SUCCESS!!! Just repaired Stihl 045/056 Bosch electronic ignition!!!!!

[Mike D]

Here is the number for Mouser Electronics Capacitor. Vishay part #594-2222-378-52105 series 378 mkp. This is 1uf pulse rated @ $2.89. mobile_bob that is the replacement for a points system.

 

[Mike D]

hotshot can you tell me how you you check the timing on the flywheel side.

 

[hotshot]

hotshot can you tell me how you check the timing on the flywheel side.

Mike, it's a royal PITA but here's how I do it on the 045/056 saws. Get another person to help, because you'll need three hands. Watch your fingers around the fins when you're spinning it, as you have to hold the saw down and run the timing light and run a drill or air tool all at the same time...

Start by finding TDC with a piston stop & mark the flywheel and case for TDC, anywhere convenient. Move the FW slowly back and forth, make a light mark at both the stops, and the TDC is exactly in between. I use white chalk on the FW, so the marks are probably 2° wide or more...but I can see it. Back the FW off (CW) 26° with a mounted degree wheel, and then mark the case again for the 26° BTDC point, using the one mark on the FW. You can also print a reduced size degree wheel off on paper, then cut it out & center it over the FW nut to get really close. Tape it down on the sides to get to your 26° BTDC mark, then tear it off.

Get a timing light and hook it up to a 12V battery and the saws spark plug wire. Pull the plug, ground it (I use a clip on spark tester), then turn the kill switch ON. Make sure the choke is OFF too.

Take a drill and spin the FW nut CCW at the drills top speed (drill put in reverse) and then check the FW & 26° marks alignments with the timing light. Remember to torque the FW nut down hard before, or you will just spin it off.

If the FW mark is showing/strobing below (before) the 26° case mark then you are advanced, and if it's above (after) it you are retarded. Adjustments are like most Chevy distributors, so loosen the screws and barely move the stator CW to advance, or CCW to retard it. The later timing lights have a degree dial on the back, but mine is old school. Mark the stator plate edge and the case with a punch when you get it set, so you can put it right back if you take the coil off later.

Stihl service manual states that the saw should be running at 6000 RPM or better, but these old ignitions have no auto advance features. They also check it on the clutch side with a bar stud mounted fixture, but you're going to be popping the flywheel off & on for final adjusting, so why not have the starter cover already off?

Technically, there will be less of a delay on sparking the faster the saw runs, but using a drill has always been accurate.

 

[mobile_bob]

Here is the number for Mouser Electronics Capacitor. Vishay part #594-2222-378-52105 series 378 mkp. This is 1uf pulse rated @ $2.89. mobile_bob that is the replacement for a points system.

thanks Mike D. my german isn't so gut! i figured out it was for the point system a few hours after posting.

 

[mobile_bob]

well i finally took the time to take this saw down, and the insides look like they just came off the assembly line, squeaky clean, bright and shiny under the flywheel. i did note the kill switch wire insulation failing so i just clipped it off and reassembled, just to check for sure that was not the problem.... it wasn't.

after determining the unit is actually a bosch cdi and not a SEC (i am not a saw tech and have never seen either) i did two things.

first i went ahead and ordered the replacement from the german ebay seller, the one made to replace the bosch/ducati cdi unit. figured i would have it in the next couple weeks or so.

second i found a source for the 1mf 400volt polypropylene pulse rated capacitors, and placed an order, should have 10 of them next week sometime.

while i am waiting for the german aftermarket part to arrive, i will go the repair route on the original unit, and see how it works out... if it works out i guess i will just put the replacement on the shelf for the day the original goes out.

we all know how that works! if you have a replacement on the shelf the original no matter how patched up it may be will run forever.

i really like the saw, especially after finding out the original owner only used it to cut down about 20 tree's over a 25year period. it was used as a felling saw and he did all the limbing with a smaller saw. he told me he thought he would use it on larger tree's but really had very little use for it after he bought it, it spent almost all its time under his bench in the shop. the second owner didn't have it long and used it to clear some tree's after a flood, and very little else.

so i am thinking it will probably last me for the rest of my life, for what i have in mind for it, that is if i can get the spark back reliably.

bob g

 

[Daniel Latner]

View attachment 348024


I forgot to show how the ignition looks and how I ran the wires. ALSO--- I FORGOT TO MENTION THAT HOLE YOU DUG OUT OF THE POTTING, FILL IT WITH EPOXY OR YOUR CAULKING STUFF. And be sure that yellow wire is tight and not loose where it can hit the flywheel.

