Hot Starting/Vapor Lock Issues (E10?)

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I figured I'd revive this thread as the topic has come up several times recently. Just taking a quick break from working outside - my Ryobi 10532/GZ400 just vapor locked on me. It's barely 70F, but this is E10 and surely still winter blend too. I had shut it down long enough to use the loader to push down several large briers and move some rocks from the path I was clearing, so maybe 15min? Anyway, that saw does not have an automatic choke release when you hit the throttle, so I topped off the tank with fresh fuel from the can and was able to get it going on full choke, then keep it running on about 90% choke until it cooled off.

Then of course I immediately tapped a rock.
 
I figured I'd revive this thread as the topic has come up several times recently. Just taking a quick break from working outside - my Ryobi 10532/GZ400 just vapor locked on me. It's barely 70F, but this is E10 and surely still winter blend too. I had shut it down long enough to use the loader to push down several large briers and move some rocks from the path I was clearing, so maybe 15min? Anyway, that saw does not have an automatic choke release when you hit the throttle, so I topped off the tank with fresh fuel from the can and was able to get it going on full choke, then keep it running on about 90% choke until it cooled off.

Then of course I immediately tapped a rock.
chris-

where i live, high in the rockies, some days it's 100f some days it's 10f. i use ethanol free 89 octane from a local station and i don't have any problems (at least not with the saws.) i don't use small saws lke you do, except for climbing. i work on saws for the guys in my village and i tell them that $5/quart fuel is a lot cheaper than paying me to replace their carbs every spring but they don't listen. i've been trying to convince my neighbor to stop burning ethanol contaminated fuel in his tractor (i burn ethanol free 50:1 mix in mine) but he is "problem focused" and misses the solution. so, i sometimes have to fix his ford 600 too. ethanol is making a lot of money for a few (1%) people who don't need it. the rest of us are taking it in the rear. my advise, find a source for good fuel. 'nuff said.
 
find a source for good fuel. 'nuff said.
Like I said, I think ethanol in fuel is stupid for a variety of reasons, mainly that it takes more energy to make the ethanol than you get back in the fuel. It's never been anything other than a way to divert public funds into the hands of a wealthy and connected few through the vehicle of big ag. That said, I don't have much trouble with it other than occasionally having to drain water out of tractors and such that sit outside, and the constant vapor lock issue. I don't have to do carb kits and I don't do much special in the way of precautions - I dump fuel more than a few months old into the lawn equipment. I'll keep getting my fuel from the station 3/4mi away.
 
I'm not sure if it is an ethanol problem. My other thread about my PP5020 could be doing the same thing. I did not try it after it cooled off, I just used a different saw. And I am using 89 non ethanol. I will try and run it this evening to check it out.
 
...having to drain water out of tractors ...

glad to hear you're dodging bullets. i see tractor fuel tanks that are rusted out, even though i live in a semi-arid climate at 6000 ft. i see fuel lines and other plastics that deteriorate when exposed to ethanol and have to be replaced. if it's a typical poulan like i see around here, it often a better risk to buy a new saw than to replace a carb and fuel lines.

i drive my 30mi round trip to get real gasoline about once a month. i usually buy 15 gallons. in early spring, like now, i need more. i run it in my saws, my ford 8n, my f250 farm truck, my rototillers, irrigation pump etc. want to know what ethanol does to a ford truck's fuel pump and fuel gauge sensor? to replace them you have to drop the tanks (there are two.) they weigh 80 - 100 lbs depending on residual fuel. i burn ethanol contaminated gas in my car. a tank only lasts about two weeks so it doesn't go bad.

too bad i can't afford to bribe.... er, contribute to... a senator. end of rant.
 
I'm not sure if it is an ethanol problem.
Vapor lock was an issue with carbs long before ethanol - especially with winter blend fuel that adds butane to make it vaporize more easily in low temperatures. Winter blend fuel is probably still coming through the system, especially if you use higher octane than 87. E10 just makes it worse.
 
want to know what ethanol does to a ford truck's fuel pump and fuel gauge sensor? to replace them you have to drop the tanks (there are two.) they weigh 80 - 100 lbs depending on residual fuel.
LOL, I've dropped both on my '94 F250, one for the fuel pump and one for the rusted rear tank.
 
LOL, I've dropped both on my '94 F250, one for the fuel pump and one for the rusted rear tank.

