Piston Trimmer Will Not Start After Replacement

Repair sequence

The main rule for detecting a malfunction and repairing a scooter is the step-by-step exclusion of system elements, when identifying the causes of a breakdown in one of them. Search and repair, especially when starting from a starter, must be done in accordance with a strict sequence, where the chain can act as the beginning, and the end, for example, if there is or is not a spark. It is worth noting that you do not need to immediately run after the new switch on the scooter, first make sure that the generator is functioning perfectly, only then test the wiring if there is no spark, etc.

Piston group malfunctions

Having insufficient air compression in the engine cylinder, the scooter will not start well, or will not start at all. Experienced scooters can immediately determine the approximate compression level. The conclusion about the compression value can be made by trying to start the moped with a kick-starter.

When in a certain position more effort is required, it means that compression is present. If the leg does not offer resistance, then the required pressure in the cylinder is not created. For more confidence, use a compression gauge.

Unscrew the spark plug from the cylinder and insert the tip of the appliance into it. Crank the engine with a starter. The compressor will show the exact value of the compression ratio. The optimal compression value is 10 kg / cm2. In the case when the compression in the engine is less than 7 kg / cm2, the piston should be repaired or replaced.

piston, trimmer, start, replacement

My weedeater has spark and fuel but it still won’t start

Reasons for the absence of a spark

Often times, owners may encounter start-up malfunctions in cold weather, although the moped has been driving well in the fall. Initially, it is necessary to unscrew the candle and carefully inspect if there is a spark, oily and color.

No spark in the spark plug

The scooter will not start because there is no spark in the spark plug. In this case, you need to do the following: the candle is unscrewed and checked for suitability. Connected to the ignition coil with a wire. Placed on the cylinder. When the crankshaft rotates, the spark on the spark plug is checked. The scooter will not start if there is no spark on the spark plug, or if there is a spark, but it is not constant.

Reasons for the absence of a spark on the candle

High voltage wire

The most common problem with a wire is that it is exposed in a certain place (broken wire). A working wire should, with the tip removed, hit the cylinder body or other metal part of the engine with a spark.

If not scary, you can check the presence of voltage with your finger, but it is better to lean it all the same against the engine. The broken wire will conduct electricity at the break, not leading to the candle. The bare area should be insulated or the wire should be replaced with a new one.

Ignition coil

Using a multimeter, measure the resistance at the coil contacts. Also measure the resistance between the contacts and the output to the spark plug. The optimum values ​​for the coils of different scooters can be found by the scooter model. For example, the optimal resistance of the primary winding of the ignition coil for the Honda Dio scooter is 0.2-0.3 ohms; secondary winding. 8.2-9.3 kOhm.

Timing faults

This paragraph can be skipped if you have a 2-stroke scooter, because such engines do not have a timing belt. The cause of a timing failure may be carbon deposits on the valves or improper adjustment.

You can check for air leakage by resting your hand against the air filter hole on the carburetor. The creation of a vacuum should be felt with your hand. You can attach a plastic bag to the hole and rotate the engine. the bag should be pulled into the carburetor and tear.

If this does not happen, it is recommended to get to the timing mechanism and defect it. Clean if necessary.

Don’t start the scooter

Spark does not appear on the wire?

In most cases, a Chinese scooter will not start due to current leakage, that is, a spark does not come to the wire at all. Experts note that the reason usually lies in insulation, which is absent in a certain place, which leads to the touch of the bare part to the body of the scooter or other place where all the current goes. You need to solve the problem with diagnostics, first of all, inspect the full high-voltage wire in order to find a bare spot.

If the wiring is intact, the cause of the lack of current will be more serious. The current will not flow to the candle for the following reasons:

  • broken switch;
  • broken ignition sensor;
  • defective ignition coil.

The three above-mentioned details are the main ones when generating and supplying current to the candle, so any damage to them threatens that the 4t scooter will not start. But if there is a spark, and your scooter does not want to start, proceed to the next step. checking the fuel system.

