Hot Starting/Vapor Lock Issues (E10?)

[heyduke]

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?

west-

yes, i've experienced what seemed to be gas boiling in the tank during really hot weather. i don't remember it causing my saw not to run though. regarding carb adjustments for heat, i'm not buying it. i set my carbs for 6000 feet and they're good for 5000 to 8000, summer or winter. however... newer carbs, all bets are off. i suspect the H jets are smaller diameter and backing the needles out doesn't have any effect after a couple of turns. i think there are some carbs that don't even have adjustable H jets. i just finished putting together an old stihl 036 and it reminded me how much easier it used to be to tune a saw. took maybe 30 seconds to tweek H and L. took it out to the wood pile and buried the bar in a piece of hardwood. it threw fat chips ten feet.

 

[heyduke]

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!

Interesting thoughts but... i suspect atmospheric pressure is much more significant and the tuning on my saws seems to be stable rain or shine. also, during really hot days the atmospheric pressure is usually abnormally high.

 

[Chris-PA]

It's in the high 80's today and the 42cc Poulan I was using was vapor locking as usual. Had to start it hot on full choke the one time I had it off for a little too long, but got it going again. I let it idle more than I usually would rather than shut it down, and I'm pretty fast at re-fueling. The larger fuel cap on those is a help!

 

[heyduke]

It's in the high 80's today and the 42cc Poulan I was using was vapor locking as usual. Had to start it hot on full choke the one time I had it off for a little too long, but got it going again. I let it idle more than I usually would rather than shut it down, and I'm pretty fast at re-fueling. The larger fuel cap on those is a help!

get outa the kitchen if... aw heck. you've got to be able to find the root cause for this. my only advice now is, don't think you know the answer. be open minded test things that you think are ok. i always say, when you know the answer, that's when you're in trouble. we used to be able to get aerosol cans of coolant that you could spray on electronics components to find thermal problems, just brainstorming...

 

[Chris-PA]

get outa the kitchen if... aw heck. you've got to be able to find the root cause for this. my only advice now is, don't think you know the answer. be open minded test things that you think are ok. i always say, when you know the answer, that's when you're in trouble. we used to be able to get aerosol cans of coolant that you could spray on electronics components to find thermal problems, just brainstorming...

Well, I only think I know the root cause because I've spent years trying to figure it out. All of the stuff outlined above - E10 fuel + winter blend fuel with extra butane, starting on full choke when hot, etc. It all adds up.

I don't doubt at all that having my saws modified adds to heat load. Still, the E10 fuel is a big contributer.

 

[GrassGuerilla]

Only trouble I have with your hypothesis Chris is why isn't this a plague in hotter areas? You ain't exactly in the hot zone. Seems like the guys down south would be having fits? No?

 

[Chris-PA]

Only trouble I have with your hypothesis Chris is why isn't this a plague in hotter areas? You ain't exactly in the hot zone. Seems like the guys down south would be having fits? No?

It's certainly a valid point. Still, I have it happen regularly on several types of saw, so I don't think it's the saw. Also there is a steady stream of posts describing the same symptoms from various locations, especially when the weather starts to warm up.

The fuel distribution systems are not all interconnected, and the ethanol is added at the end of the line, so fuel blend can vary from place to place.

 

[heyduke]

Well, I only think I know the root cause because I've spent years trying to figure it out. All of the stuff outlined above - E10 fuel + winter blend fuel with extra butane, starting on full choke when hot, etc. It all adds up.

I don't doubt at all that having my saws modified adds to heat load. Still, the E10 fuel is a big contributer.

if you know the root cause fix it. if you can't fix it you don't know the root cause.

maybe get some real gasoline and see if that helps. it's $6 for a quart. ain't going to contribute to your bankruptcy. at this point you've got hypotheses without much experimental data. any crackpot can come up with hypotheses. a scientist can devise and run experiments.

 

[GrassGuerilla]

You can make your own ethanol free gas with little more than a pint or so of tap water, a gallon of 91+ octane ethanol laden pump gas, a glass carboy and a siphon hose. It doesn't have to be expensive...

Add the water to the pump gas, shake poor it into the carboy and let it separate (I wait overnight) siphon the now pure gas off the top. This simply uses the same process of phase separation we usually fear in our favor. Why fight it? It wants to separate, just let it. It loses approx 2-3 points of octane, so start with 91-93 and it'll be fine. Yeah, it's a PITA for daily use, but worth the trouble for occasional use tools or to purge all ethanol before storage.

