Stihl FS-55 Won't start.....

[Nonprophet]

I bought it new 4 years ago. Always run clear premium fuel in it--always run it dry (dump out gas, run until it's out of gas...) every fall.

Needed to cut down some blackberries a few days ago. Put in some fresh gas/oil mix, tried to start like normally do. Primer bulb was not filling with fuel. It's been in the 20's at night lately, brought it in house from shed to warm up. Next day, try to start. Primer bulb fills with fuel, pops with full choke, runs 5 seconds, then dies. Try to restart--no luck. Check spark plug, it's wet. Dry it off, wait a few hours. Try to restart, same thing--starts, but dies quickly. Small amount of fuel coming out of muffler. Pull spark arrestor--it's pretty plugged up so I clean it with wire brush. Check fuel lines, and notice that the thin, straight one is getting pinched by the throttle cable. I re-route it a little so that it's not pinched, try to start, nothing. I pull off the fuel lines (I have the green ones) and check for leaks by pulling off and blowing air through them, no leaks. Replace fuel filter. Try to start, nothing, still seems to be spitting some fuel out through the spark arrestor. Figure carb must be gummed up, pull it off, clean it (carb spray, then compressed air through passages), re-assemble, still won't start. Borrowed inline sparkplug tester--spark seems fine, still won't start.

Any suggestions?

Thanks!

 

[indiansprings]

New carb cost only 31-32 dollars, ten to fifteen minutes change, we don't even mess rebuilding them anymore, you can do it yourself ez, do it and it will run like a top.

 

[Nonprophet]

New carb cost only 31-32 dollars, ten to fifteen minutes change, we don't even mess rebuilding them anymore, you can do it yourself ez, do it and it will run like a top.

Hi Indianpsrings,


I'm happy to put a new carb on, but are you sure that's the problem? Would suck to replace the carb only to have that not be the problem...

 

[indiansprings]

The condition your decscribing is your inlet needle is shot, the inlet neele seat is shot or your check valve is shot all in the carb, do it everyday for a living see it all the time, you carb is shot, can't rebuilt the check valve, cheap way is to replace the carb, trust me.

 

[Fish]

Dump out all of the olf fuel, and try to start it for a few dozen pulls. Iust to get rid of the old fuel. If it starts and dies, then it is a carb problem

If not, after the few dozen pulls, remove the air filter, then spray some fuel in the carb throat, and pull some more, tell us what happens....

 

[ol'homey]

I have replaced a few coils on the Stihl trimmers that were bad. All of them had spark but the timing was off. They would make a pop every now and then but that's it, fuel running out the exhaust and the owner turning blue from pulling on it. New coil, set gap with a business card and she's up and running like a new unit. After you've ruled out the carb, try throwing a coil on it and let us know what happens.
PS- If it's running for a few sec on the prime it's NOT the coil. The bad coils I've seen will pop just enough to keep you pulling on it thinking it might start but never does!