Fuel Boiling Hot

[KE4AVB]

What have some of the techs here use to shield a fuel line and fuel?

I got kinda a unique problem with a Kohler Courage on a Troy-Bilt. Mower is fine until operator stops and idle the engine while picking up sticks. When he does this the fuel starts boiling in the filter causing problems. I relieved it somewhat but think needing to install some heat shielding to keep heat away from the line. I personally used the mower and have verify is what going on. First I thought it just because the line was touching the engine which was part of problem moving away hasn't completely resolved the problem. I have verify the engine cleaned of all debris so air flow doesn't seem to the problem engine, Just too hot under the hood.

SV620-3212
13BX79KT011

Thought of trying AC line thermal insulation shield tubing.

[bgsengine]

Might not be the engine but the hood ducting - some hood designs do not lend themselves well to cooling the engine area and others may have missing pieces (air dam over the engine, foam insulators, etc) or missing muffler heat shielding 0r some other modification or accessory blocking air flow through the engine compartment. One could probably also *create* some modifications to air flow patterns to change air flow (maybe block something off to get air flowing IN across the fuel line from outside?) but it does require a little study of the whole engine compartment and a little understanding of aerodynamics and passive (as opposed to fan drive active) air flows may help

[38racing]

you say he lets it idle when picking up sticks. if I get off my mower with it running I keep it running at full rpm to keep it oiling and cooling.

[KE4AVB]

Hmmm, Looks like if I get time this weekend go over and sit with the mower studying things. At least it better than it was.

[hanz63]

Ever notice on the occasional walk behind that shears the flywheel key, though still runs up reasonably well - that it is running hot? Maybe just maybe this is creating a hotter environment there as well. It would be worth checking the key, cooling fins and armature gap. Have you taken a temp?

[KE4AVB]

Actually just got an IR temperature gun for that very purpose. This first time I ever ran into this on a small engine. Several of the old V8 's heat riser that gave me fit with vapor lock. Similar porblem as the fuel boils than nothing nothing but fuel vapor reaching the carburetor. Fuel in the fuel looks just like water boiling in a sauce pan on the range.

[Arkie]

Boiling fuel. Another good place to test with a IR thermometer. ambient temp around the fuel line.

I use one quite often. electrical, mechanical, A/C,

[38racing]

Ever notice on the occasional walk behind that shears the flywheel key, though still runs up reasonably well - that it is running hot? Maybe just maybe this is creating a hotter environment there as well. It would be worth checking the key, cooling fins and armature gap. Have you taken a temp?

interesting. last year I had a key shear on a briggs 31 series on a rider. this year I find it has bad afterfire at shutdown even with the ABS. Even letting it idle a bit still gives some pop. may I need to check the key again.

[KE4AVB]

Oh well I got my work as I got to create base line temperature chart from a known good TB Horse and then compare things to this one. Was hoping someone had ran into this. I see if I can find my old hot rod notes too, hopefully I pack them when I moved.

[KE4AVB]

Learning some interesting things reading this morning that I have forgotten. Like gasoline can boil everywhere between 100F to 400F and that our blended fuel can be any where between these two points. It also makes a difference if the fuel is a winter or summer blend as a winter blend has a much lower boiling point. Ethanol added also lowers this boiling point and with them going to a 15% ethanol blend here that might be part of my problem.

This is not as noticeable on a fuel system that uses a fuel to pressurize system as this raises the boiling point. Probably not even noticeable on a fuel injected engine. So there is two additional possible solutions I can look into now. One is convert the carburetor to fuel pump version and add a fuel pump. Another is to insulate the fuel line and filter. Of Course I still check on the air flow, that will me finding a suitable fuel source for my smoker so I can see the air flowing around in the engine compartment.