Checking the fuel system

It is gasoline that plays the most important role in whether the scooter starts or not, so sometimes some factors affect the supply of fuel to the carburetor and the engine itself. Fuel can be supplied either in a missing or too much amount, which in any case affects the performance of the scooter. The process of diagnosing the fuel system begins with the gas tank, check for the presence of gasoline, its supply, whether the hole is clogged.

After checking all the fuel lines and the faucet for operability, we proceed to diagnose the carburetor. It is he who often causes improper fuel supply; it is important to keep the carburetor in a fully tuned state without the presence of dirt and other debris. Clean the carburetor and blow through all channels, and you will also need to adjust all the jets. If the 4t scooter does not start after cleaning the carburetor, most likely you have too much fuel.

If you find an excess of fuel, you will see that the candle quickly fills, this does not make it possible to form a spark. You can verify this after diagnosing the fuel pump. If you disconnect the fuel hose and start starting the scooter with the kickstarter, there should be an even amount of gas coming out of the hose. If the fuel pump does not work, the fuel flow is uneven and too much, replace or clean the pump.

Other reasons

In general, there are many reasons why a 4t scooter does not start well, this may be due not only to the fuel system and ignition, experts also highlight that sometimes the scooter does not work due to a damaged CPG or lack of compression. Without compression, the piston will not generate the required pressure to start the engine. In some cases, a simple replacement of the rings on the piston helps; in a more advanced case, you will have to completely change the CPG.

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Why the petrol trimmer won’t start?

The owner of a summer cottage cannot do without a lawn mower or trimmer. But during its operation, situations may arise when this unit for some reason stops starting. And there can be many reasons for this. Let’s find out why the petrol trimmer won’t start.

Why the trimmer won’t start. reasons

To determine why the gasoline trimmer does not start well or stalls constantly, it is necessary to consistently check the operation of all the main components of the unit. This is especially important after long-term storage of the lawn mower. So, the main reasons for this behavior of the trimmer are as follows:

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  • The culprit that the lawn mower will not start may be a poor-quality oil-gasoline fuel mixture. It must be cooked strictly according to the instructions. Saving is not at all appropriate here, since it can lead to the failure of the entire piston group of the trimmer. Do not prepare too much fuel mixture, as excess gasoline will lose its quality over time.
  • You should be aware that petrol trimmers of brands such as Stihl, Husgvarna and some others will not start if they are filled with cheap petrol with a low octane number. Therefore, for such units it is necessary to use only high-quality high-octane fuel.
  • If the trimmer stalls immediately upon start-up, then it may have a flooded candle. In this case, you need to unscrew it and dry it thoroughly for half an hour. Then drain the excess fuel in the chamber, clean the candle from carbon deposits, put it back and try to start the lawn mower.
  • If your new gasoline trimmer won’t start, there may be a lack of spark. And this happens because the socket where the candle is located is dry and the fuel does not ignite. Lightly moisten the thread of the spark plug with a few drops of gasoline.
  • The gasoline trimmer may stall due to clogged air or fuel filters. It is best to replace such elements with new ones.
  • The exhaust port and breather can also become clogged. Having cleaned these trimmer elements, it will be possible to start the unit without any problems.
  • Another reason why the petrol trimmer won’t start, even when there is a spark, may be a clogged carburetor. To clean the channels and nozzles, it is necessary to blow them with compressed air using a compressor. Can be used to clean the carburetor and special rinse.
  • If the carburetor gaskets are worn out, replace them. And if the tightness of this device is broken, you will have to identify the faulty carburetor part and replace it.
  • The trimmer may not start due to wear on the piston group. However, it is better to change such parts of lawn mowers in a service center.

Filter check

Another common reason the trimmer won’t start is if there is a blockage in the filter area. To confirm the guess, it is enough to dismantle the indicated block and try to start the unit without it. If the trimmer engine starts, most likely you will have to replace the air filter or at least thoroughly purge the old one. If there is abundant dirt on the surface of the filter element, a new mesh must be used. When resorting to such actions, do not leave the suction pipe completely without a filter. After all, haste in this case can lead to the need to repair the entire piston group of the engine unit.