This is the first year in quite a while that i haven't had a lot of saws come in with screwed-up fuel systems. maybe it's because last year i told all the hombres that next year i wasn't going to cut them a good deal on the repair. here most guys just leave their saw in the shed over the winter without emptying the fuel. so it sits there for six months until its time to get permits and start cutting. if they take them to the local stihl shop, they'll need vasoline, not gasoline.
 
LOL, I've dropped both on my '94 F250, one for the fuel pump and one for the rusted rear tank.

the rear one rusts out because most guys rarely switch from the front to rear. i try to switch every time a fuel up. i've seen the gasket for the fuel pump "plate," on the top, dry up and blow away too. then you can get 25 gallons in the 19 gallon tank...
 
Vapor lock was an issue with carbs long before ethanol - especially with winter blend fuel that adds butane to make it vaporize more easily in low temperatures. Winter blend fuel is probably still coming through the system, especially if you use higher octane than 87. E10 just makes it worse.

chris-

something i experienced several years ago (anything past ten minutes is ancient history for me.) makita 6400 with 84cc retrofit. on a hot day especially in big wood, it would just die and refuse to restart until it cooled, usually at least an hour. problem solved when i removed the ignition module and cleaned out all the schmutz that had built up around it. guy before me had run mostly with a dull chain and the module was totally buried in oily cornmeal. got me thinking about semi-conductors and how most only work in a fairly narrow thermal range. my theory is that the rev limiter was operating full time when hot. i've only confirmed vapor lock on cars and trucks where the fuel pump and/or carb were bolted to some hot part of the block or manifold. seems unlikely that it could happen when fuel components are attached only to rubber and plastic, which are poor conductors. i suggest you try to get your saw to fail on the next hot day and then check for a strong spark.
 
chris-

something i experienced several years ago (anything past ten minutes is ancient history for me.) makita 6400 with 84cc retrofit. on a hot day especially in big wood, it would just die and refuse to restart until it cooled, usually at least an hour. problem solved when i removed the ignition module and cleaned out all the schmutz that had built up around it. guy before me had run mostly with a dull chain and the module was totally buried in oily cornmeal. got me thinking about semi-conductors and how most only work in a fairly narrow thermal range. my theory is that the rev limiter was operating full time when hot. i've only confirmed vapor lock on cars and trucks where the fuel pump and/or carb were bolted to some hot part of the block or manifold. seems unlikely that it could happen when fuel components are attached only to rubber and plastic, which are poor conductors. i suggest you try to get your saw to fail on the next hot day and then check for a strong spark.
But that is a (subtly) different symptom, as my vapor locked saws never cut out while running. Vapor lock occurs only after the saw is shut off for a long enough time for heat built up in the engine to cook out and heat the carb. Then, if you take that hot saw on a hot day and give it full choke, you can get it to start again and nurse it back to running again. And once it's running again, it will cut fine with no issues until it's shut off again.

These are pretty compact units, and once the air flow stops the engine and carb are mostly enclosed - so you've got that hot cylinder with fins to heat the air in there, and it has much more mass than the cool carb.
 
But that is a (subtly) different symptom, as my vapor locked saws never cut out while running. Vapor lock occurs only after the saw is shut off for a long enough time for heat built up in the engine to cook out and heat the carb. Then, if you take that hot saw on a hot day and give it full choke, you can get it to start again and nurse it back to running again. And once it's running again, it will cut fine with no issues until it's shut off again.

These are pretty compact units, and once the air flow stops the engine and carb are mostly enclosed - so you've got that hot cylinder with fins to heat the air in there, and it has much more mass than the cool carb.

interesting observations. it would help if you had the thermometer probe and i.r. probe for your fluke meter and one of those mini battery powered oscilloscopes to check the electronics.

i worked on an 036 today, lots of problems, but after i replaced the fuel tank (a gorilla had broken the choke linkage), the carb, and several other things, i found the fuel line in the new tank had turned to gunk after being stored all winter with ethanol in the tank. had to drive to town for a new fuel line and filter. wanted some old spice to splash into the smelly fuel tank. it's running like a scalded cat now. the 036 and 046 are the top of the stihl line. it's been downhill since then.
 
Sometimes I've had 372 that when ran hot and hard they would tend to rev higher than idle want to race. I would say they may have had a very small leak when they got very hot.
It was never vent related as it didn't settle down when I opened the gas cap. Much like a frozen vent would act.

