Ask Paul: More on hot engine starts

Q: I’d like to offer my response to a hot engine start (What is the procedure for a hot engine start?). If I know I’m going to have a quick turnaround after engine shutdown, this is what I do: I throttle up to about 1,500 rpm, then I turn the fuel selector to off. By doing this, you use the fuel in the line and, when that is gone, the engine will shut off. This basically eliminates any vapor lock on restart, the typical cause for hot start issues.

Hot start procedures using this shutdown method should proceed as if the engine was cold. It’s worked for me countless times. Have you ever tried this method?

ANDY REINACH, via e-mail

A: Thanks for sending in your comments regarding hot engine starts. It’s always nice to get ideas from folks who have had success with things like this particular issue.

While you didn’t say, I assume you have a fuel-injected engine, which would make sense. Usually the problem of getting a hot engine to start is a result of the fuel boiling in the lines and evaporating while the engine is shut down following the flight.

The problem area is primarily between the fuel injector throttle body and the flow divider, which is mounted on top of the engine in most installations, and the fuel nozzles installed in the cylinder head. The fuel lines running between the two points are exposed to all that engine heat (remember heat rises), which increases following engine shut-down for a period of time, causing the fuel to boil and evaporate. The hard starting comes from not having any fuel getting to the cylinder when trying to restart the engine, which means you’ve got to do a lot of cranking to get the fuel where it needs to be.

By using your procedure, Andy, you simply begin like a cold start and prime or turn the boost pump on like you would for the first start-up of the day.

It’s hard to argue with success and, if this procedure works well for you, it should do the same for others.

Paul McBride, recognized worldwide as an expert on engines, retired after almost 40 years with Lycoming. Send your questions to: AskPaul@GeneralAviationNews.com.

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