Troubleshooting strategy

Where to start troubleshooting if the trimmer won’t start? In situations where the tool stalls immediately after starting, it is worth inspecting the following units of the unit:

  • fuel tank;
  • spark plug;
  • fuel and air filter;
  • outlet channel;
  • breather.

It is the breakdown of the above locations that most often leads to the fact that the trimmer does not start well. Let’s look at how to eliminate such troubles.

Outlet duct diagnostics

Stable trimmer performance can be compromised by build-up of dirt in the exhaust duct or blockage in the muffler mesh. This problem most often occurs during the operation of older generation trimmer models. The issue of dismantling the anti-spark grid and cleaning it is being resolved.

How to prevent sudden breakage during trimmer operation?

In order for the unit to always be in a functional state, it is worth following a few simple rules:

  • Conduct a timely, regular technical inspection of the main mechanical components of the device.
  • Fill the trimmer with only fresh fuel, the quality and origin of which is beyond doubt.
  • After each use of the tool, check whether oxides and carbon deposits have formed on the surface of the ignition system elements.
  • Avoid heavy load on the trimmer during work.

In order for the unit to remain in working order, it is necessary to properly prepare it for storage in the winter. First of all, you should completely disassemble the instrument, and then flush and clean the constituent elements. It is also important to inspect functional blocks for damage, if necessary, eliminating deformation of parts, all kinds of distortions, gusts of materials.

Diagnostics of the candle channel

What to do if the used fuel mixture is in good order, but the petrol trimmer still won’t start? The reasons for the failure of the mechanism may lie in the excessive moistening of the candle channel. To diagnose and fix the problem, you need to do the following:

  • Unscrew the candle. Wipe it thoroughly and then dry it.
  • Drain excess fuel in the chamber through the appropriate plug hole.
  • Clean old spark plug if there is carbon deposits on its surface. To cope with the task will allow the use of a regular ladies’ nail file or a file.
  • When installing the element in place, set a gap of 1 mm. To check the parameter, it is enough to place any coin in the gap.
  • Assemble the functional block back.
  • Try to start the trimmer.

It is recommended to dry the candle channel for at least half an hour. However, in no case should you resort to calcining its elements. After all, heating the spark plug can lead to its final damage. What to do if the function block was serviced in accordance with the above recommendations, but the trimmer does not start, there is still a spark? In this case, it is worth treating the threaded connection with gasoline. The latter does not need to be abundantly impregnated with fuel. It should only be slightly damp. Such actions should be taken to ensure ignition. After all, no matter how strong a spark the candle gives, there will simply be nothing to ignite in an absolutely dry chamber.

If, even in this case, the trimmer does not start, it is worth assessing the quality of the contact between the high-voltage wire and the candle. In the absence of a spark (if there is a reliable connection between these elements), the problem is most likely caused by a breakdown of the ignition unit. In this situation, you will have to turn to the services of wizards who will reinstall the node.

Checking the fuel mixture

Let’s say your trimmer won’t start. In this case, the first step is to check whether there is enough fuel in the tank, and also to assess the quality of the fuel mixture. It is necessary to refuel the motorized unit with exclusively high-quality gasoline. It is recommended to use fuel, the grade of which is not lower than AI-95. Filling the trimmer with fuel of unknown origin not purchased from a gas station can cause frequent tool malfunctions. This can cause damage to the piston-cylinder system. In this case, repairs often exceed the cost of the device itself.

Why won’t the petrol trimmer start? Improper preparation of the fuel mixture, which consists of oil and gasoline, can also lead to this. The proportions in which these components are connected are indicated by the manufacturers in the trimmer instruction manual. It is highly discouraged to prepare the fuel mixture in large volumes, that is, for the future. Indeed, with long-term savings, there is a loss of the defining properties of the substance. Therefore, if the trimmer does not start, it is worth draining the old fuel and using a freshly prepared fuel mixture.

