Author Topic: Vapor lock on a hot day.  (Read 555 times)

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Offline 3000 FPS

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Vapor lock on a hot day.
« on: June 29, 2016, 07:57:48 pm »
I went up to the mountains the other day to cut some beetle kill and it was pretty hot up there.   I took both of my Poulan 365's to cut with.

The first saw I cut down one tree and limbed it and then bucked it to 4' sections.   I went to start it and all it would do was start to run then quit.
I went to pop open the gas cap and the fuel just boiled out.   I let it calm down and then removed the gas cap and I could see the fuel boiling inside.
I figured from this that the fuel line was probably vapor locked.

So I fired up the other Poulan and after cutting another tree it started getting hard to start and same thing I opened the gas cap and I could see the fuel boiling inside.   I started making sure I set the saw in the shade which did help some and I was able to finish falling, limbing, and bucking up 4 more trees.     Anyone ever seen this before.    Just curious if this was because of the location of the gas tank on these particular models of Poulans or will they all do this in very hot weather.   
PP 505, 475, 445.

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Offline Cut4fun .

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Re: Vapor lock on a hot day.
« Reply #1 on: June 29, 2016, 09:07:17 pm »
Had my partner 5000 saws do this cutting in hot. Course they have metal tanks right on with crankcase though. Never seen my plastic tank poulans do it yet.
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Offline 3000 FPS

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Re: Vapor lock on a hot day.
« Reply #2 on: June 30, 2016, 12:49:38 am »
I think next time I go up I will try a Husky 455 and a Stihl 036 and see if they have any issues.
PP 505, 475, 445.

Offline Hoggwood

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Re: Vapor lock on a hot day.
« Reply #3 on: June 30, 2016, 06:30:19 pm »
I've had symptoms on one of my 3400's.  Maintaining tank pressure helps.  I know Homelite used to state that it was important to keep the pressure high in the tanks to minimize fuel boiling issues.  When refuelling the 3400 in hot weather I had to run it till it was empty, fill and fire up immediately.  If it sat fuel, would move back down the fuel line and it was a pain to get the pump pulling fuel again. 

Don't know if it were an issue with fuel boiling in the tank or more in the carb.  Is it boiling in the actual tank or out of the carb, line and filter? 

I gets really hot here as well.  I don't know if using cold fuel may help.  I've thought about pouring some fuel into 1 L pop bottles and putting them on ice in an old cooler.  Goofy idea perhaps. 
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Offline 3000 FPS

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Re: Vapor lock on a hot day.
« Reply #4 on: June 30, 2016, 10:03:21 pm »
You know Hoggwood I have not seen this before so I really do not know what to think.    But if the fuel is boiling in the tank then I would think that it is not doing much good in the carb or the fuel line.     All I really know is that I am taking some different saws next time.   I do not have time to be messing around with saws when up in the mountains trying to get some firewood.
PP 505, 475, 445.

Offline Al Smith

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Re: Vapor lock on a hot day.
« Reply #5 on: July 01, 2016, 05:20:08 am »
I think it was 1975 in the Rockies near Vale Co we had that happen to two saws .A Poulan S-25 and a little Pioneer .

It was cutting aspen for  stove wood on a deer hunting trip and it wasn't warm out in Oct .The saws cut okay they just boiled the tanks at about 9,000 ft elevation .We had to lean them out before they cut right .BTW I still own the Poulan and it still runs as good as the day I bought it.
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Offline 3000 FPS

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Re: Vapor lock on a hot day.
« Reply #6 on: October 29, 2016, 02:57:15 pm »
Looking back at this I think the fuel boiling was a combination of the altitude I was at, and the temperature that day.    I was up a lot higher than I usually go to and the fact that it was very hot that day created the right combination.
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Offline Eccentric

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Re: Vapor lock on a hot day.
« Reply #7 on: October 29, 2016, 03:44:22 pm »
I've only had one saw refuse to restart because of fuel boiling.  Was a Stihl 031 that I was running in 100deg f + heat.  I've heard/felt fuel boiling in the tanks of a few other saws (10-series Macs and old Homelites) in hot weather, but they still restarted and ran fine.  It's a bit unnerving though...
-Aaron

For older saws:
Tune the H side so that it 4-strokes (burbles) at WOT unloaded and just cleans up when under load.
When you lift cutting load, the saw should immediately revert to 4-stroking.  Fine tune the transition point for the wood you're cutting.
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Offline Al Smith

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Re: Vapor lock on a hot day.
« Reply #8 on: October 31, 2016, 07:57:46 pm »
Couple years ago in 96 degree August weather I was bucking two huge ash trees.Alternating between a 700 McCulloch and an 038 Stihl magnum .If I shut down to fuel the McCulloch I just as well wait 20 minuted before it would start .I really think it was more the ignition than vapor lock .Once it was started it ran just fine .The Stihl always started .

Me and a helper,6 cords,bucked split stacked .Not too bad for an old phart for a days work .--the beer was good too  after the work was done.
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Offline ms460woodchuck

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Re: Vapor lock on a hot day.
« Reply #9 on: November 02, 2016, 08:22:57 pm »
My favorite part...THE BEER!!

 

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