 

[lone wolf]

It's certainly a valid point. Still, I have it happen regularly on several types of saw, so I don't think it's the saw. Also there is a steady stream of posts describing the same symptoms from various locations, especially when the weather starts to warm up.

The fuel distribution systems are not all interconnected, and the ethanol is added at the end of the line, so fuel blend can vary from place to place.

Did you test the percentage of ethanol?

 

[heyduke]

You can make your own ethanol free gas with little more than a pint or so of tap water, a gallon of 91+ octane ethanol laden pump gas, a glass carboy and a siphon hose. It doesn't have to be expensive...

Add the water to the pump gas, shake poor it into the carboy and let it separate (I wait overnight) siphon the now pure gas off the top. This simply uses the same process of phase separation we usually fear in our favor. Why fight it? It wants to separate, just let it. It loses approx 2-3 points of octane, so start with 91-93 and it'll be fine. Yeah, it's a PITA for daily use, but worth the trouble for occasional use tools or to purge all ethanol before storage.

that will work. the hardest part is finding good apparatus to siphon off the petroleum without getting any water. one solution that might work is stopper and glass tube in the carboy, the glass tube far enough into carboy to be above the water level when inverted. a bonus benefit is you get to see how dirty and funky the ethanol is, not pretty but instructive. you won't be tempted to drink it. octane is an unknown, may be higher or lower. i don't know how to measure it but having high octane won't damage your saw or degrade performance. low octane can cause detonation at worst and make your ignition timing a little too retarded at best. on the other hand, almost everyone lives fairly close to a small airport. be nice and they will sell you low-lead fuel. it costs a little more than your local station's, but solves the problem. guys will tell you that flame propagation rate is a problem but i sure haven't seen any data to support that.

 

[GrassGuerilla]

I just use a length of fuel line. I'm not worried about getting every last drop, I leave a bit behind rather than suck up any ethanol laden water. And yes, the results will surprise you. Sometimes the leftover emulsion is clear, sometimes it looks like a mud puddle. The swill that passes for pump gas is scary.

What starts as 93 octane end up around 90-91. If you start with 91, you can expect 88-89 as a final product. Good news it's now it's stable for up to two years.

 

[heyduke]

I just use a length of fuel line. I'm not worried about getting every last drop, I leave a bit behind rather than suck up any ethanol laden water. And yes, the results will surprise you. Sometimes the leftover emulsion is clear, sometimes it looks like a mud puddle. The swill that passes for pump gas is scary.

What starts as 93 octane end up around 90-91. If you start with 91, you can expect 88-89 as a final product. Good news it's now it's stable for up to two years.

yeah, a fuel line, copper tube or glass should work. you can get rubber corks with holes for one or two tubes (don't forget one for air) at any beer brewing supply, carboys too. i've thought about making an apparatus with a length of 4" drainage pipe, maybe five feet long but i haven't done it yet. one problem is that the water/alcohol will cling to the sides of your container and mix with your petroelum as you drain it. an inverted container solves that problem.

i usually use a water/pump gas ratio of 1:10. as you said, let it sit overnight. same thing i use for testing only bigger. my test container is 12oz.

 

[heyduke]

I just use a length of fuel line. I'm not worried about getting every last drop, I leave a bit behind rather than suck up any ethanol laden water. And yes, the results will surprise you. Sometimes the leftover emulsion is clear, sometimes it looks like a mud puddle. The swill that passes for pump gas is scary.

What starts as 93 octane end up around 90-91. If you start with 91, you can expect 88-89 as a final product. Good news it's now it's stable for up to two years.

regarding octane, i don't know how your measuring it. let us know. but i suspect that regardless of octane you will have superior fuel. the best alcohol only has about 75% of the btu's per volume of gasoline. i don't know if you've noticed but the mileage on your truck varies wildly now depending on the ratio and quality of the alcohol that is blended in.

 

[Chris-PA]

Well, it is already proven to my satisfaction. This thread is quite old now and it had been going on for quite some time before I started it, and it has been a consistent problem all along since. It happens on multiple saws of multiple different designs.

There really isn't any other way you can get a very hot saw to start - and continue to run - on full choke! And then run perfectly fine once it gets a little air flow and cools off.

I'm sure I could try other fuels, but I'm not going to. These are just chainsaws and they'll have to run on whatever I get from the corner station. At the moment that's spiked with ethanol, and I posted a reference upthread showing that makes it worse, which is again consistent. The volume of ethanol may be varying, but I have not noticed that the symptoms change much - in the spring it happens even at lower temperatures, but once it's warmer out they will all do it once the saws get hot and then heal soak for a few minutes.

