Weedeater - Cranks Great Cold, Won't Crank Hot

[DieselDennis]

I have a ten year old Stihl FS80 weedeater.  

I can literally take it off the hook after hanging for 1-2 weeks, push the fuel primer bulb three times, flip the choke on and crank it in 1 or 2 pulls.  I have been able to do this repeatedly.  

After I get it cranked the first time, the weedeater runs great.  Revs high and cuts fine.  

Now if I stop to open a gate or look at a neighbor and let the motor go dead, I can pull on it 30 times and won't be able to restart it.  Choke off/on, fuel bulb pumped/not pumped, doesn't matter.  Won't run whatsoever.

What gives?  What am I doing wrong here?  Like I said it cranks great cold and runs fine.  Only give it a diet of non-ethanol gas.

[MikeBob]

I am thinking carburetor vapor lock. The engine is hot, the gas in the carb vaporizes and not a liquid. Just my guess, not a small engine guy. Just a bit of knowledge.

[Wild Turkey]

Try loosening the fuel cap if it won't start hot. They changed their caps a few years ago but I don't remember why but I seem to recall something about hot starts.

I've got a FS110 and it's a workhorse!

[MikeBob]

Fuel cap change., might need venting or was not venting, just a guess, for how little I know but sound logical based on other small engines I worked/dealt with.
Riding mower lost the gas cap, so I figured some plastic wrap with a rubber band, I would get 5 feet and engine was fuel starved no vent in it for the gravity feed, popped a hole in the plastic wrap, good to go, I found the cap next grass cutting.
My advice is always call the manufacturer for advice/answers, not Forums for guesses and opinions.

[Mags®]

Sounds to me that you have an ignition module issue.  Over time, especially if you tend to run the unit with too long of string, the module will start to overheat and distort the firing sequence.  The only solution is to replace the module if that is indeed the case.  Unfortunately there is no definitive diagnostic test to determine if a module has gone bad, only option is to replace with new and see if it fixes the problem.  Generally speaking the part is in the $60 dollar range and can be replaced by a homeowner with the right skills.  There is a specific gap tolerance that must be set when replacing the module, so don't just slap one on without setting the gap.

[daddo]

I'd start simple. Replace the plug, fresh gas, see that the bulb or fuel line has no holes in them, the gas cap vents, clean filter.
I had to replace the carb on mine and the fuel line.

[DieselDennis]

Sounds to me that you have an ignition module issue.  Over time, especially if you tend to run the unit with too long of string, the module will start to overheat and distort the firing sequence.  The only solution is to replace the module if that is indeed the case.  Unfortunately there is no definitive diagnostic test to determine if a module has gone bad, only option is to replace with new and see if it fixes the problem.  Generally speaking the part is in the $60 dollar range and can be replaced by a homeowner with the right skills.  There is a specific gap tolerance that must be set when replacing the module, so don't just slap one on without setting the gap.

Mags,

I replaced the ignition module last year due to a no spark at all issue.  I did pull out my feeler gauges to set the gap on the new module as instructed. 

Guess I'll crack the gas cap and then start throwing money at it.  The ignition module I replace last year has been the only money I've ever spent on it. 

Or I may just let it sit til spring and worry about it then.  The leaves are beginning to fall here.

[daddo]

We have a winter weed grass that comes in, so I'll be mowing much through the winter in spots and weed eating once a month.  
Why can't I get a break?

[tomsteve]

recheck the gap.

[AUswimKC]

We have a winter weed grass that comes in, so I'll be mowing much through the winter in spots and weed eating once a month.
Why can't I get a break?



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