Testing and replacing the ignition coil on a Stihl FS 80R string trimmer. In this video I do a few tests to determine the problem with my string trimmer, then show how to repair it.
Great video!!! Thanks for showing the alternative testing method for those who don't own the spark ignition tester---a totally save for me!! Also, I didn't know their is a gap requirement between the magnets,--much appreciated as it surely would have ground down part of the module. Clear and informative instruction for diagnosing my Ryobi RY34000 (x430)---I'm now a subscriber to your channel. ....Kudos
you just saved me all kinds of time, effort and money. I used to own a Mowing company that mowed and trimmed for the state of TX and the U.S. Corp of Engineers. Have worked on many of weed eaters . Retired now and have had a Stihl for about 7 years.. Only problem I have had is the gas filter in the tank, and the muffler screen, also build up in the exhaust port , that is until now, The plug has week fire and a new plug wouldn't fix it. Figured I should just buy a new one as the local guy charges 75 a hour to work on one with one hr min. I tore it apart and figured it was scrap. Thanks again.. I now have a nice running machine once again. apologize for the poor wording , kind of in a hurry. Drurry
drurry nuff'said That's great to hear that you are back up and running again. These machines will run for a long time with a little repair now and then. Thanks for watching.
Thanks for your informative video. After cleaning the carb and a few other parts I could not figure out why the starter cord wouldn't pull out. After watching your video I realized the ignition coil was too low and had to be raises slightly. Thank You!
When I was a pro motorcyle mechanic, we used to check for spark by sticking a pinky finger in the spark plug boot, ground your index finger on the case, turn on the ignition and crank over the engine. You know right quick if you have spark. That one always impressed the customer.
I think this video is very helpful. I also noticed a comment that you did not test the coil and this is because the coil also has an ignition module built inside and cannot be repaired. So if you have no spark you must replace the complete unit so it would be an unnecessary test to do and show. It would be a different situation if the electrics had a separate ignition module or even points and condensor, then you do need to test the coil.Good helpful video with clear and easy instructions on how to replace a dead coil unit.
It is still important for the fact of us that has a spark and or weak so that would be a waste of money to by a coil so a pin out reading will help to see if its "in spec". You fix stuff the proper way that way and you not a parts thrower on it but an actual mechanic.
Have a homelite trimmer that was running poorly ,had good spark,getting fuel, fuel lines were ok ,good filter tried cleaning carb, same issue.....even adjusted fuel mixture on carb ,same results, went on EBay bought China made carb new $10 ,put it on,runs like new.I did have to fine tune carb .these little engines are pretty simple to work on ,especially if you watch enough u tube videos, they really help.
This way looks very professional and systematic. I have no experience in small engines. But I enjoyed your video. I have a question (I don't know, may be its a silly question) How is the resistance of the faulty vs. good ignition coil ? Can we check them using a ohm meter ? Have you ever tried ? Thanks.
Not a bad video at all. Much better than one I saw a while ago where he just stuck it on and didn't think the spacing or much else since it looked like he contaminated the crankcase to get to the coil which in his opinion was easier but after using it again less than 15 minutes after turning off the camera I wouldn't be suprised if the thing failed and was tore up inside lacking compression or seized maybe.
Response to L Bandara Due to your security settings I could not respond directly to your comment. I am not sure of the resistance of the coil but I'm sure there would be a difference between a new one and one that is no good.
I found a much better way to test the coil. Take a nail and wrap a copper wire around the one end of the nail. Then put the nail in the spark plug cap and give the other end of the wire to a friend who is helping you out but knows nothing about engines. Tell him or her to hold down the engine with their other hand and give the rope a pull. If the friend jumps and starts yelling the coil is good. If not then you know its bad.
I was reading a booklet actually from the company that made his trimmer and a 75 which is similar also that says the spark should be able to jump a 8mm gap during cranking speed if its a good well functioning coil.
How can it start if the stop switch is disconnected? Does the stop switch short to ground to prevent a spark in the cylinder? That would work but it's not "fail safe" and I would think it's designed some other way.
