Experienced gardeners share their insights in answering this question :
First check to see that your fuel lines are in good condition , then if still giving you trouble rebuild carb, Go to smalleng.com they have great rebuild videos.

How to Identify and Fix Common Gardening Problems ?

We provide a variety of viewpoints on how to identify and fix common gardening problems. Our sources include academic articles, blog posts, and personal essays from experienced gardeners :

The carburetor might be clogged. A clogged carburetor is most commonly caused by leaving fuel in the string trimmer for a long period of time. Over time, some of the ingredients in the fuel may evaporate, leaving behind a thicker, stickier substance.
The air filter or exhaust port may be blocked. The trimmer may need lubrication and cooling fins or air passages may be blocked. A cordless trimmer`s battery or charger may be faulty.
A blocked or dirty fuel filter

If your engine is trying to run, or starts and quickly stops, you might want to do a quick air filter check. You need air for your initial spark – and if oxygen cannot move readily through the system you will have problems both starting and keeping your whipper snipper running.

The clutch engages the clutch pads to spin the trimmer head. If the clutch assembly is defective, the clutch will not disengage the clutch pads, and the trimmer head will continue to spin, even at low speeds. If the clutch is defective, replace it. (Note: some string trimmers do not have a clutch.
The most common problem with a strimmer not starting is that there`s a problem with the fuel mix. Double check that you`ve used 40 parts fresh unleaded petrol to 1 part 2-stroke oil (40:1). Check the petrol you`ve used isn`t stale.
So, an air filter might clog over time. Once blocked with dust and debris, it cannot supply the required amount of oxygen to your trimmer` engine resulting in power loss. Find the air filter, take out this component, clean and reassemble it. Replace the part if you cannot reuse it.
The most likely culprit is a dirty or clogged air filter. Issues with your fuel pump or fuel filter can also cause your engine to idle then die with any throttle. If you have an older car, it could also be a bad carburetor.
Usually this is the result of the cutting head being taken too close to objects, e.g. garden stones, paving edges, walls etc. The cutting line must be allowed to rotate freely and the correct diameter and type of line should be used.
If your trimmer won`t turn on, especially if it has not been used recently, you may simply have a drained battery. Plug your trimmer into your charger and see if anything happens. Ideally your trimmer will recognize it has been connected to a power source and charge its battery.
Charge only when needed and never overcharge The Trimmer.
When your trimmer starts and runs on choke, it could be because the check valve in the gas cap is clogged. Start the trimmer and gently unscrew the gas cap halfway off. Turn the choke off and assess. If the engine is still running, that means the gas cap may be the culprit.
First check that you have a fully charged battery – a fully charged battery maximises runtime and also power, and minimises the chance of your mower cutting out in use. The next thing to check for is the condition of your lawn – for best performance, it`s recommended to mow your lawn regularly and to mow dry grass.
Battery is dead

The first thing you should do is check if the battery is charged. After being used for a long period of time the battery power drains. This problem can easily be fixed by removing the battery from the grinder, and putting it into the battery charger.

If the line is too thick or too thin it can continuously feed the line. Make sure you are using the correct line thickness rated for your machine. The trimmer head is the unit that houses the spool, cap and spring, and lever (in some models).
One of the main causes of a malfunctioning throttle body is internal contamination. Due to the contamination accumulated in the throttle body, the throttle valve can no longer move properly, causing problems with the control of the air supply.
Engine Stalling

Even when your throttle body`s blade closes entirely, some air has to get through to the intake manifold. Otherwise, your engine would stall. This air flows through a special tunnel known as the idle air bypass. This bypass provides just enough air to keep your engine running while your car is idle.

You need to buy a strimmer line based on the amount of cutting required. Using a thin cord for heavy-duty work can hamper your productivity because the line will keep breaking. Many people don`t recognise the difference between light, medium, and heavy growth so there is some trial and error involved.
Spark arrestors are screens that limit the size of particles sometimes found in the exhaust gases of outdoor power equipment.
The spark arrestor is located on the front of the muffler with a cover. The cover is attached with a 10 mm nut.
The most likely culprit is a dirty or clogged air filter. Issues with your fuel pump or fuel filter can also cause your engine to idle then die with any throttle. If you have an older car, it could also be a bad carburetor.

Discover Relevant Questions and Answers for Your Specific Issue

the most relevant questions and answers related to your specific issue

Trimmer starts and runs for 15 seconds and stops. won’t start for a few minutes and does the same ,
ANSWER : Check the air filter, replace the fuel if it is last year’s, clean the spark plug or replace. Also lube the blade. Good luck…Lee

Read Full Q/A … : Poulan

Shaft disengages and trimmer head stops spinning. Seems to be disengaging at coupling were attachments hook up. Shaft slides back and forth and when I turn trimmer off and jiggle trimmer then start it back up it works for a while then stops.
ANSWER : Something wrong with your cintrifical force clutch . it is problably set too loose so the the shaft wont engage

Read Full Q/A … : Poulan

Auto feed doesn’t work
ANSWER : Take the end apart and make sure the line is not getting bound up or is not over filled to where it can not move freely

Read Full Q/A … : Poulan

Have to run 326rjx trimmer with choke 1/2 closed?
ANSWER : Most likely need to adjust the carburetor. Consult a technician. This can be tricky and if done incorrectly can shorten the life of the unit.

Read Full Q/A … : Poulan

It starts and runs for a bit but as soon as it hits thicker grass it dies
ANSWER : Joe Hi there. Sadly your trimmer will struggle on thick grass as it’s not made for it. You could try moving the trimmer like a scythe. This will aid it as your cutting bit by bit.

Read Full Q/A … : Poulan

My trimmer slows down when applied to material to cut; on its own it runs fine. its electric & feels like its going to stall when you’re cutting. what gives?
ANSWER : Take it apart and clean the slip rings and brushes

Read Full Q/A … : Poulan

My hedge trimmer will not start… Put in new gas
ANSWER : It’s not getting gas, due to being gummed up with old gas. Remove all of the old gas and mix up a batch of fresh gas&oil. Also get some carb cleaner. Put just a little of the gas&oil mix plus an equal part carb cleaner. Try to start it just to work the new mixture through the carb. You might use the spray start to help pull the new gas through. If it fires up on the new gas&oil&carbcleaner mix, shut it off and let it sit for an hour or two. Drain it out and try just a little gas&oiil without the carb cleaner. If all is well fill the tank. If not, repeat the whole process. If you can’t clear the gum this way you may have to remove the carb to clean it.
Good luck.

Read Full Q/A … : Poulan

Hedge trimmer put away for winter. will run but not stay running. put in new diaframs for carb . same results. i am questioning the gas cap now. is it possible that it can cause a problem with keeping this trimmer running Paul
ANSWER : YES, this system relys on pressure and the ionic nature of gasonline to pull the fuel through the system. If the gas cap is off or damaged where a seal is no longer possible, try taping it up with duct tape and see if that helps

Read Full Q/A … : Poulan