Backfire on starting

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AA5Bman

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He who ironically no longer flies an AA5B
When starting my engine (IO-470) I occasionally get a backfire right before it “catches” and starts. This is especially common when the engine is already hot. I have been under the impression this is probably mostly harmless, but not ideal.

Why does it happen, and is there anything I can do to avoid them?

FWIW my hot start procedure is the basic two-handed monkey pull: no prime, mixture idle cutoff, throttle full, start, add mixture until it fires, pull out throttle.
 
Well, then I'm not the only one that's happened to. :)

It will blow out some of the baffles in your exhaust system but you can decide how traumatic that is.

I tried every convoluted step and currently, I just crank the engine with no prime and if it needs a little help I give it a shot of primer while I crank with the mixture full, throttle cracked about half an inch.

You will get 50 answers from 50 people and the strat issue was incredibly frustrating for me. Eventually, most of my starting issues went away when I ditched my lightweight starter and went back to the Energizer boat anchor. I'm almost over Start Traumatic Stress Disorder.
 
Mag timing?
Over priming?
If you describe your start procedure, the group may be able to troubleshoot easier.
 
Lean mixture causes start-up backfire. Check your induction for leaks and/or find a better starting procedure
 
Stewartb said:
Lean mixture causes start-up backfire.
Click to expand...
Happens when the mixture is overly rich too.

Like the others, I’d be curious to see what your start-procedure is. Over priming and having some unburned fuel in the exhaust can certainly cause a backfire, which sounds possible since you say it typically happens when the engine is already hot.

The biggest issue is, chronic backfiring can crack the exhaust manifold and lead to CO entering the cabin.
 
He stated his procedure in the opening post.

To the OP-There's lots of Continental hot start info from good sources on the internet.
 
When it's hot, I start the 182 I fly by just cranking it with no prime. I have the mixture in full though. If it didn't crank, I would try pulling the mixture out.
 
Let me clarify: I may have gotten a backfire once or twice when the engine is cold, but for the purposes of this conversation, it really only happens with any regularity when the engine is hot.

I outlined my hot start procedure in the first post but it’s your basic no-prime, mixture idle cutoff / full throttle two-handed push/pull deal. For what it’s worth, the trouble is not getting the plane started, it’s that in this scenario I usually get a backfire.

PS - injected engine, IO-470
 
I mean... I'm not priming it at all on a hot start, and starting with at mixture at idle cutoff. I don't know how much more lean it can get...
 
AA5Bman said:
I mean... I'm not priming it at all on a hot start, and starting with at mixture at idle cutoff. I don't know how much more lean it can get...
Click to expand...
I hear that....so, what happens with a backfire?
 
I love a good backfire on start up. Makes the passengers laugh...

Even better when dark.
 
Here's a good read for big Continental FI guys. The simplified paragraph at the bottom of the page (Atkinson) is the best procedure I know. Omit running the fuel pump and it works on my Lycoming, too.

https://www.csobeech.com/hot-starting.html
 
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Have you checked your plugs? Not uncommon to have a cylinder misfire due to plug condition, then backfire when un-burnt fuel enters the exhaust. If it were me, I'd start with the simplest item first. Check plugs, then plug wires and then ignition timing.
 
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