When I used to cut Seismic lines with my Walkerized 357 that would happen when hot. It wouldn't prime hot after I would it shut down. That's just where I had the low tuned. That's where the saw ran the smoothest and fastest and still had jump. If I backed the low off a little bit it would prime no problem but had a rattle that my hands didn't like. I just tried to fuel with it running. Did you try fattening up the low on the hot days?
Nothing to speak of that I couldn't tune out or melt out in the winter.

*Different 'fuel issue':
When I got this 346 it was really hot weather at the time. It ran great but once I shut it down I couldn't get it going for 15 min....do you know what caused it?
 
Sometimes I've had 372 that when ran hot and hard they would tend to rev higher than idle want to race. I would say they may have had a very small leak when they got very hot.
It was never vent related as it didn't settle down when I opened the gas cap. Much like a frozen vent would act.

When I used to cut Seismic lines with my Walkerized 357 that would happen when hot. It wouldn't prime hot after I would it shut down. That's just where I had the low tuned. That's where the saw ran the smoothest and fastest and still had jump. If I backed the low off a little bit it would prime no problem but had a rattle that my hands didn't like. I just tried to fuel with it running. Did you try fattening up the low on the hot days?
Nothing to speak of that I couldn't tune out or melt out in the winter.

*Different 'fuel issue':
When I got this 346 it was really hot weather at the time. It ran great but once I shut it down I couldn't get it going for 15 min....do you know what caused it?

west-

i didn't know it gets hot in b.c.

i like your ideas about the low speed adjustment.. i think it's more important now. newer epa carbs seem to run the H really lean and need the L richer to keep the saw working right at high rpm's. i just fixed an echo 670 that wouldn't start at all until you opened the L 2.5 to 3 turns. and to get it running right at speed required close attention to the L setting.

your experiences with the 346 sound similar to chris-pa's. thats a hot little saw, a screamer. maybe it gets too hot. if it will restart in 15 minutes, that sounds like a fuel issue to me. if it takes longer, electronics. the iron and plastic ignition module, bolted to the case, should take longer to cool than the carb and fuel lines. i also wonder if this sort of problem is more common on saws with purge bulbs. i've always thought they are a solution for a non-existent problem.
 
Sometimes I've had 372 that when ran hot and hard they would tend to rev higher than idle want to race. I would say they may have had a very small leak when they got very hot.
It was never vent related as it didn't settle down when I opened the gas cap. Much like a frozen vent would act.

When I used to cut Seismic lines with my Walkerized 357 that would happen when hot. It wouldn't prime hot after I would it shut down. That's just where I had the low tuned. That's where the saw ran the smoothest and fastest and still had jump. If I backed the low off a little bit it would prime no problem but had a rattle that my hands didn't like. I just tried to fuel with it running. Did you try fattening up the low on the hot days?
Nothing to speak of that I couldn't tune out or melt out in the winter.

*Different 'fuel issue':
When I got this 346 it was really hot weather at the time. It ran great but once I shut it down I couldn't get it going for 15 min....do you know what caused it?
In general, hotter air needs a leaner mixture since it has fewer oxygen molecules per unit volume.

Here though, I've played with needle setting and all manner of stuff on the way to diagnosing this problem, and none of it made any difference because the carb has no fuel. Recall that get these started and running for often quite a long time on 80-100% choke. Compared to that a tweak of the L needles isn't going to matter. Only full choke could pull enough vapor through the lines to get it to fire. Eventually it pulls enough air through the carb (plus the fan) to cool it off and work normally again, with no tuning changes at all.

It's possible a richer L might be helpful if you let it idle that way before shutting down, due to increased evaporative cooling from the extra fuel.

As to the 346 - it sounds like vapor lock. If you can get it to fire and chug a bit on full choke when it does it that will prove it. Of course, if it's not vapor lock you'll flood the heck out of it.....
 
In general, hotter air needs a leaner mixture since it has fewer oxygen molecules per unit volume.

Here though, I've played with needle setting and all manner of stuff on the way to diagnosing this problem, and none of it made any difference because the carb has no fuel. Recall that get these started and running for often quite a long time on 80-100% choke. Compared to that a tweak of the L needles isn't going to matter. Only full choke could pull enough vapor through the lines to get it to fire. Eventually it pulls enough air through the carb (plus the fan) to cool it off and work normally again, with no tuning changes at all.

