanical damage, the muffler’s exhaust silencer capacity is significantly reduced: the cleaning of soot is carried out as follows
- Perform disassembly, which necessarily closes the exhaust port.
- The silencer can be disassembled and check its internal condition. However, in some cases, the structure is not dismantled.
- You can clean the internal space from carbon deposits with special substances. Less commonly used dry method, which involves mechanical action.
After cleaning the construction, it should be thoroughly dried. Drying can be accelerated by using a construction hair dryer. When reassembling it is necessary to open the outlet opening.
Why chainsaws do not start well
Let’s consider each cause in more detail.
Fuel and air filter
Dirt on a chainsaw’s main filter element negatively affects the chainsaw’s performance.
For example, a dirty air filter, will provide air to the carburetor not in full, which will affect the quality of the fuel-air mixture and normal engine start. The fuel filter becomes clogged, making it difficult or even impossible to get gasoline into the carburetor and run the engine.
One of the most frequent cases of chainsaw starting difficulties is the wearing of the cylinder block (piston group).
As it is known, for normal start of a chainsaw in its engine there should be compression. It is necessary for normal compression of the fuel mixture in the engine cylinder, as well as it affects the work of the gasoline pump.
The chainsaw becomes difficult to start because the compression value will drop while in use.
The reasons for the lack of compression, or its decrease, can be natural, t.к. the engine wears out during operation. Problems can also be caused by a serious failure, such as a scuffed cylinder block or a broken piston ring.
a sign of low compression, is a weak resistance of the starter motor when starting. If compression is low, the chainsaw has less power, which negatively affects its performance. The problem can be eliminated by replacing the piston rings or the entire cylinder block.
Adjusting the carburetor
Improper carburetor adjustment will cause the chain saw not to develop full power. Will not start well or will not start at all. Adjusting the carburetor directly affects the quality of the fuel-air mixture, which is necessary for normal starting and further engine operation.
Improper carburetor adjustment causes the fuel-air mixture to contain more or less gasoline than needed, and the mixture will not ignite even with normal spark formation.
The excess of gasoline in the mixture, is called the overflow. Typical sign of an overflow is a wet spark plug, after several unsuccessful attempts to start the chainsaw.
The spark plug is one of the main components of the ignition system. On its electrodes is the formation of a spark, and if the failure of this element, to make start will be difficult or not possible.
The spark plug may fail completely, or work intermittently or give a weak spark. Checking the spark plug is simple enough, you need to unscrew it from the engine, connect it to the cap of the high-voltage wire and, putting it on the cylinder, pull the starter. If the spark plug is in order, the spark will be powerful with a bluish tint. Weak spark with a reddish tint, a sign of a problem. Defective spark plug must be replaced.
The reason that a new chain saw does not start, or starts badly, may be the ignition coil. Modern chainsaws, are equipped with electronic ignition coils. This part can not be repaired, and, as a rule, if there is a defect, it is replaced completely.
The gap between the ignition coil and the flywheel
A wrongly adjusted gap between the flywheel and the ignition coil contacts affects the quality of the spark formation, which in turn is responsible for a normal start and stable engine operation.
The chain saw does not start when hot
In those cases when the chainsaw does not start in the hot, it is necessary to carry out a visual inspection of all the major components of the chainsaw. The inspection should start with the spark plug. Check the spark, inspect the surface of the spark plug electrode, these actions will help determine the direction in which to look for the problem.
Faults in the ignition system
If an inspection revealed that the spark plug is wet and spark formation on the contacts does not occur, it means that the problem should be sought in the ignition system, inspect the coil, check the gap between the flywheel and coil contacts. You can also check how tightly the cap of the high-voltage wire sits on the spark plug, and the plug itself. Try to replace the spark plug with a new one.
