Stihl 026 dying after running fine for 5-10 mins

[bruiser1]

I also have an 026 get rid of that tank vent that's what's causing it I did and I didn't have any more problems

 

[johnbinsc]

Hi again experts!
I'm finally getting back to you with an update.

1) My spark plug is an Autolite 2984. The electrodes look good, with a light tan coating.

2) The rest of the wiring looks OK, although I did not take off the recoil starter cover thing to look at the wires all the way to the coil.

3) I did the spark test cold and hot by removing the plug and wrapping a bit of bare copper wire around the plug threads and the metal stud on top of the cylinder head. I saw a spark both cold and hot (i.e. after I couldn't restart the saw). My impression is that it is a pretty weak spark in both situations. For example, I could not see the spark unless I was in complete darkness. From other experiences I have had checking spark in the past (probably on cars), I'm thinking that I should be able to see the spark on the plug tip in shaded daylight, but I'm open to hearing your wisdom on this.

Thanks! --John

 

[Bob Hedgecutter]

Hi again experts!
I'm finally getting back to you with an update.

1) My spark plug is an Autolite 2984. The electrodes look good, with a light tan coating.

2) The rest of the wiring looks OK, although I did not take off the recoil starter cover thing to look at the wires all the way to the coil.

3) I did the spark test cold and hot by removing the plug and wrapping a bit of bare copper wire around the plug threads and the metal stud on top of the cylinder head. I saw a spark both cold and hot (i.e. after I couldn't restart the saw). My impression is that it is a pretty weak spark in both situations. For example, I could not see the spark unless I was in complete darkness. From other experiences I have had checking spark in the past (probably on cars), I'm thinking that I should be able to see the spark on the plug tip in shaded daylight, but I'm open to hearing your wisdom on this.

Thanks! --John

Not real familiar with Autolite plugs- I think if its a copper one it is R for resistor type and that is where you want to be.
Some coils (not sure if it applies to 026) cannot handle non resistor plugs and it cooks the coils. Which is why I asked the question.

 

[johnbinsc]

Several online listings indicate the Autolite 2984 as a copper core resistor,
and an online plug crossreference matches it to the NGK BPMR7A, which is what the parts list specifies as the OEM plug.
Online, one guy said the Autolite 2984 was the OEM plug in his Stihl 026.

So this might be the original spark plug.
I doubt it is bad, but it is easy and cheap to replace.

 

[Bjorn T]

You dont need a resistor plugg, I only use that on saws with m- tronic or Auto-tune. Try a new coil and a new plug without R. This is a good one.https://www.trodo.se/tandstift-denso-w22mp-u?utm_source=google&utm_medium=cpc&gad_source=1&gbraid=0AAAAADJzNp4ZhhhLhdYZo7xxFkRyvEzgu&gclid=EAIaIQobChMIkr65wIGqiAMVbE-RBR2l0B3REAQYAiABEgIHK_D_BwE

 

[alabamatriker]

Tank vent is very likely your problem. If you know about when it is going to quit, open the cap and close it back just before then. If it doesn't quit then, it is tank vent. I had 1 that would cut 6 blocks and quit. It would not start until next day. So cut 4 blocks and then while running turned it on side and opened fuel cap and the closed it back. Did that every 4 blocks for 2 tanks and it never quit. Replaced tank vent and it has been fine since.

 

[HumBurner]

Hi again experts,

I am a homeowner on a wooded lot who occasionally takes down his own trees.

My 30 year old Stihl 026 starts and runs great for 5-10 minutes.

Then it either dies on idle or I shut if off to do something, and when I go back to restart it, I cannot get it started.

But if I wait until the next day, I can get it to start easily and it runs for another 5-10 minutes.

It has had this problem for a while, so I did a carb rebuild, but it still has this problem.

I thought it might be vacuum lock on the gas tank, but I can remove the tank vent and then replace it and it still will not start.

So it seems to be related to the saw engine getting hot.

I saw one suggestion on another site that my gas line might be pinching off when it gets warm. It is the original gas line, and it is on my to-do list to replace it, but I have not yet.

What do you all think of that theory?

Is there anything else I should look at? What are the chances that the pulse line is failing when the saw gets hot (warm)? Of course, that is also the 30 year old original.

Thanks,
John

Check your grounds and wires thoroughly

I let go of an 056Mag because it seemed like a failing coil. Turned out to be a ground that wasnt keeping contact once heat caused expansion and it rattled around.

 

[johnbinsc]

Hi Experts,

Wanted to get back to you with the resolution to my problem.

I installed a new aftermarket coil (Partsrun brand from Amazon) in the saw and it seems to have solved the problem. I ran the saw hard for 10 minutes cutting up some fallen logs. I then shut it off, and was able to restart it easily back to idle with one pull of the starter cord, i.e. I didn't even have to lock the throttle at high throttle to get it to start back up.
I also got a new spark plug (NGK), but I did the spark view test with just the new plug and it was no better with the new plug than the old one. Then I changed out the coil and the spark view test showed a much brighter spark. I didn't check if I could see the spark in daylight with the new coil, but it was so much brighter I figured I had resolved the problem.

The saw runs so much better I need to go back through the idle and low/high mixture adjustments on the carb now.

Thanks again for all the very good suggestions about what might be causing the problem. All of them caused me to take a more critical look at many of the saws components and systems, and I learned a bunch.

--John