Airfilter caught fire!! What the blithering heck! how?

[Shinnster]

Hey all, not sure if this should be in this section, wasn't sure where to put it!

Took my van to a friends today to check the compression, all done ok (well not ok but done what  I went for)
afterwards I took him for a quick blast down the road, literally about 5 miles max, and upon returning his missus pointed out there was smoke coming from the rear vent on the side of the van. Drivers side.

i quickly opened the engine bay to see smoke escaping from the air box.... I disconnected it taking it out and opened it to see what was occurring, only to see the air filter literally smouldering and burning through!!
took the filter out and it went up in flames pretty quickly!!
The burnt section was facing the pipe going to the rear vent, not the carb side.

what the hell could cause this? as now I'm a tad scared to drive the van!




 

[Aidan]

did somebody toss a lit fag into the vent ?

[davidoft1]

probably filled with fuel from turning over and not starting up

[Shinnster]

surely i'd be pretty unlucky to have that happen while driving?
i didn't see a butt in the airbox but guess I wasn't even thinking of that!

[Shinnster]

probably filled with fuel from turning over and not starting up

the airbox wasnt on when running the compression test

[Aidan]

is the airbox open to the engine bay or connected to the snorkel or rear intake ?

[Shinnster]

is the airbox open to the engine bay or connected to the snorkel or rear intake ?

its connected to the snorkel thing

[Shinnster]

after being scared by this and wondering how it can never happen again, does the air box have to be connected to the pipes going to the rear vent?  or can i just remove the small section of tube and have the air box getting its air from the engine bay?
i know this wont be cold / cool air so will that make a difference?

 

[DoubleOSeven]

Keep it stock. The air in the engine bay will be warm and although quite well ventilated it will affect performance. The forced air from the external vent is much better for it.

1, Most engine fires occurs from a spark from the carb., so that needs sorting. Check those x3 12V feeds. Solenoid, Autochoke, Carb. Heater.
2, But fires also need a source, the fuel ‘vapour’ ignites. Check your intake fuel line for any leaks, you need to track down where the vapour is coming from.

[DoubleOSeven]

probably filled with fuel from turning over and not starting up

^^ Agree, this happened. All that cranking during the compression test & not starting soaked the filter through the pancake. So, it’s just the fire ignition source to find.

[Shinnster]

Keep it stock. The air in the engine bay will be warm and although quite well ventilated it will affect performance. The forced air from the external vent is much better for it.

1, Most engine fires occurs from a spark from the carb., so that needs sorting. Check those x3 12V feeds. Solenoid, Autochoke, Carb. Heater.
2, But fires also need a source, the fuel ‘vapour’ ignites. Check your intake fuel line for any leaks, you need to track down where the vapour is coming from.

cheers for the input,
i have replaced all my fuel lines when I got the van so i'm pretty sure they are all ok.
as for the 12v feeds, i'll do some reading and see where i should be looking (my skills are less than zero lol)
 

[DoubleOSeven]

The 3 wires attached to the carb are the 12V feeds

[Mocki]

Did it back fire?

The nature of the beast is the airflow is going from the filter towards the carb, so the likelihood of anything going from the carb towards the filter while the engine is running is slim to none unless it was a explosion (Backfire)

Which way was the filter pointing ? Is the burnt bit nearest the carb or the fresh air intake ??

And yes you can get rid of the snorkel, I haven’t had one on my vans for twenty years , infact i have a kerosene tank in that void .

[Shinnster]

Did it back fire?

The nature of the beast is the airflow is going from the filter towards the carb, so the likelihood of anything going from the carb towards the filter while the engine is running is slim to none unless it was a explosion (Backfire)

Which way was the filter pointing ? Is the burnt bit nearest the carb or the fresh air intake ??

And yes you can get rid of the snorkel, I haven’t had one on my vans for twenty years , infact i have a kerosene tank in that void .

it didnt back fire, but there was some spluttering but i'd guess thats cause smoke was being pulled into the carb?

the burnt bit of the filter was directly inline with the fresh air intake. surely if it came from the carb it would have had marks on it (before it went up in flames) on the carb side?

[Mocki]

Yes, i agree, so it must have been an external force that ignited it , as spark or some such being pulled in the intake .