FI ? When do you bypass fuel and for how long

[Tumper]

For you guys with fuel injected engines and fuel bypass valves, when do you use the bypass and for how long do you open it.

More specific how hot is the engine when you use the bypass (when you taxi to the fuel pump?after a long flight?or just on a real hot day)? And, how long do you bypass fuel?

[flynwest]

Use it to cut off engine. When hot starting open throtle full and run purge valve 45 seconds. My hot start is while the purge is still pulled and the electric pump running with throtle at about 1/4 open engage starter and then slowly push in the purge valve. Works for me.

[JDanno]

as I recall the Airflow instructions for a hot engine is to 1/2 throttle and close mixture with purge valve open for 20 to 30 seconds. Then close purge valve. Crank engine and slowly move mixture open until engine starts. Starts almost immediately every time. Retard throttle.
Those purge valves are the slickest thing for starting engines that are notoriously hard to start when hot.

[Tumper]

I know the procedure...what I'm not sure about is the definition of hot.

[eddieseve]

Engine start and taxi for fuel top up before flight I would class this as a warm engine, no need to use the purge valve. 1 sec on the fuel pump with the mixture open, then carry out a standard start.

Hot, just landed after a flight, taxi for fuel, shut down, fuel in the spider boils, you attempt a restart and the engine can then typically be hard to start, this is where the hot start purge valve procedure can help.

Cheers