The purpose of this thread was mostly to let others know about the issue. I'd already done my time hauling saws back down to the barn, tearing apart fuel systems and engines, only to find there was never anything wrong with them to begin with. Now we have threads about new pro saws that don't work, and it's clear to me they're dealing with the same problem.

I have no doubt the engineers are scratching their heads on this too, as it's not a trivial problem to solve. The restart issue comes in when the saw is off - there is no air flow and not much you can do. You can try to reduce temperatures while the saw is still running (like the new 562 top cover), but you still have to deal with very hot parts in the engine at shut off which will heat up the fuel system parts under the covers once it shuts off.

I'm wondering if any of the saws have vapor lock issues while they're still running? Mine don't seem to*, but it was not uncommon on cars back in the day. If this happens you'll get a lean mixture. If there is a connection to AT/MT, this might be it. Prior to feedback carbs the uncontrolled mixture was providing lots of extra fuel - one consequence of getting the mixture under control is that the evaporative cooling from that extra fuel is also gone. So Husqvarna is adding cooling vents in their top covers, and Stihl is enriching the mixture on their 661's......

*One of my strato GZ4000 clones was behaving very strangely yesterday, and might have been vapor locking while running. It's going to take some more evaluation to figure that out. I could not tune it and it would take off revving and then dog down. I checked the fuel system and pulled the muffler to look for soring (it was fine). I swapped the ignition out and will try it again - but it may be a while until it's hot enough to tell.

 

[heyduke]

Well, it is already proven to my satisfaction. This thread is quite old now and it had been going on for quite some time before I started it, and it has been a consistent problem all along since. It happens on multiple saws of multiple different designs.

There really isn't any other way you can get a very hot saw to start - and continue to run - on full choke! And then run perfectly fine once it gets a little air flow and cools off.

I'm sure I could try other fuels, but I'm not going to. These are just chainsaws and they'll have to run on whatever I get from the corner station. At the moment that's spiked with ethanol, and I posted a reference upthread showing that makes it worse, which is again consistent. The volume of ethanol may be varying, but I have not noticed that the symptoms change much - in the spring it happens even at lower temperatures, but once it's warmer out they will all do it once the saws get hot and then heal soak for a few minutes.

The purpose of this thread was mostly to let others know about the issue. I'd already done my time hauling saws back down to the barn, tearing apart fuel systems and engines, only to find there was never anything wrong with them to begin with. Now we have threads about new pro saws that don't work, and it's clear to me they're dealing with the same problem.

I have no doubt the engineers are scratching their heads on this too, as it's not a trivial problem to solve. The restart issue comes in when the saw is off - there is no air flow and not much you can do. You can try to reduce temperatures while the saw is still running (like the new 562 top cover), but you still have to deal with very hot parts in the engine at shut off which will heat up the fuel system parts under the covers once it shuts off.

I'm wondering if any of the saws have vapor lock issues while they're still running? Mine don't seem to*, but it was not uncommon on cars back in the day. If this happens you'll get a lean mixture. If there is a connection to AT/MT, this might be it. Prior to feedback carbs the uncontrolled mixture was providing lots of extra fuel - one consequence of getting the mixture under control is that the evaporative cooling from that extra fuel is also gone. So Husqvarna is adding cooling vents in their top covers, and Stihl is enriching the mixture on their 661's......

*One of my strato GZ4000 clones was behaving very strangely yesterday, and might have been vapor locking while running. It's going to take some more evaluation to figure that out. I could not tune it and it would take off revving and then dog down. I checked the fuel system and pulled the muffler to look for soring (it was fine). I swapped the ignition out and will try it again - but it may be a while until it's hot enough to tell.

you remind me of the old woman who couldn't get her 49 ford to run right. she hung her purse from the choke rod. guess you may as well make some iced tea and wait for cooler weather.

 

[Chris-PA]

you remind me of the old woman who couldn't get her 49 ford to run right. she hung her purse from the choke rod. guess you may as well make some iced tea and wait for cooler weather.

Nonsense - I deal with the fuel that is available and learn to make it work. I cut wood in all temps, and I get the job done and my saws are not damaged. Understanding the root cause of what I'm dealing with is the key to that. I'm building saws with chokes that don't shut off with the throttle, and find that plastic cased clamshells work better as there is less metal mass to hold heat. My 42cc Poulan clamshells vapor lock routinely, but they are the easiest of my saws to get going again, especially with chokes that stay on. They also have fairly large fans and good cooling - so the heat goes out into the air and has less metal mass to accumulate in. "Master control levers" would be a problem and I won't consider any saw that does not have separate control of the choke.

