Hot Starting/Vapor Lock Issues (E10?)

[Chris-PA]

I was cutting yesterday in the heat (was about 90F), and once again had hot start issues. My saws are clearly vapor locking, as I have to full choke them to get them to fire briefly, then I take off the choke and they'll run for a moment and stall. If I pull them many times on full choke then I can eventually get them running again - they don't flood. I always try to set them down in the shade, and not to let them run out of fuel but rather let them idle a bit before shutting them off, but I still have issues with it.

The saws with purge bulbs will pump vapor when hot - basically the purge becomes useless, but all works fine again when cooled off. Most of my saws have done this in the heat, and they run fine once I get them going and the lines get cleared out again. Given the variety of saws it is not something to do with the saw design, it must be the fuel.

I'm using E10 from the local station with good oil at 40:1. I thought once that this was due to winter fuel blends used in the spring on early hot days, but it's September now so this is unlikely. It may be that they've changed fuel vapor characteristics now that no cars have carburetors, I have no way to know.

Anyway, is anyone else experiencing this? I can't be the only one having hot start issues in the heat. I'd like to understand better why this is happening now.

 

[Termite]

No, I have not experienced this problem but I don't use fuel with ethanol.
Very interesting.

 

[benmyers]

We had a problem like this last summer with a wild thing. Never did figure out what the problem was. Replaced fuel lines and the tank vent I think and haven't had any problems. But it also hasn't been as hit around here this summer.

 

[SS Sniper]

No I don't see this, and I use E10 the majority of the time too.
Interesting to see what the problem is

 

[GrassGuerilla]

What's the spark plug look like in these machines? Any chance they're set a shad lean? Similar effect.

 

[Chris-PA]

What's the spark plug look like in these machines? Any chance they're set a shad lean? Similar effect.

I don't run them puking rich, but they all "4-stroke" when I lift. Plugs look fine. There are no cats to add heat either. It happens if I shut them off and let them sit long enough to heat soak - if I start them back up soon enough there is no problem.

It was darn hot yesterday, but I was cutting in the shade of the woods.

 

[zogger]

Run two saws in a similar manner and time frame, one with your mix, the other canned premix.

 

[Chris-PA]

Run two saws in a similar manner and time frame, one with your mix, the other canned premix.

I suppose that would be an interesting experiment, but I'm pretty convinced already that it is the fuel, and I'm certainly not going to be running canned fuel long term. Also I never know when I'll be cutting in the heat much ahead of time.

Still, if it did it on canned fuel then that would certainly show that it's not the fuel.

I was hoping to find out that others have been experiencing this and to maybe narrow it down from there.

 

[zogger]

I suppose that would be an interesting experiment, but I'm pretty convinced already that it is the fuel, and I'm certainly not going to be running canned fuel long term. Also I never know when I'll be cutting in the heat much ahead of time.

Still, if it did it on canned fuel then that would certainly show that it's not the fuel.

I was hoping to find out that others have been experiencing this and to maybe narrow it down from there.

It's easy enough to do, and I think for five bucks, to be sure it is the fuel or something else, it is worth doing.

 

[TPA]

Pure gas dot org shows lots of gas stations that sell ethanol free in PA. I quit ethanol gas for outdoor equipment about 2 years ago and all my carb problems are gone.

 

[Jeff Lary]

Chris I love you deeply,...... but dude you got saw issues. 90 degrees and your going to run a saw ? I would never make a living in the woods I know but 90 is a little excessive aint it? Holy smoke man have a beer, plan your winter cutting, cook a burger, go swimming..... but run a saw ... I would rather have my scrotum in a vise with a drunken enemy turning the handle . Really I would. Take care you sick individual. Jeff

 

[Chris-PA]

Chris I love you deeply,...... but dude you got saw issues. 90 degrees and your going to run a saw ? I would never make a living in the woods I know but 90 is a little excessive aint it? Holy smoke man have a beer, plan your winter cutting, cook a burger, go swimming..... but run a saw ... I would rather have my scrotum in a vise with a drunken enemy turning the handle . Really I would. Take care you sick individual. Jeff

Ha - thanks Jeff, but there are so few days left to gather wood before cold weather gets here, and I have some standing dead ash I can burn this year if I get it stacked now. Given the way the weather is these days, if it isn't pouring it's a good time to run a saw and swing an axe, regardless of the temperature. It's does take it out of me though.

Pure gas dot org shows lots of gas stations that sell ethanol free in PA. I quit ethanol gas for outdoor equipment about 2 years ago and all my carb problems are gone.

Yes, but I'm not at all sure it is the ethanol. I didn't think it vaporized at a lower temperature, but I could be wrong. I guess I'll have to look it up. I guess I'm trying to avoid experimenting with different fuel mixes.

