Need help with Stihl FS 110

[bstewert]

I bought this string trimmer new in '03. It gets used about 20 hrs a year, all in the summer months, and I last used it 3 weeks ago. It's always been tougher to start than my other Stihl tools, but now it's totally dead.

So I did the usual simple tune-up stuff, new filters, plug and fuel. I took the old Bosch plug in (USR 7AC). They gave me a NGK CMR 6H and told me to set the gap at .025. It was still tough to start but it did fire up once after a lot of effort. I said great, and put it up for a few days.

Today, nothing. I don't think I'm getting spark. No cough, spurt or nothing. I found the manual, which says NGK CMR 5H at .028 gap. Stores are closed right now, but is that enough to make a difference? The repair shops are all 4 weeks out this time of year. Thanks in advance for any help.

 

[CurSedVoyce]

Yes it makes a difference. Also, you may want to replace your primer bulb... It looks cracked or will be soon. That will also ruin your day.

 

[Old Monkey]

Did it sit with fuel in it during the winter? Fuel destabilizes and screws up tools pretty quickly these days. Its better to purge tools of gas if they are going to sit for a long time.

Checking for spark isn't too hard. Leave the plug in like you have it but make sure its hanging less than an eighth of an inch from the engine casing, pull the chord and look for spark. If you don't see it, pull the plug out, put a screw driver into the coil and set it down so it is near the casing and test for spark again to see if you've got problems with your magneto.

 

[bstewert]

Darin, I usually either run the gas out or dump it, but I have been guilty of leaving it in all winter The trimmer has been used about 5 times since April, so not very much. A couple days ago (when I got it to fire once) I could see spark but it seemed weak. Today I couldn't see any.

I just tried it now, since it's dark outside. This may tell us something. With the plug 1/8th from the case, nothing. With the screwdriver, I get a faint spark every 5 or 10 pulls. It may have a little to do with not being able to hold it the correct distance. How exactly do you do that? What is that black capacitor-looking cube that the wires connect to?

 

[bstewert]

Yes it makes a difference. Also, you may want to replace your primer bulb... It looks cracked or will be soon. That will also ruin your day.

OK thanks. Is it pretty easy to change? I wish Stihl wasn't so stingy on the little tubing to the gas filter. You really have to hold your tongue right to change the filter.

 

[CurSedVoyce]

four screws on the plate around it...easy peasy

 

[SkwerI]

Engine problems can be divided into one of three categories- fuel, spark and compression. If your problem is spark then you don't need to be messing with the fuel side. Focus on the one system that isn't working.

Sounds like a bad coil IMO.

 

[Al Smith]

Couple things here .First on any solid state coil it's a good idea to use a bonding jumper to check the spark .This is just wire attached to the plug and ground ,the engine frame .The reason is that on occasion by just dangling the plug and jumping the spark could raise the voltage in the coil to a point it gets damaged .Sounds silly perhaps but that what I learned in Briggs and Straton factory school .

It's also a good idea to remove all the wires such as the kill switch when checking the coil to eliminate the possibilty that one of them is causing the malfunction .

I'm in agreement with others that it sounds like a bad coil .Remember though you have to pull that engine over so the rate of movement equals about 500 RPM .Briskly now .

 

[bstewert]

I tried a Google search for the coil and came up empty. Also couldn't find a detailed parts breakdown for this machine.

 

[pigwot]

Check with the Stihl dealer to be sure, but I think 4180-400-1300 is the Part# for the coil on the FS 110:

http://wgz-cb.weingartz.com/weingar...?cg=700&cd=&SKUTYPE=202&SKUFLD=SKU&WEBID=3605


http://www.barrettsmallengine.com/stihl/fs110.html

 

[bstewert]

Thanks for the links Pat. Today I tried Al's suggestion of a bonding jumper to the frame, and the kill switch wires disconnected. Nada, zip. Totally dead. The cable to the plug is hermetically sealed to the coil, so the replacement should take care of both possible trouble spots. I'll see if the local dealer has one tomorrow.