Again-- best of luck----


Foggy

Any help on setting the timing on my 45 Super? I followed your instructions on this fix, and can't get my saw to crank. Have spark (felt with finger) but no fire. I have good fuel. I don't know where to begin on adjusting the assembly. Getting tired of tearing the thing apart every time it doesn't work.

 

[foggysail]

Hotshot has posted how to time these saws, I avoided timing mine because it was a BPITA job. I just set the ignition assembly to the mid point and things seem OK. The first setting I made I had the timing too retarded. Saw ran for awhile and then back fired through the carburetor along with blowing off the muffler.

If you have the capacitor fix behind you, MAKE SURE the shut down wire has insulation on it or it can/will short and prevent starting. I cut mine off. Also the crappy switch used for shut down has a high failure rate. Mine failed open meaning it will not shut off the engine, possible I guess they can fail shut which will kill the spark. I use the choke to shut my saw down.

 

[mobile_bob]

ok, coming back on topic...

i ordered 10 capacitors off ebay, and received a bag of china's finest.

i think i will go ahead and do the repair to the oem bosch ignition module
and put it back in. just to see how this repair works.

then i will have the aftermarket unit on the shelf as a backup.

bob g

 

[Daniel Latner]

Mike, it's a royal PITA but here's how I do it on the 045/056 saws. Get another person to help, because you'll need three hands. Watch your fingers around the fins when you're spinning it, as you have to hold the saw down and run the timing light and run a drill or air tool all at the same time...

Start by finding TDC with a piston stop & mark the flywheel and case for TDC, anywhere convenient. Move the FW slowly back and forth, make a light mark at both the stops, and the TDC is exactly in between. I use white chalk on the FW, so the marks are probably 2° wide or more...but I can see it. Back the FW off (CW) 26° with a mounted degree wheel, and then mark the case again for the 26° BTDC point, using the one mark on the FW. You can also print a reduced size degree wheel off on paper, then cut it out & center it over the FW nut to get really close. Tape it down on the sides to get to your 26° BTDC mark, then tear it off.

Get a timing light and hook it up to a 12V battery and the saws spark plug wire. Pull the plug, ground it (I use a clip on spark tester), then turn the kill switch ON. Make sure the choke is OFF too.

Take a drill and spin the FW nut CCW at the drills top speed (drill put in reverse) and then check the FW & 26° marks alignments with the timing light. Remember to torque the FW nut down hard before, or you will just spin it off.

If the FW mark is showing/strobing below (before) the 26° case mark then you are advanced, and if it's above (after) it you are retarded. Adjustments are like most Chevy distributors, so loosen the screws and barely move the stator CW to advance, or CCW to retard it. The later timing lights have a degree dial on the back, but mine is old school. Mark the stator plate edge and the case with a punch when you get it set, so you can put it right back if you take the coil off later.

Stihl service manual states that the saw should be running at 6000 RPM or better, but these old ignitions have no auto advance features. They also check it on the clutch side with a bar stud mounted fixture, but you're going to be popping the flywheel off & on for final adjusting, so why not have the starter cover already off?

Technically, there will be less of a delay on sparking the faster the saw runs, but using a drill has always been accurate.

The specs I have say 2.7mm(0.108 in.) before TDC. Is that the same as 26 degrees? I finished timing my saw, and still no fire. Have good fuel, and have no bad ground wire. Maybe my coil isn't putting out enough spark? How much should it put out?

 

[Daniel Latner]

Hotshot has posted how to time these saws, I avoided timing mine because it was a BPITA job. I just set the ignition assembly to the mid point and things seem OK. The first setting I made I had the timing too retarded. Saw ran for awhile and then back fired through the carburetor along with blowing off the muffler.

If you have the capacitor fix behind you, MAKE SURE the shut down wire has insulation on it or it can/will short and prevent starting. I cut mine off. Also the crappy switch used for shut down has a high failure rate. Mine failed open meaning it will not shut off the engine, possible I guess they can fail shut which will kill the spark. I use the choke to shut my saw down.

I'm not getting enough spark to fire my saw. I used Hotshot's method on the timing, and had enough spark to run my timing light. Put everything back together and can't see any spark on my plug. My bosch unit has "2 204 211 040" stamped on the coil. Is the coil possibly the problem? I have a spare on hand, is there a good way to test the spare to possibly replace the one on my saw with?

 

[foggysail]

Yes--- I saw a post on EBay by somebody who guaranteed to repair modules that are sent to him----$100! Much less expensive to follow the mod which at most will cost less than $5.

 

[foggysail]

Dan--

Tell us about your capacitor. What is marked on it and where did you get it from. As to the coil (high voltage pulse transformer) itself failing..... anything can fail. But the big 'but' here is the common failure is the capacitor. If you did everything as described here in the thread including using the capacitor or a suitable type and value, your ignition should work.

