Originally Posted by
EXDAC
No one has yet supported the claim of increased fire risk.
Well the document you referenced mentions it, but not under the conditions later specified (warm OAT, max 3 pumps while cranking). The point is priming with the throttle has additional risks which should be considered, not dismissed.
EXDAC why don't you try a simple experiment: The next time you have your cowl off in cold weather, pump the throttle twice and then watch the fuel running out of the air box. I think you will then understand how much fuel is being delivered and where the fire will be.
Like I said there is no database of carb fire incidents that we can analyze to
prove the increased risk. You just have to understand that
- Your technique can lead to a pool of fuel in the intake system
- During a failed start attempt hot combustion gasses can end up in the intake system
- When you combine fuel, air, and an ignition source, you get a fire
The primer system on our O-200 pumps the fuel into the air intake (the cylinders have no primer ports) so the risk is similar. The primer nozzle atomizes the fuel better though so less fire risk due to less pooling. Maybe next oil change I'll make a video of how much fuel ends up in the air box with each technique.
PilotDAR, do you have any pictures of the damage from your carb fire? Did you take the carb apart yourself or just send it out?