Problems in the Fuel System
If the examination shows that the spark is on, but the spark plug is dry, then the problem is in the fuel system. It is necessary to start with the fuel filter. Next, you need to inspect the fuel hose and its attachment to the carburetor, pay attention to fuel leaks from the carburetor and the presence of gasoline in the air filter housing. You may start to remove the carburetor only if visual inspection did not determine the cause of failure.
A typical sign of a problem in the fuel system is an excessive amount of fuel in the engine cylinder. As a rule, the signs of it are excessively wet spark plugs and the presence of spark on the contacts of the plug. If this happens you need to turn the machine over so that the fuel plug is facing downward. If you can see petrol leaking from the cylinder it means that the chain saw won’t start because the fuel is overflowing into the engine.
“Fills” with fuel, sometimes due to improper adjustment of the carburetor, or its malfunction.
To learn how to adjust the carburetor, watch the instruction video on the Champion 254, for example.
What to flush a chainsaw carburetor with?
To think about cleaning the fuel assembly of the gasoline tool should be in such cases:
- when the engine is difficult to start;
- when the engine is working unsteadily at a short idle speed;
- In the case of the appearance of slack when the regular gas trigger is pressed smoothly;
- when there is a significant increase in fuel consumption.
Most often, for flushing the built-in carburetor of a chainsaw, liquids are used, which are available in almost every garage:
Modern gardeners who use powerful professional saws use a more effective and gentle product:
- Mannol Vergaser Reiniger, a cleaner that is sold as an aerosol. It quickly and easily breaks down even the oldest formations of tar, carbon deposits, oily plaque and other types of contaminants;
- Hi-Gear. this cleaner is distinguished by its high dissolving properties. It can remove old dried-on stains, oily crusts and the first signs of rust without harming parts of the fuel system;
- Jet 100 Ultra is a high-tech spray designed for quick cleaning of a chainsaw carburetor. Shows a high rate of dissolving the oldest oil stains.
Cleaning the carburetor on a chainsaw is done in this sequence:
- First you need to clean the outside of the saw’s engine, as well as dismantle and thoroughly wash the factory air filter housing;
- Then you can proceed to the disassembly of the gasoline tool. To do this, you need to remove the filter housing, as well as unscrew the fasteners that hold the carburetor together with the engine;
- Then it will be necessary to carefully disconnect the pull rod and throttle cables from the carburetor. The springs available in the structure must be removed so as not to stretch them;
- After that, you need to carefully pull the fuel hoses off the factory fittings of the fuel assembly;
- To clean the carburetor on the chainsaw, you need to remove it from the branded fastening studs. It is important to maintain the integrity of the gasket installed between the internal combustion engine cylinder and the fuel assembly;
- The next step is to clean the outside walls of the carburetor. To do this, they can be treated with a liquid cleaner or gasoline. At the same time, you should try to make sure that dust and debris do not get inside the node or motor cylinder;
- Next, it will be necessary to unscrew the screws fixing the carburetor diaphragm, remove its cover and wash the inner cavity with an aerosol cleaner;
- After that you need to dismantle the fuel pre-fine filter, as well as disassemble the part of the unit, to which the fuel is supplied. All internal parts of the carburetor should be thoroughly washed with an aerosol cleaner. If the first cleaning did not bring results, then the flushing should be repeated.
After the final drying of all the internal parts of the regular carburetor you need to assemble the fuel assembly in reverse order, and install it in place in the construction of the utility chainsaw.