Did you cut off the wire dedicated for the shut down switch?

And as to testing..... I highly recommend NOT securing the flywheel other than tightening the holding nut just enough to pull the starter rope with the plug removed. And a silly question.....is the flywheel half moon key (I forgot the correct name for the thing) in place? After you get a strong spark, then and only then should you sock the thing together.

Also make sure the spark plug wire fits properly into the coil. In general, check your workmanship. To my knowledge yours is the first not to get up and go after the fix

 

[Daniel Latner]

Dan--

Tell us about your capacitor. What is marked on it and where did you get it from. As to the coil (high voltage pulse transformer) itself failing..... anything can fail. But the big 'but' here is the common failure is the capacitor. If you did everything as described here in the thread including using the capacitor or a suitable type and value, your ignition should work.

Did you cut off the wire dedicated for the shut down switch?

And as to testing..... I highly recommend NOT securing the flywheel other than tightening the holding nut just enough to pull the starter rope with the plug removed. And a silly question.....is the flywheel half moon key (I forgot the correct name for the thing) in place? After you get a strong spark, then and only then should you sock the thing together.

Also make sure the spark plug wire fits properly into the coil. In general, check your workmanship. To my knowledge yours is the first not to get up and go after the fix

My capacitor http://www.ebay.com/itm/111284585730?_trksid=p2059210.m2749.l2649&ssPageName=STRK:MEBIDX:IT it's hard to read the markings but this is what it looks like: 47n J 630v 378 MKP/MKP on the side it says BC HQ 0026

Here is the description from the seller on ebay:
2pcs BFC237864473 MKP 378 AC Pulse Film Poly Cap 0.047UF 630VDC 47nF Radial P15

I cut off the kill switch wire. But I think, now that I've reviewed the print on the cap, maybe that is my problem.

 

[foggysail]

Dan--

Did you read thoroughly how to install and what is needed for the fix?????


Your capacitor is a 0.047ufarad! A 1 ufarad or close that value is needed. YOU PURCHASED THE WRONG CAPACITOR!

Send a PM to me with your address. I will send a proper capacitor to you. And FOLLOW the modification directions!

 

[Daniel Latner]

Dan--

Did you read thoroughly how to install and what is needed for the fix?????


Your capacitor is a 0.047ufarad! A 1 ufarad or close that value is needed. YOU PURCHASED THE WRONG CAPACITOR!

Send a PM to me with your address. I will send a proper capacitor to you. And FOLLOW the modification directions!

Just installed the right capacitor, and fired right up! I need to wait until everything dries before I can work the saw. Sounds good though. Thanks again!

 

[hotshot]

Good job! You would have been just fine if you had stacked up 22 of those caps in parallel!

Yes 2.7mm or 0.108" is the piston top displacement position for the points setting at 26* BTDC, but on an electronic ignition you have to set it while running, or dynamically, not static like old school breaker points.

Your coil part number is the correct one, and it probably kicks out 15 kV if you could measure it at top speed.

 

[foggysail]

Good job! You would have been just fine if you had stacked up 22 of those caps in parallel!

.

HOTSHOT!!!

I JUST DID A BELLY ROLL while reading your post! I just gave you an "attaboy"

Foggy

 

[hotshot]

HOTSHOT!!!

I JUST DID A BELLY ROLL while reading your post! I just gave you an "attaboy"

Foggy

I know that remark wasn't very nice, but it's true!

I do have a question though. Can you measure high voltage coil output with an O'scope? I have an old TI scope from the 70s, but I don't think it's capable of isolating that much voltage.

 

[foggysail]

Yes-- used to do it all the time when I was a design engineer developing high power radar transmitters while working at a large company in Massachusetts. Not sure about your scope though but give it a try. There were two ways we used back then. First was a high voltage scope probe made by Tektronix that could ONLY be used for pulse measurements. If you tried to use it on high voltage DC or AC, the internal resistor divider would heat up and fail.

The second used a capacitor divider that we made for lab use. It was a sophisticated device needed to tune out the effects of the distributed capacitance.

If you hold your scope probe close to the high voltage wire (spark plug wire) you will see the voltage pulse. Try taping it so it will stay in one place while you change the saw's RPM. You will not be able to tell how high the voltage is but you will be able to see if it changes as the RPMs change.

Foggy

 

[JohnE]

This is fantastic stuff . Informative and useful, the next time one of my 056'es lies down I may have a go myself. The last time it cost £100 gbp and the guys at the local dealership said I was very lucky they had an ignition as the saw was a Canadian model and had a different set up than the European ones.
Thanks to foggy sail and you other contributors this is why I signed up to this forum smashing stuff . J