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Today's engine puzzler #2

rv6n6r

Well Known Member
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I was inspired by David Harris's recent puzzler -- and who doesn't love Click and Clack? Here's my engine puzzler. Probably an easy one but I'm posting because it stumped me for a while, and perhaps some other engine-challenged folks like me can get some benefit. At the risk of getting beat up like David did, I'm not going to post the answer right away. But it will be later today or tomorrow, or as soon as someone gets it. If you're frustrated by that you can subscribe to this thread and you'll get the follow-ups in your inbox.

So here's the setup: at around 1400 hours the engine began having a hard starting issue. Mostly it would start right up but maybe 1 out of 10 times it would just crank and crank. I could get it started with some starter fluid (I know, not safe, but it did the trick).

This is an RV-6 with Lycoming O-360 A1A, cabureted, P-mag right side with aircraft ignition harness, traditional magneto left side, iridium lifetime plugs all around. I had the magneto serviced, adjusted the carb, checked the fuel screens & verified no water in the fuel, cleaned & gapped the plugs. Checked all ignition wires with no problems found. No change.

Then I listened to an EAA webinar by Vic Syracuse. Bingo!

The clues are there, if you know the answer write it on a set of James Aircraft RV-6 high speed fiberglass pressure recovery wheel pants and send it to me PO box [etc.] OR post it here :)
 
Bad ignition key switch?
Don't have that either, just a starter button and two mag switches (actually a grounding mag switch and a P-mag switch). All working good.

Again, the clues are in my original description, not in any component I didn't mention.
 
Plug Problem?

Do the Irdium plugs have screw on ends for the plug wires to attach to? I would believe that could cause that issue. Although you stated a convention mag on one side so that couldn’t be an issue for those plugs.
 
He mentions that a spray of starting fluid will make it start, so I?m thinking the electrical and ignition systems aren?t the problem. I?ll guess that the carb bowl is draining out somehow..
 
He mentions that a spray of starting fluid will make it start, so I?m thinking the electrical and ignition systems aren?t the problem. I?ll guess that the carb bowl is draining out somehow..

I agree, fuel problem. I?d guess a stuck needle valve (once engine starts with starter fluid the vibration frees the valve).
 
Starts with starter fluid, so likely not electrical.

Starts with extra fuel added, so likely too lean.

My guess is in intake leak. Old intake gaskets or hoses?

Aaron
 
Well it's time for the solution to this week's puzzler. Some valiant attempts but no one got it.

The clue was my mention of iridium lifetime plugs. I could have put "lifetime" in quotes but I thought that would make it too easy.

I found the solution when I watched an EAA webinar on RV maintenance by Vic Syracuse, during which he mentioned hard starting as a symptom of the internal resistors breaking down in plugs that otherwise look fine. I never knew to check that so I did so and all of them were way over the recommended max of 5000 ohms, and at least one was infinite. It turns out these "lifetime" plugs (for which I paid nearly $100 ea. 12 or so years ago), have this problem where the resistors break down regardless of their "lifetime" claim (and cost). Vic mentions this in at least two EAA RV webinars and Mike Busch has talked about it in engine webinars and articles as well.
https://eaa.org/Videos/Webinars/Aircraft-Building/6115329634001
https://blog.aopa.org/aopa/2015/03/19/champion-from-denial-to-acceptance/

Champion claims to have fixed the problem but I'm done paying that much for spark plugs that may or may not last, so I replaced the "lifetime" plugs with the regular kind (from Unison). I've also since switched the P-Mag harness to an automotive plug harness (which is all that they offer now anyway) and am using throwaway automotive plugs with that.

As for the starter fluid, I would guess that helped because there was still some spark, just not enough for starting without that extra "oomph". Plus it turned out to be a nice obfuscation in the tradition of click and clack!

To me a side message is, go watch the EAA's RV maintenance webinars by Vic Syracuse AND similar webinars about engines by Mike Busch. Fantastic resources that hit many of the highlights of what we typically run into in RV maintenance-land.
 
These will have been the old Champion plugs. If you look in the hole where the plug lead goes, the old design have a screw driver slot in the base. New ones, or Tempest do not.

That high resistance is hard on the coils of mags too apparently.
 
Good one Randall! I used to listen to Click and Clack every Saturday morning and loved the puzzlers and especially the "write your answer on a (whatever) and send it...

Thanks for sharing.
 
Well Done

Tommie and Ray Magliozzi would be proud of you.

Now all you need is advice from Dewey, Cheatham, and Howe.
 
Tempest Plugs

Every annual I check the resistance of my plugs. Never let them go over 2000 ohms.
BTW... I have had one in ten new Tempest plugs (after maybe 50 hrs ) show "open". I think they have fixed the problem though. They will replace "open" plugs unless they were purchased in 1975. John
 
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