Jump to content

Nominations for Tractor of the Month
Garden Tractors and Parts on eBay



Photo
- - - - -

Vapor Lock


  • Please log in to reply
12 replies to this topic

#1 OLD HOUSEBOATER OFFLINE  

OLD HOUSEBOATER

    Member

  • Member
  • Member No: 5025
  • 1 Thanks
  • 19 posts

Posted July 29, 2011 - 06:15 PM

The mower is a Cub Cadet 2166 Hydro with a 16HP Kohler. I have gone bonkers nailing down the problem. Mows good then leans out backfires and quits. Went thru Carb, tank, fuel pump, cap vent, etc.

Found the problem today. The gas is boiling in the line between the tank and fuel pump causing vapor lock.

I'm going to reroute the line but really am not sure what is causing the problem.

What say you?

#2 IamSherwood OFFLINE  

IamSherwood

    Elf guardian

  • Senior Member
  • -GTt Supporter-
  • Contributor
  • Member No: 2066
  • 8,379 Thanks
  • 7,696 posts
  • Location: Northern Ontario

Posted July 29, 2011 - 06:39 PM

That sounds odd. I take it you have clear fuel line between the tank, and the pump? That's how you saw it boiling?
So, it over revs, back fires, and quits?
Have you got a picture of the fuel line routing?

#3 Ranchkingron OFFLINE  

Ranchkingron

    Tractorholic

  • Senior Member
  • Member No: 1613
  • 28 Thanks
  • 183 posts
  • Location: Michigan

Posted July 29, 2011 - 08:14 PM

I have to say that's a first for me also ?

The reason I say that is if the line is getting hot enough to boil the fuel it would also melt the line, on the older cars metal fuel lines would sometimes get hot enough (if run close to the block or exhaust manifold) to vapor lock but even then it was rare.

You say it boils between the tank and the pump ? I would think it would boil between the pump and carb, thats where the most heat is.

Are you positive you see boiling or are you seeing air bubbles ?

My guess would be it's some other fuel related problem i.e. a vacuum leak at the intake ?

Ron

#4 OLD HOUSEBOATER OFFLINE  

OLD HOUSEBOATER

    Member

  • Member
  • Member No: 5025
  • 1 Thanks
  • 19 posts

Posted July 29, 2011 - 08:40 PM

Pulled the line off at the pump INLET. Gas Boiled and burped for almost 2 minutes.

Didn't believe it. Put it back on and mowed for 10 more minutes. Identical thing happened.

I read these threads and it comes up once in awhile that mowers will run for 15 or 20 minutes and quit. They start up and run for awhile and quit again.

I wonder if this is the reason.

I've been working on these things for over 50 years and never ran into this before.

I'm going to change out the hose and route it away from the hydro.

#5 MH81 ONLINE  

MH81

    Proud to be Deplorable

  • Staff Admin
  • Staff
  • -GTt Supporter-
  • Contributor
  • Member No: 802
  • 27,325 Thanks
  • 28,640 posts
  • Location: N. W. PA

Posted July 29, 2011 - 09:31 PM

Is the hydro running that hot? Wow! How's the cooling fins & fan?

Edit: Got to thinking... if the line is pressurizing because of gas boiling in the lines... the pressure should be going in to the tank & releasing there too. If the tank isn't releasing the pressure, it would build up and continue to blow off once you stopped. it would also force more gas into the carb. If you would do one more thing before rerouting, loosen the vent cap (I know you already worked on it... ) and see if it runs longer. The gas may still be vaporizing in the lines, but it should equalize both directions.

The other thing you could do is wait until it quits and carefully open the cap. watch if it has pressure, you don't want it releasing in a hurry. Especially if your gas tank is under the hood.

if the line is getting hot enough to boil the fuel it would also melt the line


Actually, gas has a pretty low boiling point. Depending on mixture, chemical wizardry & Ethanol %age, as low as 100, and as high as 400 degrees F. If you buy your gas at store X... might want to try brand Y once. Just to see if the different brand is a culprit too.

Edited by MH81, July 29, 2011 - 09:51 PM.


#6 Ranchkingron OFFLINE  

Ranchkingron

    Tractorholic

  • Senior Member
  • Member No: 1613
  • 28 Thanks
  • 183 posts
  • Location: Michigan

Posted July 30, 2011 - 12:32 AM

Is the hydro running that hot? Wow! How's the cooling fins & fan?