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Breather cleaning

Often, the engine of branded trim models stalls as a result of a clogged breather. The main task of the specified component is to equalize the pressure in the fuel tank. In case of contamination of the unit, a vacuum is formed here, which significantly complicates the supply of fuel. The problem can be eliminated by cleaning the breather with a regular sewing needle.

Why won’t the petrol trimmer start? Causes and their elimination

Recently, the gasoline trimmer has acquired the status of one of the main tools in the arsenal of summer residents. And this is not surprising, because the motorized scythe allows you to quickly put your personal plot in order. However, it sometimes happens that the trimmer does not start hot or even cold. In such situations, you have to independently determine the cause of the malfunction. Let’s figure out what to do if the trimmer won’t start. The reasons that most often lead to such troubles will be discussed below.


The breather is a non-return valve designed to equalize the pressure in the gas tank. If it is clogged and does not allow air to pass towards the tank, then a vacuum forms inside the fuel container, and the fuel ceases to flow into the carburetor. To check if the valve is working, remove the hose that goes from the reservoir to the carburetor. If gasoline does not flow out of the tank, then the breather is clogged.

Trimmer users often ask themselves: Where is the breather? This valve is usually located in the gas cap and looks like the following illustration.

Cleaning the breather is very simple: disassemble the valve and rinse all of its components. On some mowers, this valve may be located directly on the fuel tank. It will not be possible to find it right away, since it is hidden from view under the starter housing. Such a breather is cleaned with a regular needle.

Malfunctioning electrical trim tabs

Since the device of an electric mower is much simpler than a motor trimmer, there are few reasons for its failure.

It should be noted that it is better to entrust the elimination of some of them to a specialist.

Basically, the trimmer stops working normally in the following cases:

  • malfunction of the electrical cable;
  • the control button is faulty;
  • burned out motor stator winding;
  • breakage of contact connections on the engine.

Why the petrol trimmer won’t start

The reasons why the petrol trimmer stopped starting may be different, so a step-by-step diagnosis of the device is required.

Fuel tank (fuel quality)

Remember that it is always necessary to check the availability and quality of fuel before starting the unit. In this case, you should not be greedy and save, as well as “be smart” about the amount of added oil. Everything must be done according to the manual attached to the device, since if the piston group fails, its replacement will cost about 70% of the total cost of the trimmer. Fill in fuel on the basis that you will completely use it up when performing work. The gasoline remaining in the tank loses its properties after a while and can harm the engine. Therefore, do not prepare the mixture for future use and in large quantities. If the lawn mower does not start well, try draining the “old” fuel from the tank and refueling it with fresh mixture.

Important! Filling the device with fuel, the origin of which is unknown, is fraught with negative consequences. Gasoline must be of high quality, purchased at a gas station, and its brand must be at least AI-95.

Air filter

If your lawn mower does not start well or immediately stalls after starting, you should pay attention to the air filter, as it can be clogged, as a result of which air does not enter the combustion chamber and the fuel does not ignite. To check if the filter has a case, remove it and try starting the engine. If it works, then the reason has been found. The filter needs to be replaced or well rinsed and dried before installation. In the event that you find oil in the air filter, it must be washed with gasoline, squeezed well and dried for at least 2 hours before reinstalling.

If, however, with the air filter removed, the unit still does not start, then it is recommended to check the fuel filter.

Fuel filter

This filter removes possible contaminants from the fuel. If it is clogged, then gasoline does not enter the cylinder, and, accordingly, the unit does not work or stalls after starting. The fuel filter is located at the end of the intake hose, which is inside the fuel tank. To get to the filter, you need to remove the plug with the tubes coming out of it.

When removing the plug, the suction hose may come off and remain in the reservoir. It is removed with tweezers.

Next, remove the old fuel filter from the hose and put the new one purchased in advance on it. You can also clean the fuel filter if you don’t have a new one. The filter must be secured to the hose with a spring clip.

Place the intake tube on the plug and insert the latter into the tank.

It should be noted that on some trimmer models, the intake hose is not located on the plug, but inside the tank. You can remove it using tweezers or a hook bent from a wire.

