AFP Purge Valve Operation

[Mike S]

Originally Posted by ronschreck

Mike, since you recommend

Not recommend, just a report of what I do.

Originally Posted by ronschreck

leaving the valve closed after engine shutdown it is implied that there you have no spring on the valve actuator arm to hold it open. This is a safety issue since failure of the cable attachment to the purge valve could allow the valve to close in flight resulting in fuel starvation to the engine. A return spring should always be attached to the purge valve actuating arm to hold it open.

There is a spring, and if the cable breaks off at the valve, it will keep the fuel flowing. The friction of the cable is enough to override the spring, keeping the valve in bypass mode when parked.

Good eye here, this is an important safety issue as you said, and is worthy of repeating. Thanks for catching that.

[erich weaver]

Hey Don

Curious as to why your procedures have the purge valve at ICO when cranking. Just a precaution to avoid flooding if the engine doesnt start right away? I dont do this and havent had any problems, but Im sure you have your reasons.

thanks

erich

[Don at Airflow]

Exactly. If the engine does not start there is fuel going in the engine, and when you stop cranking the engine driven pump continues to put one stroke of additional fuel in the engine. Fuel will be running out the intake. Not good

Don

[akschu]

Does the afp system use a prime pump like on a carb'd engine or is the boost pump the fuel primer?

[N15JB]

The boost pump provides priming.

Jim Berry
RV-10

[akschu]

So those that mean those that converted from carb to afp can use the hole in the panel that was for the primer for the purge valve? I just want to make sure I get this right on my panel drawing.

[David-aviator]

The only thing better than the purge valve is a cold beer.

Yes, on the former primer hole. A good place for the purge valve.