I am trying to get my Stihl 031 av running right. I bought this saw 43 years ago this month. I used it a few weeks ago, hard to start, but would run fine when it started. Went to use it again, and would not fire. Tore it down and found burned points. Replaced points with NOS stihl contacts. Replaced condenser with WIMA capacitor. Saw fired right up, but would not rev unless throttle was feathered, then would run WOT. Trouble idling. Changed to a different carburetor same thing, only worse. I guessed it might be timing. Bought a Stihl shop repair manual and read procedure for timing 031 av. Checked with two Stihl dealers, neither had tools to time engine. I bought another flywheel and cut the center out so I would have a setting cam. Got a static timing light and I had a dial indicator. So I moved piston to TDC by dial, turn crank in reverse until I had a dial reading of 2.1/2.2mm BTDC. Adjusted points until static light just starts to light in this position. Points are fully open @ TDC. Put flywhell back on ,set air gap to 0.2 with Stihl gap gauge and put saw back together. Saw does the same thing it did before I readjusted points/timing. I am at a total loss. I have been considering a module and bypassing the points. I see some people have good luck with them, some not. I hate to cut wires and not get a fix. Compression is 120 psig and coil checks within tolerance with Fluke meter. What am I missing.
Help with Stihl 031 av
- Thread starter hiraganna
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Set points @ .016
Right now they are at .015/.016. If I open the points up some more that will advance the timing. Does it sound like an ignition problem to you?
What has been your experience with modules. At 70, I like to have something to tinker with, this gives me no pleasure.
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Back in the day, the points and cond. were still easy to get. There was a difference between the modules that worked on the 032 models, but I never explored that, I just found that the Oregon trigger module worked fine on the 032, I think that the 031 had a timing problem with it though. So I never got too bold with advice on the 031.
Thanks for your comments. I am just afraid of the module. I will open the point gap tomorrow and see if that changes anything. I am getting pretty good at tearing this thing apart. I will let you know.
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So your flywheels did not have the plastic windows?
Yes the flywheel does have the plastic windows. I just took them out. When the saw is @TDC you can not see the points.
That was the reason that I made the cam tool from an old flywheel. If I get my head at the right angle I can see that the points are not fully open @TDC as they are currently set. If I turn the flywheel past TDC then they open up to .015/.016. If I am correct, then the saw timing is currently retarded. Too little gap retards/Too much gap advances.
If you decide to use a points eliminator on the 031 remember that you have to remove the flywheel key and advance the flywheel about an inch, measured at the outer edge of the flywheel. The Oregon chip works good on these saws. I've also used the Nova II on these with good results. Depending on where you mount it you may have to run a wire from the airbox to the main engine chassis to ground it..
If you’re having to feather the throttle to get the saw up to speed & it’s hard to start, I would suspect that the rubber bits on that 43 year old saw have issues.
I’d inspect the fuel line, impulse line, intake boot & seals for any cracks.
You can chase your tail for hours between the carb & ignition, and then it turns out to be a pin hole or crack in the rubbers somewhere...lol.
Points are just a maintenance item that need routinely cleaned & adjusted. Capacitors commonly fail on those 031 & 032 series saws, pitting the contacts. A quick check with a cap tester will show if it’s shorted or open.
Was the new Wima that you installed a 0.2 microfarad/400 volt MKP capacitor?
I’d inspect the fuel line, impulse line, intake boot & seals for any cracks.
You can chase your tail for hours between the carb & ignition, and then it turns out to be a pin hole or crack in the rubbers somewhere...lol.
Points are just a maintenance item that need routinely cleaned & adjusted. Capacitors commonly fail on those 031 & 032 series saws, pitting the contacts. A quick check with a cap tester will show if it’s shorted or open.
Was the new Wima that you installed a 0.2 microfarad/400 volt MKP capacitor?
Fuel system related.
De points @ .016. Put the saw back together and it would not fire, at all.