Breakage of petrol trimmers

Typical breakdowns of a gasoline trimmer, which the owners of this unit most often encounter, are as follows:

  • engine breakdown;
  • carburetor problems;
  • fuel supply problems;
  • muffler malfunction;
  • breakdown of the gearbox;
  • the starter has broken;
  • air filter problems;
  • gas tank breather clogged.

Exhaust channel

The reason that the trimmer has significantly lost power, and when trying to increase engine speed, it picks up slowly, is often a clogged exhaust channel through which exhaust gases come out of the combustion chamber.

It is necessary to remove the muffler so that no burns get into the cylinder. Next, clean the exhaust channel from carbon deposits.

This must be done very carefully, avoiding the ingress of carbon deposits into the combustion chamber.

After this procedure, the weak power of the unit and a slow increase in the speed of rotation of the mowing head will no longer upset you.

Timing belt worn out

A rare reason, but one shouldn’t be overlooked either. It must be changed strictly according to the instructions. every 50-60 thousand kilometers. Monitor the integrity regularly. If the teeth are worn out or there are many cracks on the part, the camshaft simply will not be able to rotate. Therefore, the car engine will not start even with a new battery.

It also happens that due to the weakening of the belt, the marks are displaced. The result is that pressure is generated in one working chamber, but the electric spark ignites the fuel mixture in the other cylinder. Here it is imperative to set the motor to the tact position, and then carefully check the condition of the marks. If they are violated, the belt must be thrown off, and the camshaft sprocket must be correctly set. The flywheel risk, which is provided on many gas distribution mechanisms, is also obliged to coincide.

A worn timing belt urgently needs to be replaced

In general, it is not recommended to re-try to start the engine with a new battery, a normally working ignition, a working electrical system and an impeccable fuel supply. Taking into account the possible malfunction of the drive belt, this can cause deformation of the cylinders and other internal elements of the internal combustion engine. Better to check the belt right away so as not to make it worse.

Starter problem

But if there are no clicks and other signs of the starter’s operation, there may be a problem with the retractor relay, armature or brushes of the device. You can check with a tester:

  • connect the device to the control cable;
  • activate the ignition;
  • measure voltage.
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The presence of current and the simultaneous heating of the wiring, coupled with the fact that the starter does not turn, and the car does not start, will confirm the guess about the unit malfunction.

It happens, of course, that the lock breaks, but in case of problems with it, the indicators on the display will not light up when the key is turned. It is possible to exclude a malfunction of the ignition and in another way. turn the key to the “on” position, and then turn on the optics. Headlights flashed. lock ok, no. check switch switch.

It will be possible to finally diagnose the starter after removing it. On some cars, it is located extremely inconveniently, access to it is closed. We have to dismantle important components and parts. It takes extra time and effort. First of all, when access to the device is provided, it is necessary to look at the strength of the connection of its terminals. After removal, you need to check the unit directly on the battery.

Checking the starter on the battery

Lack of compression in the internal combustion engine

A low compression level can also affect starting. Visually, this is determined by the increased exhaust gas. As a rule, it falls in white or bluish color. Additionally, idle speed is checked. in such situations it is rarely stable, and oil and fuel consumption increases.

To make sure that there is no compression, you need to use a compression meter. Measurements are carried out with the throttle valve open and closed. Each method gives different results, but allows you to quickly identify defects when the car will not start.

  • The throttle is locked. the compression is about 11-13 bar. This is explained by the fact that little air enters the chambers. If the value is lower, then one can judge about defects in the camshaft cam, general leaks, hanging valves and other defects.
  • The picture will be different after measurement with an open damper. There is more air, which will accordingly contribute to an increase in leaks. The approximate value should be 12-14 bar. This test method is suitable for detecting major malfunctions of the power unit. coking, burnout or breakage of pistons, cylinder scuffing.

Measurement of compression in cylinders with a compressor

Be that as it may, you can fill in about 5 ml of autol, which will immediately increase the compression in general. If it does not help, then the pressure is leaking through the cylinder head gasket. it is punctured and needs to be replaced. Read more about how to check compression here.