It's possible a richer L might be helpful if you let it idle that way before shutting down, due to increased evaporative cooling from the extra fuel.

As to the 346 - it sounds like vapor lock. If you can get it to fire and chug a bit on full choke when it does it that will prove it. Of course, if it's not vapor lock you'll flood the heck out of it.....
good thoughts chris, but.. could you explain (defend) your hypothesis that hot air has fewer oxygen molecules and if so quantify the difference so i know how much to tweek the little screw. where did the missing ones go?
 
west-

i didn't know it gets hot in b.c.

i like your ideas about the low speed adjustment.. i think it's more important now. newer epa carbs seem to run the H really lean and need the L richer to keep the saw working right at high rpm's. i just fixed an echo 670 that wouldn't start at all until you opened the L 2.5 to 3 turns. and to get it running right at speed required close attention to the L setting.

your experiences with the 346 sound similar to chris-pa's. thats a hot little saw, a screamer. maybe it gets too hot. if it will restart in 15 minutes, that sounds like a fuel issue to me. if it takes longer, electronics. the iron and plastic ignition module, bolted to the case, should take longer to cool than the carb and fuel lines. i also wonder if this sort of problem is more common on saws with purge bulbs. i've always thought they are a solution for a non-existent problem.
Ha-ha, yes sounds like It could be? I'm not a fan of the purge bulb. I eliminated it on that 346 as it wasn't the prime problem (bad pun srry lol) but certainly made the problem hard to diagnose. You are right, when I started reading Chris's OP, I figured it was the same thing until I read on. It was actually the opposite.
(Explanation below)
I personally have had terrible luck was carbs these past 5-6 years. (All Walbro)I have had as little as 4 months on a new carb. Quallity has droped somewhere? Its like night & day. After reading your posts I am strongly weighing towards the ethanol been the problem perhaps A higher content than they say at the pumps ("up to 10%"). Maybe because of the winter grades in Northan BC & AB chasing Gas & Oil and Mountain Pine Beetle work up there. I have never been In a position I could supply my own fuel but for now I'm just out of greater Vancouver Falling for property development and having read you post I realize I do have an Ethanol free source through Shell Canada (V Power) I will be shopping there from now in.
Great history you have come forth with, thanks.

It can get very hot up here. On the coast you may see a few days through the summer in the lower 90's but hot days would typically be between 80 to 87.
BC shares the Okanogan region with North Eastern WA and it's smokin' hot there. It's all orchards, BC puts out a lot of wine from there. Canada's only desert (Okanagan desert) in Osoyoos is the top of the Sonoran. Most of the BC interior is too hot for me.



It's possible a richer L might be helpful if you let it idle that way before shutting down, due to increased evaporative cooling from the extra fuel.

As to the 346 - it sounds like vapor lock. If you can get it to fire and chug a bit on full choke when it does it that will prove it. Of course, if it's not vapor lock you'll flood the heck out of it.....

Yes I do recall you saying you needed to choke it.

I Was and am referring to a richer low for these conditions.

A hard starting saw is an indication of a lean low. May not slow the response as it didn't in the case of the ported 357 in hot weather. It creates heat and seems to interfere with priming of sort?..I have no technical response for it. Although that's where I preferred to run the saw but it was set wrong for that temperature. Providing there is no other issues with a saw then a properly set low of a hot saw should fire up with a half a pull. If it needs a little more low in hot weather then that's what we do.
Seasons, Elevations & Activities.

I remember my builder sending different saws to me from sea level
to the same places in the North at opposite seasons. I'm not comparing his tune at sea level to elevation in one season but in many seasons. I possibly tuned 30 saws for myself and others that purchased them. Sometimes the low was the same as his and other times it could be more than half a turn different. Maybe my example dosen't hold much weigh as the weather changes on his end too. Interesting for me anyway. I guess the point is we need to pay attention to obvious and not so obvious changes. Tunning is an ever changing thing.

The 346 had a bad vent but didn't show signs like it was leaning coming of the trigger. It must have been pressuring up and pushing fuel through the primer I assume, giving it the right amount. I figured it was needing more low but eventually figured it on removal of the cap and filter, it was self priming and flooding but hard to detect. I put a vent in and eliminated the bulb.
Good little saw. That was a tough little trouble shoot. Yes more pieces more proplems.

