Q: I have a Grumman Yankee Model AA-1 with a Lycoming O-235L 108-hp engine. What is the procedure for a “hot engine” start? When I shut down the engine, I run it lean at 1,800 rpm for about 10 seconds before I pull the mixture. Then, when the engine is cold, it starts right away. However, if I stop to refuel on my way to the hangar, it is very difficult to start and I don’t like cranking for a long time for obvious reasons. Would you be kind enough to advise me as to the proper procedure?
CARY MATHIS, via e-mail
A: Cary, this subject usually causes me to ask more questions about specific situations before I even attempt to provide an answer. I’m somewhat at a loss because you didn’t provide your engine age or history, which may provide a few clues, but let me throw out a few thoughts on the subject to see if they might help.
First of all, I’d recommend you review the airframe manufacturer’s Pilot Operating Handbook (POH) for specific “hot start” procedures. These, as well as normal starting procedures, may vary from aircraft to aircraft, making the POH the best source of information for any specific aircraft. However, some of the POHs may not explain why certain procedures are used in the starting process.
Your shut down procedure is fine and should cause no problem in restarting the engine.
You failed to detail the starting procedure when the engine is hot, but let me offer some thoughts. Since the engine has been run and is probably close to its normal operating temperature, you may not need to prime it. However, if you feel there is a need to prime the engine, it can best be accomplished using the primer system versus the throttle.
This brings up another question: Is your engine equipped with a carburetor that incorporates an accelerator pump? Not all O-235-L series engines have them and this, again, is airframe manufacturer specific. If your engine does have an accelerator pump, then this may be used to prime the engine by pumping the throttle two to three times from idle to full open, then back to 1/4 throttle while turning the engine through using the starter.
You must use caution because excessive priming using the throttle may cause flooding of the carburetor and airbox, which could result in a fire in the induction system. If you suspect there is flooding, then open the throttle and close the mixture and turn the engine over several times with the starter to clear it, then begin again with a normal start procedure.
There are a few more things you may also consider just in case they have not been checked recently. Check magneto to engine timing and spark plug condition and gap. Is there a possibility that the magnetos are not of the latest configuration? I’d suggest you ask your maintenance facility to research any and all Service Letters, Instructions, and Bulletins that may apply to your magnetos. Another thing that comes to mind is Lycoming Service Instruction 1068A and its Supplement No. 1, dated March 17, 1997, regarding tappet clearance, which is often overlooked but, none the less, important for the O-235 series engines.
I also recommend you contact the Grumman American Yankee Owners Group at AYA.org to see if other owners have experienced the same condition. An organization like this can be a wealth of information and, since I believe you are not the only person to experience this, the answer may be one e-mail away after contacting this group.
Hopefully, this will get you “started” and it will end up being something simple that may have been overlooked.
Paul McBride, recognized worldwide as an expert on engines, retired after almost 40 years with Lycoming. Send your questions to: AskPaul@GeneralAviationNews.com.