I didn't even think of that you're right if the line is really close to the hydro it could pick up heat.

Edit: Got to thinking... if the line is pressurizing because of gas boiling in the lines... the pressure should be going in to the tank & releasing there too. If the tank isn't releasing the pressure, it would build up and continue to blow off once you stopped. it would also force more gas into the carb. If you would do one more thing before rerouting, loosen the vent cap (I know you already worked on it... ) and see if it runs longer. The gas may still be vaporizing in the lines, but it should equalize both directions.

True it very well could be a clogged fuel cap.

The other thing you could do is wait until it quits and carefully open the cap. watch if it has pressure, you don't want it releasing in a hurry. Especially if your gas tank is under the hood.



Actually, gas has a pretty low boiling point. Depending on mixture, chemical wizardry & Ethanol %age, as low as 100, and as high as 400 degrees F. If you buy your gas at store X... might want to try brand Y once. Just to see if the different brand is a culprit too.


True it does 100-400 degress F. but the way the OP worded the problem I assumed the fuel line was clear i.e. Tygon or Vinyl how else could he see the fuel boil in the line ?

Both of those have a heat fail point of 160 degrees and some hydro temps can reach that, more if the fan is gone and/or the cooling fins are filled with debris like you said.

I'm wondering now if it could be a combination of problems fuel tank cap, heat from the trans or ?

Does this engine have a fuel return system ? I have heard some of the newer ones do, or possibly the fuel pump has failed and is sucking air.

Ron

#7 OLD HOUSEBOATER OFFLINE  

OLD HOUSEBOATER

    Member

  • Member
  • Member No: 5025
  • 1 Thanks
  • 19 posts

Posted July 30, 2011 - 06:23 PM

Resolved

The muffler was split and the heat shield pushed the heat right down the frame rail

#8 Ranchkingron OFFLINE  

Ranchkingron

    Tractorholic

  • Senior Member
  • Member No: 1613
  • 28 Thanks
  • 183 posts
  • Location: Michigan

Posted July 30, 2011 - 06:40 PM

Resolved

The muffler was split and the heat shield pushed the heat right down the frame rail


That's great to hear glad you found the problem so how do you plan to fix it, new muffler ?

Ron

#9 IamSherwood OFFLINE  

IamSherwood

    Elf guardian

  • Senior Member
  • -GTt Supporter-
  • Contributor
  • Member No: 2066
  • 8,379 Thanks
  • 7,696 posts
  • Location: Northern Ontario

Posted July 30, 2011 - 07:33 PM

Well, that was an easy fix.
See, collectively, any problem can be solved.:D

#10 MH81 ONLINE  

MH81

    Proud to be Deplorable

  • Staff Admin
  • Staff
  • -GTt Supporter-
  • Contributor
  • Member No: 802
  • 27,325 Thanks
  • 28,640 posts
  • Location: N. W. PA

Posted July 30, 2011 - 07:49 PM

Resolved

The muffler was split and the heat shield pushed the heat right down the frame rail


Wow, I'd have guessed all day.
Thanks for the info, I'll put that in the "Things you should remember" category.

#11 caseguy OFFLINE  

caseguy

    Connoisseur of Rusty Junk

  • Senior Member
  • -GTt Supporter-
  • Contributor
  • Member No: 906
  • 1,624 Thanks
  • 5,600 posts
  • Location: Edinburg, PA

Posted July 30, 2011 - 08:38 PM

Glad that you got it figured out! I'd never have guessed that one either! Duly noted and stored in the archives! Thanks for the update!

#12 KennyP ONLINE  

KennyP

    FORDoholic

  • Super Moderator
  • Staff
  • -GTt Supporter-
  • Contributor
  • Member No: 2253
  • 28,518 Thanks
  • 39,735 posts
  • Location: Collinsville, Oklahoma

Posted July 31, 2011 - 04:35 AM

Glad that you got it figured out! I'd never have guessed that one either! Duly noted and stored in the archives! Thanks for the update!


I have to store things on the computer. The old 'archives' are stuffed with too much useless things. Glad you found the problem and it was something very simple. I'd still reroute just for future piece of mind.

#13 OLD HOUSEBOATER OFFLINE  

OLD HOUSEBOATER

    Member

  • Member
  • Member No: 5025
  • 1 Thanks
  • 19 posts

Posted July 31, 2011 - 08:43 AM

Going to fix the muffler and foam the end of the frame.




Top