Stale fuel issues

[guym3]

Can I share my experience and see if anybody else has found the same?
I've got a lot of Stihl chainsaws and some start a lot easier than others.
I often have trouble getting my ported MS261 to start but it runs fine after that.
Recently I spent ages in the woods and gave up, using another saw.

I'd always assumed that if one of my saws was running fine on a particular fuel then I could put the same fuel in the 261 and it should run. NO!!

I've realised that if it has had fresh fuel sitting in it for even a couple of days, then it won't start. Today it did that. I put fresh fuel in it and it started straight away.
The "stale" 2 day old (left in the chainsaw tank) fuel however started instantly in my 500i.

Can anybody explain, or comment on their experience, why some chainsaws seem much more picky about what fuel they'll run with. My 500i and 044 seems to run on anything however ancient.

 

[Hinerman]

2 day old fuel is not stale. It does not sound like a fuel problem to me. Hopefully, somebody with more knowledge than me will chime in soon.

 

[Duane(Pa)]

M Tronic? Sounds like might knead a solenoid…

 

[Stump Shot]

An advanced timing can cause this.

 

[MtnHaul]

Can I share my experience and see if anybody else has found the same?
I've got a lot of Stihl chainsaws and some start a lot easier than others.
I often have trouble getting my ported MS261 to start but it runs fine after that.
Recently I spent ages in the woods and gave up, using another saw.

I'd always assumed that if one of my saws was running fine on a particular fuel then I could put the same fuel in the 261 and it should run. NO!!

I've realised that if it has had fresh fuel sitting in it for even a couple of days, then it won't start. Today it did that. I put fresh fuel in it and it started straight away.
The "stale" 2 day old (left in the chainsaw tank) fuel however started instantly in my 500i.

Can anybody explain, or comment on their experience, why some chainsaws seem much more picky about what fuel they'll run with. My 500i and 044 seems to run on anything however ancient.

I thought that you folks on the other side of the pond used the alkylate fuel like Aspen which ought to stay fresh a long while. If the "problem fuel" will work in another saw then I really doubt the fuel has anything to do with it. There has to be another issue. Have you checked or replaced all the easy stuff like spark plug, vent, filter?
I've never noticed one saw performing differently with a given fuel as opposed to another saw. I have been surprised a few times by how long fuel has sat in my old 028 Super and the thing fires right up.



Side note: Last night I watched the first half of the 1984 BBC production of "Threads" and it holds up very well considering it's 42 years old. Still a relevant story line unfortunately.

 

[guym3]

It's not m-tronic. With fresh fuel it runs like a scalded cat. Yes the timings advanced which may contribute.
I picked on the 261 as an issue but that's probably because it's such a good saw that I frequently reach for it to use.
There is a definite ease/difficulty hierarchy in starting many of the Stihls and I've only just recently cottoned on to it being a lot to do with not leaving fuel sitting in the tank for more than a day.
My 044 has advanced timing but will start with any old rubbish in it. Strange.

 

[MtnHaul]

It's not m-tronic. With fresh fuel it runs like a scalded cat. Yes the timings advanced which may contribute.
I picked on the 261 as an issue but that's probably because it's such a good saw that I frequently reach for it to use.
There is a definite ease/difficulty hierarchy in starting many of the Stihls and I've only just recently cottoned on to it being a lot to do with not leaving fuel sitting in the tank for more than a day.
My 044 has advanced timing but will start with any old rubbish in it. Strange.

I use a 261 all the time--what did you gain with the advanced timing?

 

[Ketchup]

We have consistent issues with 261 (non-mtronic) when using winterized fuel in warmer weather. Winterized fuel has additives that cause the fuel to vaporize at a lower temperature. The fuel in the lines and carb turns to gas and inhibits flow of liquid (vapor lock).
I’m not saying this is your issue, but it’s definitely possible if you’re operating above 50F, at higher elevations, or you’re storing the saw in a different pressure zone (like in a black truck toolbox). Typically can gas like Aspen, or Stihl -pre-mix won’t have winterizing additives, but gas does vaporize and 261 is susceptible to vapor lock.

If this is the problem. You can usually break the lock by choke starting, then high idle with the brake off for multiple cycles. It may take 10-15 choke-pop-high idle-pop and die-repeat before the saw will run at high idle. Once it’s running, let it run the chain at high idle for 20-30 seconds. It should be obvious the saw is clearing out vapor and don’t throttle up until the saw runs smooth at high idle. Even then, throttle up carefully and then rev it full bore for few seconds before trying to cut.

