Help with Stihl FS 45 trimmer

[GBertolet]

I am repairing a Stihl FS 45 trimmer for my neighbor, and I am stuck. The machine was sitting for some time, before it was given to me. There was no spark, and the coil tested shorted. I replaced it for $10 , and now I have spark. There was no fuel coming to the cylinder, and I replaced the carb for $10 also. I now have fuel in the cylinder. I cleaned the spark arrester also. It was pretty clogged. At this point, I have frequent backfires through the muffler when attempting to start. Occasionally, I have blowback through the carb also. I checked the flywheel key. It was beat pretty bad, so as a precaution, I found a used flywheel in decent shape and replaced it for $20. Still won't start and backfires. I have heard that sometimes the electronics in a coil are bad, but still spark, but the timing is way off. In the Stihl manual, it mentions this possibility. This sounds like what I am experiencing. Do I have to just buy another coil to see if my suspicion is correct, or is there a test? The coil I have now was a cheap import. Maybe junk to begin with. Any suggestions would be appreciated.

 

[DND 9000]

It is possible that you have a coil with the wrong ignition timing. On aftermarket parts you never know if they are good or not. Please give us more specific information. Exact model of your trimmer, year of manufacture, serial number etc. What is written on your old oem ignition module? How is your piston looking, (inlet and outlet side)? You say you have spitback through the carb. A little bit is normal but not to much. A carb for $10 could be junk too.

 

[Fish]

Take off the muffler, then try it.
Take a look at the piston while it is off as well. The exhaust port may be carboned over.

 

[GBertolet]

Thank you for your responses. I had the muffler off already, in preparation for a vacuum/pressure test of the crankcase. No leaks. No carbon blockages on the port. The info on the old coil is Stihl 4140 1303A MA-43-1982. The kill terminal was shorted to the core. The tag on the trimmer lists 4140-011-2301, SN 255823942, FS 45 Z Stihl Trimmer, 045-1016. I can't find a date of manufacture.

 

[DND 9000]

A new oem ignition module for your FS 45-Z would be the 4140 400 1308. But if it fixes your problem?

 

[GBertolet]

I had just done some more research. The 4140-400-1308 coil is for post 2001 FS 45 trimmers, and is incompatible with 2001 and earlier 4140-1303A, coil FS 45 trimmers, which mine is. The new replacement coil I had purchased, is a 4140-400-1308. If this proves correct, this is my issue. I will have to look for one of those old obsolete coils.
https://www.greenacresmowers.com.au/ignition-coil-module-for-stihl-fs38-fs45-fs55-fc55

 

[Fish]

The date of your trimmer should be on the sticker, if that is still legible.

 

[Fish]

Here is a pic of the 2008 price list.

 

[Fish]

Here is out of the 2019 price list:


4140 400 1200 FLYWHEEL $69.58


4140 400 1304 IGNITION MODULE (MM55) $29.89

4140 400 1305 Ignition Module MA-54 $34.63

4140 400 1308 Ignition-module $29.89

4140 400 1309 Ignition module $40.20

 

[GBertolet]

I found a Stihl 400-1303A coil. Should be here by the end of the week. I will let you know.

 

[Wonkydonkey]

I can confirm the backfiring is down to the wrong coil. I had it with a fs55

 

[GBertolet]

Fixed! The 1303A coil did it. Popped the first pull and started on the second. It's frustrating on how secretive Stihl is on product maintenance information. In 2002 Stihl went to the 400-1308 coil. This makes mine, a pre 2002 model. It's just dumb luck, that I stumbled on a narrative for an aftermarket 400-1308 coil, that said don't use this for a replacement for a 400-1303A coil, as they are incompatable. The average person would not have known this, and ultimately out of frustration, thrown this trimmer in the trash heap. Wonkeydonkey nailed it though. Thank you.

 

[Wonkydonkey]

Yeh, I had the fun of buying the wrong one, and had the same prob backfiring.

The only reason I found out was I took/swapped it with another coil off some other trimmer.
Then I found the coils were different. Because the backfiring coil work on the other older trimmer

Your probs were really the same as mine... pleased you sorted it thou.

 

[geltam11]

Hi all,
i have the same issue. My Fs45 is a 2007 model, still has a 4140-1303a coil. With the aftermarket 1308 coil, it is just backfiring. I can't fint a 1303a coil. How much is the ignition timing difference?

 

[Wonkydonkey]

I think page 5 of the doc, that @Fish posted. shows the diff placement of the key way on the crankshafts....

It would obviously mean filing yer key out of the flywheel...which I would not want to do..

It may help studying the ipl and making sure you have the parts you think you have. As well as identifying the crank keyway position to the pic of page 5.

Anyhow it in post 7 above or here
http://opeforum.com/threads/help-with-stihl-fs-45-trimmer.17520/#post-916820

 

[geltam11]

I have the 1303A, i can't see that on the list. Is it the same as the 1303?
Or what is the replacement for it?

 

[geltam11]

I went to the Stihl shop, they said that the original 1308 will be okay for my FS45, the aftermarket one is just not good. Which is a little confusing for me, because the timing on the 1303A and the 1308 shouldn't be the same.

 

[Wonkydonkey]

I have the 1303A, i can't see that on the list. Is it the same as the 1303?
Or what is the replacement for it?

Yes, I think that’s correct.


If I recall correctly....... I brought a China coil for a fs55, this was about 3/4 yrs ago. at the time of me buying it, it was listed as it would fit my machine same part no, but it also listed another part number, which I don’t know/can’t remember...
We have 3 fs55's and some other makes.
I had fitted the new China coil to the faulty coiled fs55 it backfired, after scratching muh heed...and not much hair left because of me screaming f-ing words and scratching head and pulling hard.. ... on the rope
I got out the other two fs55. I dismantled each of them. And found the China coil worked on the newest fs55 (iirc, 2015 model) but would not work on the oldest model (irrc 2001) it backfired as well.
The 2001 model which had a working coil worked on the faulty coiled fs55

And after a few short vids to send to the eBay seller. I got my money back, but not before they tried to sell it for half price as a backup for the newest fs55.. of course I refused as I was buying a part that did not fit the machine it was supposed to...

So what I’m saying is, yes the stihl dealer is right, a 1308 coil should fit yours and yes the

China coil is not what is says it is.

.. find someone with a newer model and it will probably work. (Shame the China coils don’t get marked up with a number for reference)

Oh, and this is the long story of how I knew the backfiring was the wrong coil in the OP.

Btw... I even tried the China coil and also a stihl coil on another make trimmer, McCulloch or was it a jcb,? ( I will have to look) the stihl worked and the mcColloch/jcb coil worked on the oldest stihl fs55.. the only diff was a longer HT lead on the mcColloch/jcb.
The China coil did not work on the other trimmer (mcColloch/jcb).

Unfortunately you will have to buy a new stihl or secondhand coil.

 

[GBertolet]

I am the O.P. of this thread. I had to go to ebay to find a 1303A coil. I could find none anywhere else. And all I could find was a used coil from a parted out FS45. It was an original Stihl, and was guaranteed good, and it was. I paid $9 U.S. for it. Most lawn equiptment repair shops have a junk pile of power equiptment out back. Maybe you can visit the local shops and see what scrap Stihl equiptment they have in the pile. You might luck out.

 

[geltam11]

Now with the original 1308, it's working properly. Don't buy the chinese aftermarket one.