I have one saw with an alloy case with the fuel tank built into it, and I decided to run that hard the next hot day I'm cutting. I'm curious if that's a problem or if the heated fuel gives more pressure and helps in restarting.

I've also considered designing a heat sink arrangement and/or modified cover to help cool the carb when the saw is off. I still have not decided if cooling the carb or the fuel lines is the better approach. I have not come up with anything I'm happy with yet, but I'll keep pondering it.

 

[heyduke]

Nonsense - I deal with the fuel that is available and learn to make it work. I cut wood in all temps, and I get the job done and my saws are not damaged. Understanding the root cause of what I'm dealing with is the key to that. I'm building saws with chokes that don't shut off with the throttle, and find that plastic cased clamshells work better as there is less metal mass to hold heat. My 42cc Poulan clamshells vapor lock routinely, but they are the easiest of my saws to get going again, especially with chokes that stay on. They also have fairly large fans and good cooling - so the heat goes out into the air and has less metal mass to accumulate in. "Master control levers" would be a problem and I won't consider any saw that does not have separate control of the choke.

I have one saw with an alloy case with the fuel tank built into it, and I decided to run that hard the next hot day I'm cutting. I'm curious if that's a problem or if the heated fuel gives more pressure and helps in restarting.

I've also considered designing a heat sink arrangement and/or modified cover to help cool the carb when the saw is off. I still have not decided if cooling the carb or the fuel lines is the better approach. I have not come up with anything I'm happy with yet, but I'll keep pondering it.

chris- l love ya bro, but you're thinking like an engineer, not a mechanic. a mechanic doesn't know the root cause until he's solved the problem, or to use big, 25 cent words, you don't except a hypothesis until you can support it with repeatable experimental data. believing is an obstacle to finding the truth. i like your idea of using a heatsink. better ventilaton might help too. i don't see why a poulan clamshell should run hotter than a more conventional saw, maybe the lack of an integral oil tank as a heatsinking mass? in my experience an overheated motor always floods when you use the choke. i don't see any hard data supporting vapor lock for that matter, only that you think, no you're sure that is the cause.

 

[GrassGuerilla]

regarding octane, i don't know how your measuring it. let us know. but i suspect that regardless of octane you will have superior fuel. the best alcohol only has about 75% of the btu's per volume of gasoline. i don't know if you've noticed but the mileage on your truck varies wildly now depending on the ratio and quality of the alcohol that is blended in.

I'm actually not measuring octane. Equipment to do so is prohibitively expensive. Having read several times from several sources that the ethanol is expected to boost the octane by 2-4 points, I simply start with premium pump gas and take what's left. Starting with 93 gives me a comfortable buffer.

Here's a good place to start. I figure why not simply use this much dreaded phase separation to our advantage? http://fuelschool.blogspot.com/2009/02/phase-separation-in-ethanol-blended.html?m=1

 

[heyduke]

I'm actually not measuring octane. Equipment to do so is prohibitively expensive. Having read several times from several sources that the ethanol is expected to boost the octane by 2-4 points, I simply start with premium pump gas and take what's left. Starting with 93 gives me a comfortable buffer.

Here's a good place to start. I figure why not simply use this much dreaded phase separation to our advantage? http://fuelschool.blogspot.com/2009/02/phase-separation-in-ethanol-blended.html?m=1

yeah, i've read that too and it must be true 'cuz it's on the internet. i tend to test my fuel and find that the amount of ethanol vairies widely and lower octane fuel doesn't necessarily have less ethanol so i figure that ethanol isn't the main contributer to octane rating. truth is, i don't believe the octane rating on the pump. cars now have a "knock detector" that adjusts timing for the gasoline so you really can't tell. states test the accuracy of pumps and put a sticker on them so the consumer can feel like he's really getting the gallon he's paying for, but i haven't heard about any quality tests. i usually calculate my mileage when i fill up and it varies by 3 to 5 mpg even though my driving doesn't vary much at all. that didn't happen before mandatory ethanol. ethanol has appx. 67% of the btu's of gasoline ( https://en.wikipedia.org/wiki/Gasoline_gallon_equivalent ) so the more ethanol, the worse the mileage.

that being said. this thread is about chris's epic problems. and he needs to eliminate or nail down his fuel as a root cause. i think that if he tested his gasoline like i do, and saw some of the ethanol that falls out of suspension he'd never put another drop of e-10 thru his zamas. that stuff is nasty and full of particulates that were never intended to be used in a chainsaw carb.