Chainsaw Ignition System Faults
Malfunctions in the ignition system are the most common cause of gasoline tool engine failure. That’s why you should start troubleshooting there. Inspect the spark plug. To do this carefully remove the spark plug wire from the head, and then unscrew the plug from the socket using a special wrench. If the spark plug is wet, it means that there is excessive fuel. often than not, an excessive amount of fuel is caused by improper carburetor adjustment or ignition system problems. Wipe the spark plug thoroughly with a dry paper towel and let it dry. Also dry the cylinder, close the fuel supply and restart the engine several times to remove the excessive fuel mixture. After these actions it is necessary to install the spark plug in its place, open the fuel supply and try again. If you notice a lot of black sludge on the plug, it usually indicates malfunction in the fuel supply. improper gasoline / oil ratio, poor-quality oil or the need to adjust the carburetor. In this case you need to clean it with a needle or a sharp needle from accumulated sludge, clean electrodes with sandpaper until it has shiny metal surface and screw it back in place. In this case you should pay attention to the tightness of the spark plug gasket. If the chainsaw still won’t start, you need to check for spark in the spark plug. With the cap on the spark plug wire lean the skirt of the plug against the cylinder and yank the starter as shown in the photo below:
If there is a blue spark from a distance of 2-3 mm, everything is fine. If the spark only appears at a distance of 0.5. 1 mm, the ignition system is most likely malfunctioning. If there’s no spark, you need to check the high-voltage cable with a probe. There might be a wire break in it. If all the steps you took were unsuccessful, try changing the spark plug to a known good one and try starting the chain saw again. Also, the lack of spark may be due to a gap between the ignition module and the flywheel coil. The clearance should be 0.2 mm. The necessary gap can be set with the help of a shim of 0.2 mm, which is placed between the flywheel and the ignition module. A video of the chainsaw ignition device and its malfunction is shown below (click the triangle to play):
Gasoline is not flowing into the carburetor of the chainsaw
If the fuel does not flow into the regular chamber, it may indicate several faults at once. First the air and fuel filter should be checked. If the saw is used for a long time, these elements absorb large quantities of dust, which then prevents the flow of clean air and fuel. A lightly contaminated filter can be cleaned with gasoline, but if the part is clogged with a lot of dust, it will need to be replaced.
Another cause of malfunction is the needle. It is very difficult for this part to stick, particularly in a Chinese-made chainsaw. To fix the problem, in most cases it will be enough just to move the needle.
If there is no fuel coming into the chamber, the saw owner should check the oil seals on the tool. After several months of tool use, these parts lose their tightness. Over time they start leaking gasoline, and that can lead to the tool not starting. Repair by replacing the packings.
The breather plug plays an important role when starting a chainsaw. It is near the gas tank lid and has two purposes. to keep the air pressure at the right level and to keep the fuel at the right level. To check the breather plug, disconnect the fuel pipe and see how much gasoline is leaking. If it is not leaking at all, then the original breather plug is clogged with debris and dirt. In this case it will be necessary to clean the element and install it in its place.
If there is no fuel in the chamber, the fuel line should be checked. Most often, to complete a budget-class tool, a Chinese hose is used, which over time loses its tightness. In such a case, you will need to replace the line, paying special attention to the tightness of the joints of the channel.
What to do if the chain saw won’t start even afterwards?
If the initial inspection did not give anything or the defects were eliminated during the search, and the chainsaw still does not start, then you need to look for more serious causes. It is better to find out and eliminate such malfunctions in a service center. However, with experience, you can find and fix them yourself. What to Test and Diagnose?
In the first case, checking the compression in the cylinder will clarify the condition of the cylinder and piston group (BCG) of the chainsaw does not want to start in the cold. To do this, you will need a compressometer. The device is screwed in place of the spark plug and an idle start of the engine is made. Measuring the readings gives an indication of the condition of the cylinder head. In the absence of a compressometer, you can determine the compression in a cylinder at a glance as follows:
By putting a finger to the spark plug hole and twitching the starter, you can check the compression in the cylinder
If you feel that the finger strongly retracts into the candle channel, then there is nothing wrong with compression. If there is no compression in the chamber, it is a sign of malfunction. The cylinder and piston group needs a more detailed inspection, which will give an idea of the condition of the piston and cylinder, piston rings and bearings.
Do not start the chainsaw in the cold can also due to lack of compression in the crankcase. The main reason for this is that the gasket between the cylinder and crankcase is damaged. Detecting a lack of compression is quite easy:
- Disconnect the upper tube from the carburetor;
- Pour petrol into the regular cap;
- Dip the removed tube into the fuel;
- Pull the starter a few times.