I had no spark. Tore it back apart, checked switch,etc. . Decided to check coil with Fluke meter.
The primary winding reading was within range, but the secondary winding was out of spec.Took coil to local Stihl dealer
I had no spark. Tore it back apart, checked switch,etc. . Decided to check coil with Fluke meter.
The primary winding reading was within range, but the secondary winding was out of spec.Took coil to local Stihl dealer
Update on Stihl 031 AV. Reset the contact points to .016. Put saw back together and it had no fire. I tore it back apart and checked switch,etc. Checked the coil again with Fluke meter. Primary winding was within spec, secondary winding was out of spec. Took coil to local Stihl dealer, technician was gone until Monday. The owner said that he did not think they could test my coil because it was so old. Can that be true?/ Saws still have coils, don't they /
Testing coils is really a waste of time, its not a positive result type of test that will guarantee a coil will work properly. Newer saws do not use the same type of coil older points saws used. The new electronic coils used are fired by an electronic chip that is potted in with the coil, this chip is what commonly fails on these new units that are referred to as a module. Running a test on a module gives a false positive result as well so in my years of doing this work I have abandoned testing coil and modules, not worth the time or hassle, just replace it with a new or known good used one and get on with running the saw is my advice.
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Look closely at your wiring, you will likely find the circuit too close to "ground" somewhere, which will "ground" out the spark, and cause your trouble. Put up some pics for us old pharts.
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Putting up pics here is very easy to do!
I would gladly put up some pictures if I had not already torn the saw down yet again. I have removed the coil from the saw and clipped the wire from the WIMA capacitor to the switch.
Nothing to see but parts. You may be on to something concerning "too close to ground". At one time today after having no spark, I was moving and repositioning the capacitor wire and the switch wire, cranked it over and I had a very weak spark. Put fan housing back on and got no spark again. Tried turning it over with drill, slowly, nothing. Right now, I am just taking a break. I thank everyone for their help. I will be back when I have a solution.
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Pics anyway!!
I'll differ from some members on this: With coil disconnected on both ends I check the coil with an ohmmeter from ground to points wire, usually just a few ohms, typicall 10 or less and from ground to tip of spark plug wire should be several thousand ohms, typically 10k or more. A lot of those saws with old wires will have a short in the kill switch wire to the surrounding metal. Might be good to get some shrink tubing and cover that wire from coil to kill switch..check the switch also. These saws have a very simple ignition system but when old the parts often fail. I've used the WIMA capacitors successfully on these older Stihl saws. The WIMAs I use are .22uf, 630v, 5%, 15mm pitch (distance between terminals.)
I installed a WIMA capacitor and had great spark. Saw fired right up, just would not rev. Today I reset points, ignition was retarded. Put saw back together, would not start. The only thing different done was point adjustment. Checked for spark and had none. Opened the saw back up, saw nothing wrong, played with the ground on the wima . Turned engine over and had spark, weak, but spark. I checked coil with digital fluke, the reading from primary was 1.0 ohm, withing spec (0.7-1.0) and checked the secondary directly from screw terminal on coil to ground and it read 7.03, spec is 7.7 - 10.3. So ,I am assuming coil is not good. Do you know anyone that has used the Ebay guy that's claims to rebuild these coils and installs a module with correct timing ? Considering giving him a try. My wife offered to buy me a new saw, what is the sense in that when you know you have an antique that can be made to run.
I will get you some pics. Have to charge up my camera battery. I do not own a cell phone. Call me old fashioned or stupid,
just never had a need for one. Where I live in the mountains of Va., there is no cell phone service here.
What ohms setting did you have your meter set at? Typically the secondary should be in the thousands. Measure from gnd. to tip of sparkplug wire with everything disconnected. Connecting the points or condenser will screw up the readings on the primary side. You indeed do adjust the timing when you adjust the spacing of the points, the wider the spacing the earlier the spark.