Interesting thread Chris. I enjoy your technical knowledge
Thnx
 
Ha-ha, yes sounds like It could be? I'm not a fan of the purge bulb. I eliminated it on that 346 as it wasn't the prime problem (bad pun srry lol) but certainly made the problem hard to diagnose. You are right, when I started reading Chris's OP, I figured it was the same thing until I read on. It was actually the opposite.
(Explanation below)
I personally have had terrible luck was carbs these past 5-6 years. (All Walbro)I have had as little as 4 months on a new carb. Quallity has droped somewhere? Its like night & day. After reading your posts I am strongly weighing towards the ethanol been the problem perhaps A higher content than they say at the pumps ("up to 10%"). Maybe because of the winter grades in Northan BC & AB chasing Gas & Oil and Mountain Pine Beetle work up there. I have never been In a position I could supply my own fuel but for now I'm just out of greater Vancouver Falling for property development and having read you post I realize I do have an Ethanol free source through Shell Canada (V Power) I will be shopping there from now in.
Great history you have come forth with, thanks.

It can get very hot up here. On the coast you may see a few days through the summer in the lower 90's but hot days would typically be between 80 to 87.
BC shares the Okanogan region with North Eastern WA and it's smokin' hot there. It's all orchards, BC puts out a lot of wine from there. Canada's only desert (Okanagan desert) in Osoyoos is the top of the Sonoran. Most of the BC interior is too hot for me.
west-

at this point, i seldom even try to rebuild carbs. it's always a crap shoot, $20 in expenses and an hour of time, more if that little spring slips into a parallel universe. and sometimes it works and sometimes it doesn't. most likely it's ethanol damaging plastic valve seats, but i can't prove it. it's easier and often cheaper to just buy a new carb and use real gasoline. also, carbs with purge bulbs have an extra valve which adds another layer of complication. i don't have problems with my own carbs but i don't use ethanol.

thanks for the geography lesson. i didn't know that eastern b.c. is hot and dry. it sounds a lot like where i live, 6000 ft. in the southernmost rocky mountains. in the spring and summer it can be 45f when you start and 100f by mid-afternoon. and it can be 5000ft in big cottonwoods down by the rio grande or 8000ft in ponderosa, spruce and aspen up on the mountain.
 
good thoughts chris, but.. could you explain (defend) your hypothesis that hot air has fewer oxygen molecules and if so quantify the difference so i know how much to tweek the little screw. where did the missing ones go?
Pretty straightforward: Air expands as it gets hotter, which means more distance between molecules, so a given volume of air holds fewer molecules. A carb responds primarily to the velocity of the air moving through it, which is volume per second, rather than density.

As the air warms the carb adds the same amount of fuel based on velocity (volume), but there are fewer oxygen molecules in the hotter air, so it' snow too much fuel.

I don't know how to get from the percentage of expansion of air to how many turns on the screw!
 
I don't know how to get from the percentage of expansion of air to how many turns on the screw!
There is only one way to know these things.
You could do all kinds of testing throughout the year in one specific area and I'm sure the changes would be very slight on the dial just as I found with the low jet in extreme heat, I may have moved it between an 1/8 - 1/16.

Saws are set at sea level from factories as I know Husqvarna's are.
I take the limiters off mine but I have set other guys saws up working in elevation and often find there wasn't enough throw allowance to richen the low at factory limits.

Just after I Posting last night something jogged my memory and I remember being on a big heli portable Seismic job up in Tumbler ridge BC probably 2008. We cut up there about 3 summers in a row. It usually went to an early shift and that ment a 1:00PM shut down. 2007 we completely got shut down for 2 weeks for heat. Anyway, there would be 80 -100 cutters on each job. One hot day a hand full of guys had what sounds like what you are describing, happen. I remember it was talked about at the saftey meeting. It seemed to go on for a few days in a row. It happend to a Faller friend of mine in that time. He is a really straight up guy and he said his gas for literally boiling? or what appeared to him that was happening. other symptoms IDK?
I can't remember but I can definitely attest to this phenomena happening to a small group on a big 3D job in "Tumbler".
I will try get hold of James and ask him about that.
James was running a 460, I'm not sure if the other guys were running Stihl also?
 
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