If use your meter on ohms, go from the arm that goes thru the center of the coil (core)or the arm that goes toward the magnet. Then the other lead goes to the spade connection coming out of coil, you should see no ohms or an open. If you read anything between these two points then the coil is shorted to ground which is the same as having the switch off. Which the switch actually shorts the coil or ignition module to ground.
funbro, thanks for response,,, if I remove switch and connect wires dose this ground or open the coil for ignition ? (jump switch) wired from one coil post to other?
Great video. I do have spark to the spark plug. I have taken the carburator off and cleaned thoroughly. Fuel filter appears great. I am not firing at all. But some fuel is misting out of exhaust. Still wondering if the spark is weak and still may be a bad coil??
+Cullen Haskins If the spark is weak that may be the issue. When I replaced mine it started out getting weak then went bad real quick. The guy at the repair shop said it was good but when I installed a new coil it fired right up just like new and has been running great ever since. Hope this helps, Thanks for watching.
Great video, thanks Bob. My twenty year old Jonsered GR36 brushcutter won't start. Coils for it are no longer available so I wondered whether I could use a coil from a different machine. Any ideas please?
Hi, thanks for your reply. Yes, you may be right and the Chinese ones are so cheap now it may not be worth bothering with the Jonsered. All the same, if I can find an old coil I might try it as it was a good machine. If it works I'll let you know
Quite so, that's what I thought. I've just bought a spark tester to be sure that the problem is the coil. If it is I'll try to find a coil that fits and if it works will let you know. I haven't used the machine that much, it's just old in years, but it was good. Thanks again, John
I have a trimmer that only sparks one single time on each pull, could it be the ignition coil too or another issue? The coil isn't completely dead but just gives a single spark.
I need an ignition coil for a Stihl BG55 blower. I'd like to get an OEM part. Where can I buy it? Can't find the Stihl part number online. Thanks for posting this excellent video!
I have KM90R and iprocess of removing coil I lost one of the spacer washers between coil and engine. The other one appears to be ceramic and wondering if I can replace with a couple metal washers for same thickness or try to find the ceramic ones? It doesn't appear that yours had these? I've searched work area and it just disappeared??? @$%$@ Got new coil installed and still won't start so will do the tests you showed. Also have to remove handle to fix top switch that lost it's spring in the process. Hopefully is an easy fix ! New wire came with coil and may have to switch out wire?
If you have spark make sure the fuel is getting through correctly. That and the air/fuel mixture is all there is to it. What about compression? Does the piston create compression?
My sister’s Stihl Fs 90 only using less than 20 hours,the coil go bad,replace with one China made ,(16 $ , ),start up the first pull, the old coil resistant have (1450 ohm ),the new coil measures at 2580ohm, ??? Does anyone out there have coil went bad so quickly of same model fs 90, I assume it because the heat,causing the problem, I have done some modified , hopefully it can help made the coil live longer . My ryobi 2011 old coil go bad measured at 1, 2 m ohm , replace new coil measures 7, 6 k ohm
It's a simple setup on these things and thru a process of elimination you can determine what part isn't working with a fairly high level of confidence.
Mine is a Husqvarna 322c and it has weak spark, its even hard to see it jump spark plug gap. I actually put a screw driver in the plug boot and held the cylinder and cranked it, i feel a tingle but its not enough to make me jump. maybe this is why when it runs it runs so bad.
Sir, My BG55 Blower needs a new ING Coil also. I bought a new one at Ace and it's A Stahl also! How ever the rear Small wire terminal plug came off the old one and there is not one "wire terminal" on new coil. So my question is does the wire terminal get mounted on the new one and if so how?? Thanks any help anyone can be..
how long b4 your coil failed??? I have an FS80; it's been having issues lately starting; used to always be a one or two crank TOPS startup now it also could be flooding issue too; i saw how to clear out a flooding issue and it takes me about 25-50 cranks and really sukks.... how much is an ignition coil??
funbro1 ROGER. Ill have to test mine with your method; takes about a million cranks now to get it going. used to be a one-two puller. thx. it's a badass trimmer still tho and i'm not going to quit it. one of the last great two strokes 🤘🏻
I love it when people don’t talk shit. Thank you great video. Maybe you can teach some of these clowns how to make and informative video that pertains only to the object that their fixing. Thanks again video helped out a lot it was exactly that.
