Stihl 038av ignition help

alexihc · Mar 9, 2015

Hello to you all, I got to this site with the help from my old IH tractor mates on a US tractor forum I post on .
I have a old 038 av electronic quickstop , so is tells me on the orange cover which is true as I know.
A old guy gave me this a few years ago , and after fitting some new vibration mounts and good tune up it has done me well for a few years now cutting firewood and felling a few small trees. I do have a smaller Husky saw also , but doesn't have the power this has.
Last time I used the saw a few months back the oiler was leaking, so this week I got to look at it only no able to start the saw , which was odd.
Turns out I have no spark checked plug , wiring , kill switch, cleaned faces and set the air gap etc. I think the coils gone bad, as with a multimeter I have full contact or dead short from the small primary wire to the body of the coil. I was expecting to see some resistance?
Took it to show 2 different Stihl repair shops and been told its to old and parts NLA . I done some e bay searches and find coils for later 38's and other saws all look different though.
Also what does the module do under the flywheel ? This is sealed and has 2 wires from one screw , one to the coil and one to the kill switch ? I have tried running the saw without the wire connected.
I can't find exact replacments for either part. Is there another later coil that will fit?
I am at a loss on this saw it runs great and has plenty of life left in it , shame to scrap.Looking at a few ms390's if need to replace , will this be as good as my old 038?
S/N on saw 8 513859
Coil Bosch 2 204 222 050
Module Bosch 1217 280 107

Oh better just say I am over in England , so may not be able to get hold of the same parts as you guys.

Thank you for any help or advice .

Alex.

hotshot · Mar 9, 2015

That's the old 1118 400 1000 module, I saw a used one for sale recently on US fleabay.

You can use the newer & smaller 1118 400 1001 chip (crappy cell phone pic attached below), and just mount it out from underneath of the flywheel, on the coil mounting bolt. The heat kills the transistor where it's mounted.

Those chips should still be available at your Stihl dealers for around $30.

Have you checked primary & secondary winding resistances on the coil yet? Better to cross that off first, but they rarely fail.

alexihc · Mar 10, 2015

Thanks for the info, so if I go to my local Stihl guy with 1118 400 1001 p/n he should be able to get one? Then I mount in outside of the flywheel in the space below the coil?

I did measure the primary winding as I said . Multimeter on the small wire to kill switch , the other wire on the small wire rivet to the main coil body , I get full continuity , the meter goes to 0.00 as in having a short or closed circuit.
If it was on a motorcycle for example I would expect to see a 50-100 ohms.. That what has lead me to think the coil is dead.

Oh also I looked again and stamped inside the flywheel looks to be a date stamp with 79 on it .

I ll go from here , thanks again.

hotshot · Mar 10, 2015

Kill switch in the ON or OPEN position (or the wire removed), then remove & isolate the wire ring terminal from the black donut.
If the kill switch is OFF, you'll get zero ohms like you read, because it grounds the circuit.

The primary side ohm reading from the coil body laminations to either of the above wire ends should be about 0.7 to 1.2 ohms. I'll look later for the ranges in the service manual, if I can find my copy. The secondary side should be about 7.7K to 10K (thousand) ohms, measured from spark plug lead end to the coil body/frame.

Zero your test leads out, or check that resistance first, to subtract the value out (if your meter does not have auto zero function)

alexihc · Mar 13, 2015

Good news , with thanks to some more reading through this forum I have my saw running .
I got another coil from a later 038 , I knew the bolt pattern was different , but could have been made to fit if it come to that. But did do some more Ohm measurements from it and came to the conculsion my coil was in fact ok , and the problem lay with the flywheel module.
After some looking I found the replacement condensor mod for sale over here in England. Ordered one through a e-bay seller for £11.00 , around $15 .
Simple mod , removed and threw the original module .. The cut the wiring from the coil just away from the coil, spliced the wire to the kill switch and the new wire to the little magic box. I soldered and slid heat shrink over the join to seal it up , re fitted the coil as spec , fixed the convert box on a coil bolt for a good earth, the with plug out resting on engine gave it a pull , good clean blue spark.
Built up rest of saw , started 2nd pull!
It feels and sounds alot crisper and really rocks in your hand when you blip the throttle. Ready for some timber now.
This is how I set it in the saw.

This is a pic of the saw, nothing to you guys , but has done me good service and his big enough for my work.

Just like to say thank you for the replys and the other threads I have read about on this forum.