Carburetor fire.

[the_novice]

Hey. I was driving my truck yesterday it's durasparked with a carb off an 82 thunderbird 4.2l. When it started to bog I pulled over and it died. I noticed fuel all over the top of the engine so I figured the clip on the float needle had come off. When I took the top off the carb the float, gasket, and little plastic surge bowl thing were melted and charred. My question is does anyone know how a fire could start in the float bowl? And would having a check valve on the float bowl vent have stopped it before it melted as much stuff as it did?

Thanks for any help.
Taylor.

 

[RonD]

I don't recall ever hearing or reading about that specific issue, carb fires yes, but not just limited to the float bowl.

The float bowl is vented, and if carb was warm enough gas fumes would be coming out the vent, but they would need a spark or some very hot heat source to ignite, maybe a backfire could do it, it would depend on where vent was located on that carb.
Once ignited the fire would follow fumes down the vent into the bowl, this would consume gas in bowl pretty fast, this would stall the engine.

 

[the_novice]

It's vented through the top of the carb inside the air cleaner so that makes sense. I thought it was vented from the top of the bowl. Anyway the carb is in for a rebuild now. Hopefully I'm done with the timing so no more backfires.
Thanks for the reply.
Taylor.

 

[wildbill23c]

Yikes, not very familiar with this problem, however it could have been very bad. Be glad the truck died you could have had a truck melted to the ground very easily.

 

[RonD]

In most of the carbs I have worked on the float bowl vent is in the air stream for engine.
I think the reasoning behind this is that if the float/needle valve were to fail and allow fuel to overfill float bowl the extra fuel would end up in the engine and cause a flood out.

If vent is just on the top of the carb and not in the air stream then the fuel would just pour out onto the intake and eventually be ignited by exhaust manifold/EGR valve or spark from leaking wire, this would cause quite a large fire because of the pooled fuel on the top of the engine.

 

[the_novice]

Yeah the truck has a new accessory. I bought a fire extinguisher.