 

[Al Smith]

It's fairly easy to find the parts lists for Stihl chainsaws but not so easy for the rest of the power equipment they make .

As far as that coil I would imagine the dealer could get one .Being Stihl the price will be rather steep .It could such a thing as they used perhaps a coil that was also used on small saw engines but trying to determine that has left me for one in the lost lane .I couldn't find diddley squat on the internet .

 

[CurSedVoyce]

Just bought an FS 250 coil and it ran under 70.00 at the dealer.

 

[Old Monkey]

A dead saw or weed eater is worth a mint in parts. Has anyone ever figured out how much more a Stihl chainsaw would cost if you bought it part by part?

 

[CurSedVoyce]

In my IPL and shop manuel it lists a tool and not a setting.. I will dig deeper...
On my FS250s it is .020 inch. Plugs too....

 

[CurSedVoyce]

The plug gap is listed as .028 So that should at least give you a range to try... try it at .028 and work toward .020 if it does not run proper.

 

[bstewert]

Can someone help me with the gap settings on the ignition module? I can't figure out Stihl's instruction sheet. Thanks!

 

[CurSedVoyce]

Service book says the gap on the plug is .028 in...
My FS 250s are .020 for both air gap on the ignition coil and plug. I would try the .028 for the coil gap and work towards .020 and see how it runs.
Betting on the .028.
The book only lists a tool and not an actual measurement.

 

[Al Smith]

Wow 20 thou seems to be a long way .Most saw engines are set at 12 thou more or less .That's about 4 or 5 thicknesses of printer paper .

 

[pigwot]

My grandpa was a low tech sort; used a piece of the thin, glossy-sided cardboard that the coil came in to set the air gap -
maybe that cardboard was about 5 sheets of paper thick?

 

[Ax-Man]

Seems odd that a module would fail but it is possible. .028 spark gap is a little wide to me. Most of that Stihl stuff is .20. Air gap about .015 thou.

I would be checking that carb also. They can give you fits and waste alot of time because a bad carb especially a Zama carb can act like the machine has other non carb problems. I have just about given up trying to fix them and have just started replacing when the machine starts running squirrley. Carbs can run from as low as $30 up to almost a $100 like the one I just recently replaced on my MS 200 rear handle. At least it runs right again and is a pleasure to use. I'd bet that 110 has one of the cheaper carbs.

 

[bstewert]

OK, here is the answer I got from the technical adviser at Stihl:

Bob,
This page only refers to the plastic spacers used under the coil.
If the mounting points are 6.7mm long, the plastic spacers are not used.
If the mounting points are shorter, the plastic spacers are used.
These instruction do not refer to the gap at all.
The gap is 0.25mm (or 0.01") on both legs.
I hope this helps.
Mark


Not that it is important now that he has given me the correct gaps, but I'd still like to understand their instruction page. It's the only thing that came in the box with the module. There is nothing in the original manual. Does it make any sense to anyone?? It's clear as mud to me.

 

[Marc-Antoine]

It seems this spare module can be mounted on different cylinders ( I can't tell if it's the same model but different generations, different outer designs or different cylinder's capacities). The mounting points on the cylinder could be short or long (the "a" ref on the drawing) but the module has to be located at the proper place on the side of the flywheel. So you put or not the spacers between the cylinder's mounting points and the module.

The setting of the air gap is an other story, after you had put the module at the right position in relation with the flywheel's thickness.

 

[bstewert]

And the winner is, THE COIL.

I finally put it all back together yesterday, with all gaps at .025 (including the plug) and it fired up on the 2nd pull. It hasn't done that ever, even when brand new.

So thank you everyone for your imput and help.

Also wondering about the spark arrester (if there is one on this model). Is that something that should be checked or changed? Would a messed up one affect performance?

 

[Burnham]

If it has an arrestor, you ought to be able to see a screen or at least a mounting screw/bolt and a tab to pull said screen, at the exhaust outlet.