If fuel is sucked out of the cap when you start the chainsaw starter, there is nothing wrong with compression. If not, check the gasket.
The carburetor may be difficult to start or malfunction with the tool. Screws become loose and air can be sucked into the cylinder while you are sawing. Check that the carburetor is securely fastened. Inspect it for fuel leaks. There are many possible causes. Only a service center can accurately diagnose a problem, fix it, and make fine adjustments to your carburetor.
By going through the step-by-step defectology of the chainsaw engine, you will be able to find the fault, fix it yourself and successfully start your working tool. Do not undertake jobs that you are not sure about. Have your carburettor malfunction diagnosed and repaired by trained service technicians.
How to properly adjust the carburetor on a chainsaw?
To adjust the assembly, set the tool on a hard, level surface. It is best to adjust the carburetor of a chainsaw in a place protected from dust and moisture.
The setup process for the assembly should look as follows:
- First you need to unscrew the screws and remove the blade guard. This will make it possible to inspect the carburetor and, if necessary, to clean it;
- Next you need to remove the original air filter of the tool. If the saw is equipped with an additional foam insert, it also needs to be removed;
- After that, you need a screwdriver, which should screw the bolts marked H and L in a clockwise direction until the stop. This must be done very carefully so as not to break the bolts;
- Then loosen the two screws by about 1.5 turns in the opposite direction;
- Next, you need to start the chainsaw motor and let it run for about 7 minutes;
- As soon as the engine cylinder heats up, you need to start turning the bolt L until the engine starts to work at maximum rpm. Immediately after that, the bolt should be turned by 1/4 turn in the opposite direction;
- Then you need to adjust the motor at high rpm. To do this, connect the electronic tachometer to the engine and start turning the bolt H until the readings on the instrument display coincide with the recommended maximum rpm in the instruction manual of the saw;
- At the end of the tuning process you need to adjust the throttle at idle. To do this you need to slowly turn the bolt T against the hand of the clock until the engine is stable and without dips. If the engine starts to stall, turn the bolt T in the direction of the hand of the clock.
To adjust the carburetor on the chainsaw, you should work as precisely as possible with the adjusting screws. Over-tightening the screws would overload the engine and other important parts of the garden tool.
The chain saw stalls and will not start
If the tool is stalled and does not start you should first check the presence of fuel in the tank. Strange as it may sound, but about this many people forget and, when a similar situation arises, immediately try to repair the tool, which can lead to serious damage.
In a situation where the saw has stalled and there is still gas in the tank, you need to assess how the saw has worked up to that point. Maybe when working at the last moment there was a strange sound, rattle, ringing, there was a loss of power or the tool stopped abruptly. All this will allow a preliminary assessment of the situation.
The engine is jammed
It is quite common to see a situation where the saw was running and suddenly stopped, the cause of which was the engine jamming, which in turn was the result of piston skirt rupture, crankshaft bearing failure, piston pin corkscrew ring or piston ring breakage.
Engine stalling can easily be determined by pulling the starter cord. In the case when the starter does not turn, most likely it jammed, and further repair is possible only in the service center.
Fuel line breakage
Vibration occurs during the chainsaw operation, which may cause damage or rupture of the chainsaw’s fuel line. In that case the chain saw will stop and it will be impossible to start it. To diagnose the problem, you need to inspect the machine and look for fuel leaks.
Overheating in operation could be the cause of a stalled, non-starting saw. overheating is dangerous enough because it can melt the piston in the cylinder and cause the engine to seize. In the first cases of overheating, it is worth to diagnose the tool for foreign air leakage into the engine, and to adjust the carburetor.
Air suction and improper carburetor adjustment affects the maximum engine speed and lubrication, which in turn causes overheating and tool jamming.