Weed Eater Won’t Start When Hot – Solved

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Have you ever seen a weed wacker turn on but suddenly die out when it gets hot? The machine starts out normally, but as soon as you trim, everything comes to a halt. Anytime a weed wacker or weed eater stops due to heat, there is some sort of engine trouble. To figure out the specific problem, we compiled the most common reasons and solutions.

A dirty cooling fin is usually the reason why a weed eater stops running when hot. Another possible cause is a clogged exhaust system, or in the case of cordless weed eaters, not enough power available.

Dirty Cooling Fins

When a weed wacker runs, there is a constant heat transference between the engine and air. This increases the engine temperature and risk of overheating. The cooling fins are designed to eliminate the heat and provide extra space for the heat exchange.

These fins get clogged with weeds, foliage, dirt and other debris. This can lead to overheating and cause gaskets to blow and valves to break. Eventually when the engine gets too hot, the trimmer will stop working.

How to Fix It

You can clean the cooling fins with a piece of cloth, a brush or a Scoky air compressor. Which you use depends on how clogged the fins are. Cooling fins are usually found close to the cylinders, but the location might be different with your weed eater. First you remove the cover and then start cleaning.

Clogged Exhaust System

The exhaust handles the gas output from the system, while the muffler reduces the noise. What these two components do is take out the hot gases inside the engine.

If the exhaust system is blocked by carbon and other debris, hot gas gets trapped in the engine and fresh air cannot flow in. The internal temperature will shoot up and lead to overheating. At some point the weed eater will come to a stop. A dirty exhaust and muffler can also be the reason why your weed eater refuses to rev.

How to Fix It

Use a wire brush to clean the muffler. For the rest of the exhaust system, use a piece of cloth and soapy water. Brush off any stubborn deposits you see. For best results, clean the muffler and exhaust regularly to avoid dirt buildup.

Filter Problems

There are two filters that affect engine performance, the fuel and air filters. Both have to be regularly maintained to avoid overheating problems.

An air filter blocks out impurities in the air to keep the engine debris-free. It works with the exhaust system and prevents the engine from overheating.

A fuel filter prevents dirt, dust and other debris from entering the fuel. Its goal is to keep the engine fuel clear and clean.

Both fuel and air filters collect dirt and carbon deposits. If your weed eater feels too hot to touch or stops when it gets hot, either or both might be clogged.

How to Fix It

Clean or replace the air filter. Remove the air filter cover screws and lift the cover. Take the filter out and check for signs of wear. Replace the filter if it is torn or too dirty.

If the filter is intact, wipe with a wet cloth or leave in a bowl of soapy water for a few minutes. Dry the filter and put it back on. Put the air filter cover back and reattach the screws.

Clean or replace the fuel filter. The fuel filter will be on the fuel line between the fuel pump and tank, or inside the tank itself. Check your owner’s manual.

Use needle pliers to remove the fuel filter clips. Take the filter out. Give the filter a shake to remove any residue.

Hold the filter up and look into it. If there are debris, replace the filter. If there is none, put the filter back on after cleaning it.

At some point, both air and fuel filters have to be replaced. When depends on how dirty the filters get. If cleaning no longer works, it is time to get new filters.

Fuel Issues

There are three possible causes: problems with the gas cap, the wrong fuel mix ratio or defective fuel lines. Each requires a different solution.

How to Fix It

Blocked air vent. The air vent allows air to circulate in and around the engine. If this gets clogged, the engine will heat up rapidly due to lack of air.

The solution is simple. Open the gas cap halfway and run your weed wacker. This frees up the hot air trapped in the system. Be prepared to clean up any debris you see there as well.

Wrong fuel mix. If there is too much fuel, the mix becomes too rich and is vulnerable to overheating. If your weed wacker is a 2-stroke, it needs a 40:1 or 50:1 mix of gas and oil. If you made a mistake with the mix, drain the tank and fill it with new fuel.

Defective fuel line. If the fuel line is leaking, you have to replace it. Unless it is fully functional there is no way for fuel to reach the engine. The good news is that fuel lines are easy to replace.

Troubleshoot the Carburetor

The most common carburetor problem is clogging due to old fuel. But in other cases, the diaphragm could be damaged or there might be some adjustments required.

How to Fix It

Check the diaphragm. Check your manual for instructions on how to reach the carburetor. You might have to remove other components first.

The first thing you will probably see is a lot of old fuel residue. Carefully take the carburetor out of the engine. Refer to your carburetor on how to disassemble it. You have to do this for a thorough cleaning.

Use a solvent-based cleaner to remove old fuel sludge. There are also various carburetor cleaners you can buy. The Fuel Ox Star Plus is particularly good at clearing oil sludge.

If the diaphragm is damaged, get a replacement. There should be one available on the manufacturer website. Consider buying a carburetor kit as it contains replacement parts and guidelines on how to reassemble the carburetor.

Adjust the carburetor. Look for the adjustable screws, which should be marked for low speed, high speed and idle. Use a screwdriver to adjust each one incrementally. Turn one screw by a fourth, then see how the engine responds.

If the engine stalls, adjust again by 1/4. Adjust only one screw at a time and observe the engine. Keep doing this until the engine starts to rev.

Blocked Trimmer Head

As you go through weeds, the string and the trimmer head might accumulate debris. The line might get entangled or the trimmer head could overheat due to the workload. In any of these cases, there are solutions.

How to Fix It

Shut the weed wacker off. Remove debris on the trimmer head. Check the string if it has been tangled. If you took the guard out to get more string, the machine will be prone to performance issues. The best way to deal with this is to keep the guard on.

Not Enough Power

If you are using an electric or cordless weed wacker, it could be due to lack of power. The harder the motor works, the hotter it gets. Eventually if the motor reaches its limit, it will stop.

How to Fix It

Turn the weed wacker off and let it cool down for a few minutes then try again. This time, reduce the amount of weeds you are trimming. Also check for blockages in the system. Make sure the battery is fully charged. If the trimmer is corded, check if the cord is still plugged in.

But the best solution is to get a more powerful weed wacker. If the motor is always stopping when you work, it is a sign that the motor does not have enough capacity.