Malfunctions in the fuel supply system

The difficulty or impossibility of starting the car after the battery has been replaced is also explained by malfunctions in the fuel system. Fuel may not enter the combustion chamber for several reasons.

  • Broken, the fuel pump does not work well. When the ignition is on, it does not pump fuel, which can be easily identified by the absence of a characteristic working hum. You can also check the malfunction of the unit by throwing off the hose. if gasoline does not flow when the ignition is on, this will confirm the guess.
  • Clogged hoses and filter. We’ll have to disassemble and clean. The coarse mesh is usually replaced immediately.

The fuel pump is located inside the fuel tank. Here he is in direct contact with fuel. This version of the device is called submersible. To remove it, you will have to disassemble the back seat in the car. The element is located under it, on the left or right side of the tank.

The fuel pump is usually located under the rear seat inside the tank.

The fuel system problem is characterized by other symptoms at the same time. Fuel consumption necessarily increases, an unpleasant odor appears, leaks and moisture are observed on top of the hinged system.

Checking the voltage

The electrical component definitely affects the problems with starting the machine. If the battery is new and, accordingly, well charged, and the starter is cranking, you need to look at the voltage in the ignition system. 99%. that the “dog is buried” right here.

What to check if you put in a new battery and the car won’t start:

  • fuses. mounting blocks are located not only under the hood (for example, Mercedes-Benz has an additional black box with a relay);
  • wires. oxidation, breaks;
  • connections. we look at the weakening of contacts, we clean out scale and rust.

Mercedes fuse box

It is the state of the contacts that most often becomes the reason that the car does not start. If there are signs of oxidation on the connectors, then you must first wipe them with a rag soaked in kerosene / gasoline. Then carefully clean with sandpaper or a brush. It will also not be superfluous to check how tight the battery terminals are. It is possible that they are poorly fixed. And, of course, you don’t need to charge a new battery.

Checking the spark plugs

They are necessarily tested if the car does not start after replacing the battery. Better to check the spark plugs right away so you can take fewer steps. As a rule, spark plugs often deteriorate on cars where there is a possibility of flooding. This is caused by repeated attempts to start a car with fuel suction.

Actions when checking candles:

  • turn off the engine;
  • open the hood, wait for the engine to cool;
  • mark the high-voltage cable with a pencil or marker. so as not to confuse the circuit (it is recommended to look at the operating manual of a particular car, since it is difficult to understand the wiring connection combination, especially on 8-cylinder power units);
  • disconnect all high-voltage cables by pulling the cover at the very base so as not to damage the thin rubber;
  • clean the spark plug hole with compressed air or a brush;
  • unscrew the candles with a socket wrench.

Sparking elements must not be wet, black or broken. Any sign that is in doubt is a reason for replacement. After installing a new plug, we repeat the attempt to start the engine.

The spark plug gap is of particular importance. If it is incorrectly set, then the engine will work intermittently, it is difficult to start.

For checking, plate, round and coin-type meters are used. Must be set within 0.028-0.060 inches.

Spark Plug Gap Meters

What to do if the car does not start after replacing the battery

Not sure why the car won’t start after replacing the battery? It is possible that there are problems in the ignition, fuel system, compression. Often such a sign indicates a breakdown of the starter or retractor relay, a broken timing belt or wear of the cylinder-piston group. It is possible to independently establish the cause, but this is not always possible. If you find yourself on the road, then conduct a consistent diagnosis. We could not determine the malfunction. it’s not scary, call a tow truck to the nearest car service.

If the reason could not be established

In 10-20% of cases, the reason cannot be established. At least novice drivers are definitely less likely. What to do? Naturally, take the car to the service station for diagnostics. Let it be done by specialists who have professional equipment and tools. They will quickly find the real reason and fix it.

The battery should by itself be excluded from the list of possible malfunctions, since it is new and does not need to be charged. But it was written above that a weak tightening of the terminals is not excluded. This happens sometimes, so be sure to check.

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If you change the battery, the car will not start, proceed sequentially to find the weak link. Check voltage first, then fuel supply, spark plugs. Starter and compression diagnostics are best done last.