My Stihl mechanic said my timing might have slipped and altered timing. What did he mean? My understanding is that the coil is preset and cannot be altered. Was he talking about the magnets position on the crankshaft?
If the key on the flywheel slipped or broke, it can make the flywheel magnets move out of timing vs the cylinder position, The key is what holds the flywheel to the crankshaft
+Hillis Mowing & Lawncare I'm not sure if they are the same but a quick call to the dealer or an internet search will tell you more. Either way the testing should be the same, any disassembly may be slightly different. Hope this helps, Thanks for watching.
I'm missing the upper screw on my SF74 trimmer ignition coil. Can I use a generic screw here, can I buy a single replacement screw, or do I have to buy a whole new coil? The coil seems to be working, but due to the missing screw it has shifted position, so all I need is the screw.
@@funbro1 Thanks. My local Stihl dealer gave one to me. Along with a fuel line replacement I'm so happy my awesome ancient SF74 is working again! Any replacement trimmer would have cost $350. It has the high quality tap type head and cuts through most anything like a laser. I also don't use the heavy line-cutter/guard thing because I know how to keep the line at the right length and it adds weight as well as blocking the ability to get around in tight spaces. It's a dream to use once again!
I have a FS80 and can not get it to fire,, if you connect the wires at the coil that goes to switch(if switch is bad)they will be direct from one post of coil to the other,, will this cause a ground or will it by pass the bad switch? I've done every thing, jumped switch as stated, replaced coil, still no fire ???? any suggestions ?
Sounds like it may have grounded and since you have already changed the coil I would be leaning towards the switch. You can test the switch by setting you meter to Ohms. If that is not the issue then there must be a broken wire somewhere. Hope this helps.Thanks for watching.
can a person just do away with the switch and tie the two wires together and make the trimmer run or have spark ? FS80R Stihl trimmer,, was running perfect, put it up, when I went to use it the next time has not fired since,, tested the coil by passed the switch as said, switch coils , good plug,, can not get this thing to fire,, any suggestions ?
Can anybody help? I've got a mountfield model 23 brush cutter that had no coil, I found a replacement coil ... but I've got no clue where the positive and negative cables from the hand controls go, or where the black cable from behind the fly wheel connects to ... It would be nice to get her hooked up so I can whack some weeds! Thanks to anybody that can give me some advice. 😁
hava a question if you can answer i will presiate i have an echo weed eater works good for like 10 minutes when gets hot it bog down i replace the carburator line fluid and spark plug an it still doing the same did you now what it is
I was told years ago by a knowledgeable, Stihl mechanic that a chain saw I was using was having vapor lock. When I asked him how to prevent this he said to use the best possible fuel ie Premium. This seemed to work for me Try it and see if you have any luck. Hope this helps. Thanks for watching.
LividLeon Any authorized Stihl dealer should either have the part or be able to get the part for you. What city do you live in? You could also check on eBay if you don't need the part right away.
i got a Honda gx35 4 stroke grass trimmer and every time i start it @ first 5 mins it runs ok... but when it starts to warm up it begins sound like its been choke or something....runs sluggish ..tried to rev it and it dies immediately.. test the ignition coil.. and it tells infinite numbers which worries me ... is that mean i have a faulty ignition coil?
Min Es If it starts right back up but doesn't rev then I would say that you are looking at something wrong with the carb. If it doesn't start back up then the coil might be the next place to look. Hope this helps. Thanks for watching.
wont start after ... when it cools down a bit starts smooth then it gets rough again .. i did some experiment thou .. using my hand drill then a device just like yours checking for sparks.. and saw the sparks is not constant.. breaks randomly.. test the ohms and it goess really go down from 6k ohms to .7ohms.. so i guess 100% i got a faulty ignition module
One more question. The sparkplug came with this trimmer has 20 ohms (rather too high, I think) and ignition's secondary coil has 3000 Ohms. Need I replace sparkplug? What do you think? Please, let me know!
