# Stihl FS 55 string trimmer wont stay running



## Brian N.E Ohio

My FS-55 string trimmer will start but wont stay running. It will run for 5-10 seconds and then stall out so I know it has spark. I could not get the primer ball to fill with fuel until today. Now it will start but wont stay running. When the primer ball is pushed I can see air bubbles rising in the fuel tank. Could this be a sign of a cracked fuel line or is this normal? I never looked when it was running correctly. I under stand fuel lines can be a problem with older stihl products. My trimmer is now about 10 years old and this is my first problem. The spark plug looked good.
Other ideas what to look for?


----------



## Brian N.E Ohio

I am using a public computer and will try to check back daily at least once for a few days. I am on my way to my dealer to see if they are willing to help me diagnose this problem with out a visit to their shop.


----------



## Huntinfamily

Fuel filter might be clogged. I had the same problem with my chainsaw, gave up trying to fix it and took it to a mower shop. They replaced all the fuel lines and the filter, runs great now. Guy recommended that after each use I pour any remaining fuel out of the tanks and try to start it a few times to clear any remaining fuel out of the lines. The ethanol in gas makes the gas go bad faster than it used to


----------



## flewism

Look at the filter at the end of the fuel line in the tank, Then the fuel line in general , it should not be soft and kind of gummy, it could be collapsing closed.
Disassemble the carb and clean it well, and or get a rebuild kit, they are cheap.
If you are not used to rebuilding carbs take a lot of pictures during disassembly


----------



## flewism

Also I'm not sure if your trimmer has a built in or external impulse line. This will be a second plastic hose running from the lower crankcase to the carb if it is external. Make sure it is hooked up and not leaking as this line supply's pressure/ vacuum to the carb for the fuel pump.


----------



## alleyyooper

Did you store it with fuel in the tank? If so you have a gumnmed up carb and possiably lines. You can put fresh gas and*sea foam *in it and keep starting it and allowing it to run as long as it will. sooner or latter it will clean up and keep running. Best bet and saving the cranking your arm off it to tear down the carb and rebuild it after a good cleaning.

Findings are todays gasoline isn't much good after as short of time as 30 days. Mixing stable is recommended when storeing fuel in equipment.



 Al


----------



## Brian N.E Ohio

Disassemble the carb and clean it well, and or get a rebuild kit, they are cheap-

I have rebuilt one carb in my life. It was a Rochester monojet on an old chevy malibu circa 1976, a simple dis-assembly and cleaning of the bowl and resealed with new gaskets. Never fooled with a 2 cycle carb, not sure how to set it up without a tachometer. Is there a web sight that would help me adjust the settings again?

Fuel filter might be clogged- 

I will replace fuel line and filter if I need to pull them out.

The ethanol in gas makes the gas go bad faster than it used to-

I did not know that. I generally run the fuel out at the end of the year but this year I left 1/4 inch in the tank.

Also I'm not sure if your trimmer has a built in or external impulse line-

I"ll check but don't remember seeing one.

Did you store it with fuel in the tank? If so you have a gumnmed up carb and possiably lines. You can put fresh gas andsea foam in it and keep starting it and allowing it to run as long as it will-

Yes there was fuel left in the tank :awh:. What is sea foam and where can I get it? Auto parts stores? Tractor Supply? Hardware? Small engine shop?

Thanks for the ideas, I'll try the less invasive ideas first. 

Just wanted to let you know the person at the dealer wasn't a lot of help. A new trimmer like mine is $230(yes they still make it) and the shop rate was $72 an hour. Wow.


----------



## Brian N.E Ohio

Also, I use Stihl 2 cycle oil wich is supposed to have fuel stabilizers in it and every drop of 2 cycle mix at my house gets mixed with Sta-Bil at the gas pump, I think its 1/2 ounce per gallon.


----------



## Brian N.E Ohio

Ok, Found the sea foam web sight and it seems to be an auto parts store item.


----------



## alleyyooper

Wally world (wal mart) carries it about $10.00 a can here. I also saw it Mejiers yesterday if was $9.99 a can.

 Al


----------



## agmantoo

Using a small spritzer bottle with a 2 cycle oil gas mix in it start the engine and as the engine starts to fail give the inlet to the carb a shot of the mix to keep it running. Within a few minutes the engine should begin running without the spritzered gas.


----------



## Joel_BC

alleyyooper said:


> Did you store it with fuel in the tank? If so you have a gumnmed up carb and possiably lines. You can put fresh gas and *sea foam *in it and keep starting it and allowing it to run as long as it will. sooner or latter it will clean up and keep running.


Al (and others), just wanted to check on this one point. Some guys say Seafoam is okay to use with all engines, some say good for 4-stroke but _not_ for 2-stroke. They say it will make the oil in the gas mix (when it goes through the crankcase) less lubricating, and hence harm the bearings and or rings.

I've used Seafoam with my 4-stroke small engines, but been reluctant to use it with my chainsaw or weedwhacker. Am I being superstitious?


----------

