Hot starting troubles

[hisoos]

I had a well crafted long winded post prepared and lost it so here is the short version. Why does my plane not want to start after it just started and ran fine just as much as a few minutes ago. Yesterday it was a trip from the hangar to the pumps which resulted in about an hour hanging out on the tarmac and some very sore muscles today. I've had this plane for 22 years and feel like I know most tricks of the trade when it comes to these old planes (46 BC12-D C-65) I tried everything I know. It usually just means letting it sit, cuss at it, and wait until it decides to play nicely. Cold starts, no problem. Run it or fly it for a short amount of time and plan to possibly be there a while. It did it again today even though I felt it had rested plenty long enough. I gave up in favor of beer to ease my aching muscles. Almost lost it once to a big storm coming in and no where to tie down.

Anyone know the cause or trick to this? Otherwise she starts and runs fantastic.

[hisoos]

Ohh and I searched for a while, didn't find what I was looking for. Feel free to point me to an old post on the subject. Just fed up with this issue. Getting older now, sore muscles, and short on patience.

[3Dreaming]

What magnetos do you have?

[hisoos]

Eiseman

[hisoos]

Recently refurbished somewhat. Points, rotor, condenser, and if memory serves me correctly, coil in one of them.

[beaverbill]

I had an Aeronca Chief once with a similar situation. The trick was to shut down the engine by turning off the fuel and let the engine die from fuel starvation. Then leave the fuel off for the next engine start. After the engine started there was time to run around to the cockpit and turn the fuel back on. I don't know why it worked that way, but the previous owners told me about it. And that was their technique, and it worked. A-65 with a Stromberg carburetor as I remember.

[hisoos]

Bill, perhaps I misunderstand. If the fuel remains off after shutdown and start-up, how would it start with no fuel (assuming dry bowl and/or vacuum). Or do you imply turning the fuel on long enough to fill the bowl, then off before starting?

Thanks for the reply.

[beaverbill]

No, just leave the fuel off. I have no idea why it worked that way. But it did on that plane. Believe me, I tried all the other usual ways to start and was unsuccessful. I don't know if this is the answer in your case. But if nothing else works, give it a try. I should mention that on that Chief the first start of the day was done using normal procedures. Subsequent shutdown and restarts required tuning the fuel off. Counter intuitive for sure, and unfortunately I didn't fly that plane long enough to really figure it out.

[3Dreaming]

There are two things an engine needs to run. The correct fuel to air mixture and a good spark from the ignition. It sounds like you ignition should be okay, but everything should be suspect. My guess that something might be slightly plugged in your carburetor. They have many small passages. How you shut down the engine can help with starting. There is an instruction from Continental to open the throttle as you shut down the engine to lean the mixture, this is for the Stromburg carburetor. Doing this will help. Also, in my opinion starting slightly above idle will help when hot. Our airplane we have to open the throttle to start when hot. we have used as much as half throttle before. We have the old Bendix mags without impulse couplings. With 2 people it is not an issue. My son flies quite a bit by himself, and starting hot by himself requires a different technique. He sets the throttle for 1100 RPM, and shuts down. He then starts without touching the throttle. The parking brake is always set and the tail is always tied down if there is no one to help with starting. Also unless we know the person we don't let anyone else prop the airplane hot, because they do not spin the prop fast enough, (no impulse).

[Ralph925]

When mine is hot I need to be very careful to not flood it when starting. I turn my fuel off while it is parked and don’t pull it through when hot, just turn the mags on and give it a go. If it does not start, I turn it backwards 8 blades with the mags off then try again. Your problem may be different but the advice is fully worth the cost.

[otrcman]

"Recently refurbished somewhat. Points, rotor, condenser, and if memory serves me correctly, coil in one of them."


My understanding is that the NOS condensers are now pretty old and tend to deteriorate simply with age. Thus a New-In-Box condenser is sometimes unusable. It might be worth your while to find a resource where the condensers can be checked for proper function. Heat is not your friend when it comes to condensers.

Another option would be to put a different magneto on your engine and see how that works.

The fact that special care needs to be given to fuel mixture for starting is often a sign of weak spark and not a sign of carburetor problems. As the spark gets weaker you simply nead a perfect mixture to get the engine to fire. And that leads people to think they have a carburetor problem.

Dick

[hisoos]

Thanks for everyone's input. A couple of new tricks to try, and concerns to looks into. I have wondered about running the prop backwards. I used to do it as I was told by an old timer a long time ago, then somewhere along the line another IA told me it was not good. Can't recall the reasoning, but for some reason I thought it was something to do with running the mags backwards. Perhaps with impulse which I have. Either way, I don't think it is a flooding issue, so not sure that applies here, but the mags concern me as well as mixture.

I did take it for a quick hop today and pulled the fuel to shut it off just to see how long it took. It seemed to take for ever to die. I would hate to have to do that every time.

[Mark Bowden]

Does your carb drip gas when off or after you stop? Even though your mags were redone, doesn't mean they are "right".

Yes, it takes a while when you shut off the gas as it has to "run out". You can get the timing down when you taxi to your spot or back to your hangar with practice and will run out when you pull up. No big deal. You can tell it is just about to run out as rpm increases slightly.

When hot and I'm just getting gas, I do as Tom and the manual states, gas off, mags off, open throttle all the way as it dies. Even so given the minute or so it take to run out of gas it is still being drawn in as the motor spins down with this method. To reiterate what Tom mentioned, Strombergs are engineering marvels for their time but complex and have known float needle issues. They have multiple tiny off idle passages that serve as an accelerator pump.

I never prime when restarting hot and only pull through once maybe twice to get a good compression feel. The more you monkey with it hot the worse it gets.

I also never ever taxi to the pumps to gas up when leaving cold, I'll be sitting or an hour, this is way worse for me than a hot try at any temperature.

Turning the prop backwards is viable, make sure the mags are OFF.

I have also used the tie the tail, chock wheels, parking brake (don't trust it) and 1/3+ throttle. If it lights off it is scary.

Mine loves to start cold, and I'm sure I could use a rebuild as I know it hasn't been done in 21 years and likely never done ever. My mags are impulse and a year old. It has behaved this way since I was a kid.

[N96337]

When mine is hot I need to be very careful to not flood it when starting. I turn my fuel off while it is parked and don’t pull it through when hot, just turn the mags on and give it a go. If it does not start, I turn it backwards 8 blades with the mags off then try again. Your problem may be different but the advice is fully worth the cost.

This is exactly what my 85 required. Closed throttle and turn the mags on, flip it and it'll go.
John

[Edwin Otha]

Assuming you have no mechanical issues, when starting and you prop forever with nothing happening, the engine is too rich. Open the throttle and turn the prop backwards 8 or ten blades, if the engine kicks back and reverses it's too lean prime some more.

EO