Seems alot of 2 stroke engine coils go bad internally. Anyone know why? I bought a small King generator--one 10 minute use and no spark. $40 dollars USA is alot for a machine that is worth $100 dollars new. By the way--rust build up between the coil forks and the magnets could be a problem. However great presentation and professional done. Thanks :^)
Not scrutiny brother but first before all is to check the idle screw, play with it, also check the choke some engines like richer, rich and lean “more fuel on initial combustion. Check spark plug and switch, then,,,, magneto. Also? Does it have old gas in it?or is it two stroke and oil/ gas mixture correct? Is there water in the gas tank from sitting for awhile, due to condensation?
hi...i have the same weed eater. it only runs for about 30m and then shuts off and it wont not start again untill is cold..i already change the coil, the spark plug, tha carb. any ideas?
Check spark plug gap cold and hot to see if it’s changing. From the manual here are the specs: Spark plug (suppressed):Bosch WSR 6 F, NGK BPMR 7 A or Champion RCJ 6Y Electrode gap:0.02 in (0.5 mm). Also, never assume a new part is good if problem still not resolved - test new part if not sure. Hope this helps - please let me know. 👍🔧🧰
I was told by a Stihl mechanic, when a chainsaw I had was doing the very same thing, that these should only be run with premium fuel. I don’t know if you’re running premium fuel or not but if not try switching over to that it seemed to solve that problem for me. Hope this helps, thanks for watching.
Question, I have an old FS-85 (20+) My "off switch" does not have the blue wire, just the black wire. I pulled the spark plug and tested it, I am getting a spark. I rebuild the carburetor but the engine will not start. There is fuel on the spark plug. I am totally stumped. I was a marine mechanic at one time. I know these engines are not complicated. Could the coil be intermittent? I have checked the throttle linkage, coil, and carburetor even ordered a new carburetor. Still no joy.
Have you removed the spark plug and grounded it to see if you are actually getting spark where it needs to go? Other than that I think you covered most everything else.
Yes, I removed the spark plug installed a new plug and check the switch it was good, then I used a spark plug tester and had a good spark. I got the trimmer started, it ran and ran, then I let it set a while and it will not start. New fuel lines new primer bulb. I am baffled. But thanks for your advice.
Check the fuel, I once had problems with my Stihl chain saw where it would run real good then when I went to refuel it it would barely run iof at all. I was told by a Stihl mechanic that I was using old or low grade fuel. I switched to premium and never had the problem again. Just another possibility???
Thanks for the reply, but I went to the store and purchased the premixed high-grade fuel in a can. It will start run about 30 seconds and stop. I wonder if I have a bad coil, I check the spark plug with a tester and it shows a spark. I wonder if the coil gets hot and quits. I did check it with an ohms tester and it shows no resistance.
Replaced the module last season on mine. This spring I got a couple pops out of it, and no spark. Couldn't believe it. Anybody else seeing this? Another module was the fix.
Replace a new coil with a new plug last year, the Fs 90 running great, last week 06/06 /20 , it’s stalled after 15 minutes, check the plug, it went bad ( 6 m ohm), replace new plug , it run again. ? ? ? A new plug total running time less than 7 hours ! ? ? ?
john Wow If use your meter on ohms, go from the arm that goes thru the center of the coil (core)or the arm that goes toward the magnet. Then the other lead goes to the spade connection coming out of coil, you should see no ohms or an open. If you read anything between these two points then the coil is shorted to ground which is the same as having the switch off. Which the switch actually shorts the coil or ignition module to ground.
Worse if your engine sort of runs ok but shuts down after 10-20 mins hot and fuel system is ok?? Drove me crazy till i realized the coil was de- laminating and shorting when HOT! I guess to test you could put a hair dryer on the coil and watch the resistance go down a bit? and then suddenly short out!!
