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Vapor Lock I Think


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#1 FixItCharlie OFFLINE  

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Posted July 09, 2017 - 01:18 PM

Last weekend I got my Ford LGT 100 back to the place where I use it. This is the tractor that I had replaced the rings in because of oil burn. I put on the mower deck & started mowing all seemed to be working very good but after about an hour it started acting like it is running out of gas & died. I checked the fuel level, it is about a quarter of the tank full. It would start to run with full choke but not for very long & not enough power to move the tractor. I let it sit for about 15 to 20 minutes went back & it started back up. So I closed it back up & started mowing again. This time it ran good for about 45 minutes to an hour & did the same thing, acting like it was running out of gas & died. Again let it cool for 15 to 20 minutes & it would run for 45 minutes to an hour with the same problem. This is the closed side Ford GT on my LGT 145 the fuel line runs above the carburetor so thinking this may help I moved the fuel line on the LGT 100 but it did the same only running for 45 minutes to an hour. The LGT 145 is an open side Ford GT. This is one of the problems that this tractor was having before it started smoking from burning oil so it makes me wonder if this problem may helped to cause the oil burn. Both garden tractor are gravity fed with the gas tank mounted above the engine. I did a tune up on both tractors last spring with new points, cap, fuel filter, & air filter. On the LGT 100 I changed the valve on the bottom of the gas tank. I have replaced the old fuel cap & I know that Ford in the manuals states that if the fuel tank cap does not allow enough venting this can cause a problem but the problem still occurs with fuel cap unscrewed so I do not think that is causing the problem. I have plans to put a vent tube into the fuel tank. Doing some research I find that ethanol fuels can cause vapor lock easier as they get older but the same age gas is being used in both tractors with the LGT 145 having no problems with this but it is open sided. An after thought is maybe try using the tractor without that side on it. The tractor is far enough away that I do not have easy access but maybe able to have some else try this. Last year when I was having a problem very much like this I was thinking something with the coil because it would come loose in its mounting but I changed the mounting & have no problem now with it getting loose. I am looking for ideas on fixing this problem. One thought is a fuel pump but do not know if this is the right way to go.

 

Charlie  



#2 gopher OFFLINE  

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Posted July 09, 2017 - 01:44 PM

Next time it does it check for spark. Some times when coil going bad seems like running out of gas. Make sure your not running lean making engine run hotter causing vapor lock.


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#3 GardnMastr OFFLINE  

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Posted July 09, 2017 - 01:51 PM

The requirement for good carburation is good valves. It is possible there is black varnish, technically "coking", built up on the exhaust valve stem and guide. After running 45 minutes, the clearance is reduced enough that the exhaust valve sticks open. Sometimes you can here a loud click when the valve cools down and slams shut. If during an overhaul the reamer is not run through the exhaust guide, the problem still remains. Larger Kohler engines need a 5/16 reamer.
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#4 FixItCharlie OFFLINE  

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Posted July 09, 2017 - 01:58 PM

I did not have my spark tester with me so I could not check for spark but it would run with the choke closed so if it is a spark problem it should not start. The high speed adjustment screw is turn out almost 3 turns as I was playing this adjustment when the problem was happening. The carburetor has been replaced as the original had shafts that seemed to be getting lose.

 

Charlie 



#5 WNYTractorTinkerer ONLINE  

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Posted July 09, 2017 - 02:14 PM

May have pulled some gunk into the carb..  Read the plugs..


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#6 FixItCharlie OFFLINE  

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Posted July 09, 2017 - 02:19 PM

No Machine Shop work has ever been done on this engine yet. It is standard bore & ring gaps are with in spec. This time when it was opened up I could find no play in the valves when they were open. My thought is yes it is getting close to needing to be torn down with complete machine work but when using the Manometer it was showing 5 to 10 inches of vacuum on the crank case at full throttle. I did not check crank case vacuum when it was hot like after running that long. At the end of this year when I retire & eventually get everything moved there that could be one of the test I definitely check. 

 

Charlie



#7 FixItCharlie OFFLINE  

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Posted July 09, 2017 - 02:26 PM

The spark plug is dark showing it is running on the rich side & timing is right on the mark. No knocking sounds are heard when it is running.

 

Charlie 



#8 Gtractor OFFLINE  

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Posted July 09, 2017 - 02:39 PM

Clamp some old style clothespins at several places on the fuel line. 

Don't know why but it will eliminate vapor lock. 

Theory is it works like a cooling fin and wicks heat away from the line.

Quicker-easier than rerouting the line.

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#9 dodge trucker OFFLINE  

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Posted July 09, 2017 - 03:06 PM

tank venting OK?   

i would still check and verify spark when it dies... might well be weak...

I had another idea (just happened to me within last couple of weeks) but if yours is gravity fed w/ no pump that rules  that one out...

how old is the gas line? Coming apart from the inside out?


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#10 GardnMastr OFFLINE  

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Posted July 09, 2017 - 03:39 PM

The order of failure is: First, ignition. Second, fuel. Third, compression. So____ verify you have blue spark right up to and including the time the engine is dying. You or I could make an engine run with a pump oil can with gas in it. It would be easy to supply fuel to the intake of the carburetor. 3rd no play in the valves has no meaning, if the exhaust guide is too tight from carbon. Did you grind the valves? Perfect exhaust valve color is tan carbon on top. Shiny steel color on a used engine exhaust valve indicates it is getting too hot and burning the carbon off its top. Exhaust valves get rid of their heat by transferring it to the exhaust seat.
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#11 stiemmy ONLINE  

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Posted July 09, 2017 - 03:54 PM

Clamp some old style clothespins at several places on the fuel line.
Don't know why but it will eliminate vapor lock.
Theory is it works like a cooling fin and wicks heat away from the line.
Quicker-easier than rerouting the line.

Please explain how this works to me. Wood is a heat insulator, not a heat conductor like a heatsink.

Edited by stiemmy, July 09, 2017 - 03:55 PM.

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#12 chieffan OFFLINE  

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Posted July 09, 2017 - 04:26 PM

Please explain how this works to me. Wood is a heat insulator, not a heat conductor like a heatsink.

I second that.  Bout like his battery revive?  :poke:         :rolling:


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#13 Gtractor OFFLINE  

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Posted July 09, 2017 - 04:58 PM

I don't know how it works but I've seen it work first hand several times in the last 40+ years.


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#14 stiemmy ONLINE  

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Posted July 09, 2017 - 06:07 PM

I don't know how it works but I've seen it work first hand several times in the last 40+ years.

Not tryin to be negative, but that is probably possible through thermal transfer, but wood is a poor conductor.

Maybe, its about cutting off the flow, or something similar to that. Fuel related blockage, or something with the ignition, or rerouting the lines.

http://www.jegs.com/...awlgRoCb-Dw_wcB

These are used between the carb, and intake.

Edited by stiemmy, July 10, 2017 - 07:53 AM.

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#15 gopher OFFLINE  

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Posted July 09, 2017 - 07:51 PM

Not tryin to be negative, but that is NOT possible through thermal transfer! Wood does NOT transfer heat!!!!!!!!!!!! Period.

Maybe, its about cutting off the flow, or something similar to that, but, it aint heat related. Fuel related blockage, or something with the ignition is where I'd start 1st.

http://www.jegs.com/...awlgRoCb-Dw_wcB

These are used between the carb, and intake.

Poor heat conductor yes,wood does not transfer heat wrong. My radiant heated hardwood floors feel pretty good on my bare feet in the winter lol. I've heard of the clip pins a lots of times but think more getting lines away from heat source then heat sink effect. 


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