 

[Chris-PA]

Well, I guess I found it:

"Volatility and distillation
Ethanol forms azeotropes with hydrocarbons of gasoline, which impacts volatility. In particular, the vapor pressure and distillation characteristics of ethanol/gasoline blends are non-linear. Blending vapor pressures for alcohols are significantly higher than their nominal vapor pressures. Vapor pressure of neat ethanol is low at only 16 kPa (Owen and Coley 1995). When ethanol is added into gasoline, vapor pressure increases with blending ratios of 5-10%, but then gradually declines (Figures). With ethanol content of some 30-50%, vapor pressure is at the same level as for gasoline without oxygenates (Environment Australia 2002, Furey 1985).


Vapor pressure of blends can be adjusted by using base fuel with low vapor pressure. If strict fuel specifications are to be met, this rules out the possibility of so-called splash-blending of ethanol. In some regions, higher vapor pressures are allowed for gasoline-ethanol blends, if they contain ethanol (Read more of volatility limits).


One notable point regarding the vapor pressure of ethanol blend is its tendency to increase more quickly than that of gasoline with increasing temperature."

From: http://www.iea-amf.org/content/fuel_information/fuel_info_home/ethanol/e10/ethanol_properties

 

[zogger]

So, are you gonna quit using ethanol contaminated fuel now, at least for the saws? Not sure how many gallons a year you use for sawmix, but..is it worth a little extra to not have issues like this?

I know it is for me, heck, I'll pay double to not run monsanto welfare fuel.

 

[GrassGuerilla]

Just curious, what saws are you seeing this problem with?

 

[pro94lt]

This has occurred alot with my 200ts and happened to my echo 360t back when that's what I climbed with. For this to happen it needed to be above 90 and the saws were being ran hard. My guess is 90% of saw owners won't run a saw hard when it's that hot... and I may have been running e10 back then it was before we understood how bad it was and I haven't had it happen the last 2 years if I remember right. Problem with the top handles is the muffler is right next to the fuel tank. What saw?

 

[pro94lt]

Oh and the fuel was actually boiling on the 200t what temp does it boil I wonder?

 

[Chris-PA]

So, are you gonna quit using ethanol contaminated fuel now, at least for the saws? Not sure how many gallons a year you use for sawmix, but..is it worth a little extra to not have issues like this?

I know it is for me, heck, I'll pay double to not run monsanto welfare fuel.

Well, I hate the whole ethanol scam, but it will pass soon. I will continue to get my fuel at the local station, which means E10 for now. This is the only issue I have with it, and I can deal with it as long as I understand what is happening. It only happens on really hot days anyway.

Just curious, what saws are you seeing this problem with?

Well, most recently was on the 42cc Poulan I just ported, but also on the various GZ4000 and clones, and the Earthquake G3800 clone. I think my McCulloch SE3420 (PM605) has also done it.

Really though, given the document I linked to I doubt that the saw design has all that much to do with it, other than if the saw gets exceptionally hot (like if it has a cat or something).

 

[CR888]

l don't know if this helps but l experience 'vapour lock' too occaisionally in a brushcutter l have. lt too happens after intense prolonged high load use. lt happens to some of my saws too.....but not all of them. For what its worth l have never ran E10 in anything l own as normal unleaded is readily availible, its actually hard to find E10 in Oz. lt usually happens after l switch off to refill gas and then won't start. The only way to restart unless you put it away till it cools down is to hold the throttle wide open and pullstart. This usually works restarting saws as well all though l don't recommend starting a saw this way as it can be a bit dangerous, but when you have work to finish sometimes you have little choice. lnteresting thread.....l am just not sold on ethanol being its cause, l believe its pressure buildup somewhere preventing fuel delivery.

 

[Chris-PA]

l don't know if this helps but l experience 'vapour lock' too occaisionally in a brushcutter l have. lt too happens after intense prolonged high load use. lt happens to some of my saws too.....but not all of them. For what its worth l have never ran E10 in anything l own as normal unleaded is readily availible, its actually hard to find E10 in Oz. lt usually happens after l switch off to refill gas and then won't start. The only way to restart unless you put it away till it cools down is to hold the throttle wide open and pullstart. This usually works restarting saws as well all though l don't recommend starting a saw this way as it can be a bit dangerous, but when you have work to finish sometimes you have little choice. lnteresting thread.....l am just not sold on ethanol being its cause, l believe its pressure buildup somewhere preventing fuel delivery.

Vapor lock is not strictly an ethanol issue, as it was a common problem in vehicles years ago. According to the document I linked to, ethanol in low concentrations with gasoline will increase the vapor pressure of the fuel, and it increases more with temperature than gasoline does. So it just makes it more likely to happen. 10% appears to be a bad concentration for this - at higher percentages the vapor pressure is reduced.

I've been able to coax them back with full choke and a bit of patience. The next time I have to cut in the heat I will just bring two saws and plan to swap them off each tank, giving more cool down time.