Boiling Fuel

[outdoors4evr]

I worked my 184 really hard for an hour mowing a field. There was a lot of chaff flying and I had to clean off the grill a couple of times. When I was done, we (the tractor and I) needed a bath. Shut down and heard the gas tank venting out (no fluid). Curious, I cautiously and slowly opened the lid (not wanting to burn down a tractor) and saw the gas in the tank rolling like it was boiling.

Anyone else experience this?
Am I missing a heat shield or something to prevent this? Tractor did not complain about the hard work or heat.

[gitractorman]

I've worked these tractors pretty hard and never experienced this. That's actually pretty scary! Do you have the white side shields under the front of the hood, along with the red side shields under the gas tank? Without the shields in place, you may be loosing some flow of air through the engine compartment. Also, I'd double check that your radiator is clean and there's good air flow through it. Fuel does boil at a lower temp than water, probably around 150F, but that's still pretty hot for a gas tank.

[Jim Becker]

Make sure you don't have an exhaust leak blowing towards the gas tank.

[BigBill]

What he said/\. Check the exhaust and the gas cap vent.

[Larry B]

Sounds like the fuel in the fuel line heat soaked from the stopped engine and boiled in the fuel line. Gas will boil around 200 degrees F. If you ran it hard for quite a while and shut it off hot this can happen. If you got the tank itself hot enough to boil fuel the engine would probably be glowing LOL.

[John *.?-!.* cub owner]

I was just getting ready to post about the same thing as Larry when I saw his post. I had a standard cub do that when I made a steel fuel line for it and trying to make everything look nice and neat I dressed it too close to the engine. Needless to say, I made a new line with different bends.

[outdoors4evr]

I didn't dare stick my finger in the tank to see if the liquid was hot. The fuel was rolling like a 1" tall geyser just forward of the fuel neck. I didn't see any bubbles, but I am pretty sure they were present which had the fuel tank venting air pressure (and probably fuel gasses).

To answer some questions, I do have the white panels by the radiator and the red panels covering the PTO area installed on the tractor. The exhaust goes forward in the 184 and is not routed anywhere near the carb or the fuel tank. The exhaust does not have any leaks and I wouldn't expect to see this as a heat source for the gas tank.
As mentioned, I did have to clean the grill a couple of times as this got blocked by chaff. I'm sure that the engine was warm as I was working the tractor hard, but it didn't spew coolant or show any signs of overheating at all.

[Landreo]

It is unlikely the gasoline in the tank was boiling but more likely the gasoline in the fuel line was boiling. It is near the exhaust manifold. However, the tank is over the exhaust manifold and engine so It may be possible the gasoline in the tank got hot enough to boil. Unlikely since the fan is blowing in that area but it may be possible.

I have many thousands of hours mowing with the numbered series and have never noticed any boiling so you may want to check the routing of the fuel line. Gasoline will boil at a low temperature but that area should not get hot enough for the fuel to bubble in the tank or in the fuel line.

[Greg Armstrong]

I experienced this today in the midst of mowing 5 acres. I opened the cap to check my fuel level and saw some bubbling. I rocked the tractor back and forth and it bubbled a little more... was coming from the outlet to the bowl. I felt the tank and it was not too hot to touch, and neither was the fuel line. It seemed more like air bubbles that you would see in a water cooler rather than "boiling", like sucking air up from the carb.

Also, my spine is feeling all five acres, why no springs on these seats??

[mozer71]

Spring forward, fall back. I haven't dumped my 154 yet and glad that I haven't. It is no fun getting out from under a Jacobsen or even a heavy Sears mower tractor. My 154 doesn't have the seat interlock/ kill switch so I stand up at times to survey what is ahead. Mine doesn't need a spring as the seat is a cushion to my brain on occasions. Part of it anyway. I often think about launch method on even smaller tractors. Ditches vary over time and weeds disguise where the boundary is. I've been upside down a few times with lighter mowers and it aint fun getting out. They were only 300 lbs. but when you are trapped into a crevice, be glad the engine stopped. Soaked with gasoline etc grabbing anything to lift it off- burning my arm .. This Can't happen but it has.

[mozer71]

Rare occasions sure. No matter. I might have the deck off the 154, linkages hanging ... The little fellow can't sit upside down in a ditch. Tow it right out with the 154.
How does this relate to "boiling fuel" ? I think that has been solved by previous posts. What can happen, unforeseen with a hot engine. In refueling the 154, very often if sloppy, fuel drips over the tank and goes 3 ways. It hits the main deck pulley belt. It can puddle even a small amount upon the flat head engine with the spark plugs right there. VERBOTEN! No way!
Dang it did happen and there were many plastic fuel tanks. Different threaded necks, back then. Worked fine for a while and it is chugging, Vent cap was plugged, pulled that screw out and fuel went quick and all over the gas tank, the engine...Moron
You can bet there was hour of drying/cleaning time before it was safe to start.
I think it liked it . It was like, hey you are wiping off all the dead grass mixed with gasoline. Ran nice.