In general, always set your saw in the shade when you’re not using it. If you’re running winterized fuel in warmer weather, the vaporlock will start to build as soon as you turn the saw off. If you have the time, put the saw on it’s side and open the gas tank. Winterized gas can often be seen boiling in the gas tank. Just let the saw sit with the cap off and it will boil off most of the winterization in 15-30 minutes. You can do it in the sun to speed it up, but the saw will be very hard to start the first time after.

 

[Poleman]

Like said previously, two day old fuel is not stale …. You've got a saw/carb/ fuel system issue. If the other saw run fine on it and it’s only one saw it’s the saw. Time to look into the saw. Has it always been hard to start since ported??? Probably in the build or failing parts…

 

[guym3]

Thanks for thoughts and it is winterized gas I guess.
I came to start it with fuel that had been in the tank for 2 days in my workshop.
Choke or no choke, I pulled it over 20 times without starting.
Poured that fuel directly into a funnel into my 500i. 500i started second pull.
Put fresh fuel into the 261 and started third pull. Hard not to conclude it's caused by the fuel.
Binary though. Either doesn't fire at all, or runs well, nothing between.

 

[guym3]

I was trying to make the point using the 261 as a more extreme example.
I could pick out the 16 or so Stihl models I've got and rank them in order of how sensitive they are to sub-optimal fuel. 500i 044 least 211 261 most.
Wondered why that was??
The 261 spent this morning bucking logs with fresh fuel and never put a foot wrong.

 

[dangerousatom]

Have you ever pulled and replaced the vent on the gas tank?

It sounds like what others have alluded to. Either the tank is getting slightly pressurized via heat from running or sun and pushing air or fuel vapor into the carb. Id assume when you swap out the fuel your introducing cold fuel to the system and that is where the majority of the fix is created...? Have you taken account of how much fuel is in the saw when the no start happens? Maybe the filter is not falling below the fuel level when stored, it could be hanging up in some particular place. You can try one of two trick's for that. Shorten the hose by 1/2" - 1cm or wrap the filter with a bit of non-flux solder.

IMO try pumping fuel like 20x before choke starting, that will often clear any vapor/air in the system. If not start it on the ground with your knee on the top cover ( holding it down ) finger on the trigger. This is how I have to start my first gen 562xp that has hot fuel issues all the time.

 

[lehman live edge slab]

I was trying to make the point using the 261 as a more extreme example.
I could pick out the 16 or so Stihl models I've got and rank them in order of how sensitive they are to sub-optimal fuel. 500i 044 least 211 261 most.
Wondered why that was??
The 261 spent this morning bucking logs with fresh fuel and never put a foot wrong.

As said many times it’s not the fuel it doesn’t go bad in two days, if it’s because of being vapor locked from in the shop just as an experiment leave it out in the cold overnight with fuel in it to see how it starts. Then if not that see how much timing is added and maybe back it off a bit if needed.

 

[FederalQ]

What octane value gasoline are you using? I know that can be different numbers in some countries but a higher octane would be more resistant to pre ignition. It seems the smaller cc engines have issue and not the larger in your situation.

 

[Ketchup]

261 is more lock prone than many other saws. I’m not sure where in the fuel system the problem lies, but my suspicion is the metering side or the main jet of the carb. It’s interesting you are getting zero start. Usually a vapor locked saw will struggle a bit.

If you feel like experimenting, I’m curious if pouring the “old” mix back in will cause a failed start. Also curious if priming through the carb would solve the hard start and if it would come back after.

Obviously 500i is a totally different fuel system. 440 runs a Walbro HD which is notably larger and older than the little Zama Strato carb in a 261. The V1 261 carb has notably different behavior than the later carbs for that model, though (from memory) I think they share a model number.

Definitely ditch the winterized fuel. It sucks in all saws. 500i will vapor lock and is nearly impossible to restart.

 

[guym3]

Thanks for your thoughts. A few things to try there. Running 99 RON fuel so that shouldn't be a problem

 

[dangerousatom]

What octane value gasoline are you using? I know that can be different numbers in some countries but a higher octane would be more resistant to pre ignition. It seems the smaller cc engines have issue and not the larger in your situation.

USA is known world wide for its lower then most octane. He's in the EU/ Englang so I wouldn't be surprised if he cant even get lower then 92
.
.

edit^^^ ah there ya go

 

[drumbum]

Mmmmmm......solenoid biscuits