Author Topic: Vapor lock?  (Read 265 times)

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Offline Jholley

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Vapor lock?
« on: December 16, 2013, 01:02:16 pm »
I changed the fuel lines on my craftsman 18" chainsaw and now my saw will run for about 2 minutes then die out and the only way I can get it to restart is to losses the fuel tank cap for a few second then tighten it back up. Then it will run for another 2 minutes. Did I mess up changing out the fuel line? I made both line going into the tank long enough to reach the bottom.  I know there was a fuel filter on one but I never saw a valve for the other.

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Offline 660magnum

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Re: Vapor lock?
« Reply #1 on: December 16, 2013, 03:38:40 pm »
There is also a tank vent which may be actually in the cap?

If the vent is plugged, you will draw a vacuum in the tank and eventually shut the engine down.
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Offline Moparmyway

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Re: Vapor lock?
« Reply #2 on: December 16, 2013, 08:03:13 pm »
Vapor lock is usually associated with warm temperatures. The gasoline tends to flash into a vapor from excessive temperatures while it is still in the lines. OAT's over 85-90 and lots of close to the ground stumping are usually the main culprits.

Unless you are running a winter blend of fuel in the summer, then it doesnt take much with todays cold weather blended fuels to vaporize on you while in use.

If you can open the cap and restart it - then 660magnum has nailed it !!

Offline 3000 FPS

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Re: Vapor lock?
« Reply #3 on: December 16, 2013, 08:45:47 pm »
Sure does sound like the gas tank vent to me also.
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Offline KilliansRedLeo

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Re: Vapor lock?
« Reply #4 on: December 17, 2013, 12:20:34 pm »
+1 on the tank vent!
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Offline fordfairlane78

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Re: Vapor lock?
« Reply #5 on: December 18, 2013, 06:23:49 am »
It does sound like the vent but also does this saw use a primer bulb? If so are you sure you have all your lines going where they should?  The line with the filter should go directly to the carb lower rh side and the primer bulb should pull fuel through this line into the carb out the lh side through the bulb and back into the tank. The return line from the bulb does not have to be long enough to get down into the fuel just into the tank...
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Offline 3000 FPS

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Re: Vapor lock?
« Reply #6 on: December 18, 2013, 01:08:09 pm »
It does sound like the vent but also does this saw use a primer bulb? If so are you sure you have all your lines going where they should?  The line with the filter should go directly to the carb lower rh side and the primer bulb should pull fuel through this line into the carb out the lh side through the bulb and back into the tank. The return line from the bulb does not have to be long enough to get down into the fuel just into the tank...

That is a good place to look.

The fuel line with the filter goes to the top right of carb.
The fuel line on the short connector of bulb goes to the bottom right of carb.
The fuel line on the long connector of bulb is the return to the tank.
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Online Philbert

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Re: Vapor lock?
« Reply #7 on: December 18, 2013, 04:45:51 pm »
I like Fordfairlane78's idea because it sounds like the problem started when you changed the lines.

Philbert

Offline weimedog

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Re: Vapor lock?
« Reply #8 on: January 12, 2014, 05:59:02 pm »
If not the tank vent, then it would be the pulse tube, and if it like the Husqvarna Poulan's it will be that pulse pipe grommet.

 

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