Engine Starting Issue, O-360

[Chris from PA]

Here's what I'm dealing with lately (last 6 months) in my '65 C:

First start of the day is no problem.  Go through the start procedures, turn the key to "start" and within a couple of prop swings the motor fires right up.  Next, I fly a couple of hours, land and refuel, grab a snack, etc and I'm back in the plane within 20 minutes and ready to go.  Once again, go through the start procedures, turn the key to "start", and the prop swings but the engine doesn't even sputter or cough.  However, as soon as I realease the key to "both" the engine roars to life.  Same procedures, different results with the only variable being a cold engine vs a warm engine.  We've checked the timing and cleaned/adjusted the points on the left (Bendix) mag.  Thoughts? 

[bradp]

(Insert Anthony disclaimer here) 

What kind of starter do you have? Impulse coupled, retard breaker or SOS? Hot starts will always be a bit tricker but should be not so much of an issue for a carbureted O-360. Reason I ask about the type of starter  is that if it's a light weight high speed starter you might be getting enough prop RPM during a hot start to retract the pawls on your impulse coupling if that's what you've got ... which means your timing would be too advanced for starting... until you release the starter circuit on the ignition.  Then the prop slows and you catch.  

Are you getting a solid and distinctive "clunk" when you turn the prop through by hand? 

Other think to think about would be an issue with grounding of the Mag.  However that the engine catches when you release suggests otherwise.  

Only need four things to start: 

air, fuel, compression and spark (and spark timing as a separate concept).  Rule out compression, air and fuel and then you're left with spark.  

 

[smwash02]

You'll need to check the schematics, but this can mean the left mag isn't working right. In the start position only the left mag is activated and when you let it slide to both the right picks up the slack.

I had the same problem, only happened when hot.

Edited November 14, 2016 by smwash02

[Raptor05121]

14 minutes ago, bradp said:

 

What kind of starter do you have? Impulse coupled, retard breaker or SOS?

 

 

 

don't mean to hijack, but can you elaborate on the retard breaker versus shower of sparks? Mine is an A1D with a vibrator, am i correct in assuming SoS?

[smwash02]

Just now, Raptor05121 said:

don't mean to hijack, but can you elaborate on the retard breaker versus shower of sparks? Mine is an A1D with a vibrator, am i correct in assuming SoS?

Retard breakers are mags that have a second set of points to generate a spark at a retarded ignition timing.

We have SoS.

[Chris from PA]

Interesting thought on the starter.  I've got a Sky-Tec lightweight starter (model 149-NL) that's been on the plane for 5 years.  If this is my problem, what's the solution?

I was leaning towards a grounding problem, or an issue with the ignition switch, but since the problem doesn't appear when the engine is cold I'm still scratching my head.  

[neilpilot]

2 hours ago, Chris from PA said:

Here's what I'm dealing with lately (last 6 months) in my '65 C:

First start of the day is no problem.  Go through the start procedures, turn the key to "start" and within a couple of prop swings the motor fires right up.  Next, I fly a couple of hours, land and refuel, grab a snack, etc and I'm back in the plane within 20 minutes and ready to go.  Once again, go through the start procedures, turn the key to "start", and the prop swings but the engine doesn't even sputter or cough.  However, as soon as I realease the key to "both" the engine roars to life.  Same procedures, different results with the only variable being a cold engine vs a warm engine.  We've checked the timing and cleaned/adjusted the points on the left (Bendix) mag.  Thoughts? 

 

48 minutes ago, Chris from PA said:

Interesting thought on the starter.  I've got a Sky-Tec lightweight starter (model 149-NL) that's been on the plane for 5 years.  If this is my problem, what's the solution?

I was leaning towards a grounding problem, or an issue with the ignition switch, but since the problem doesn't appear when the engine is cold I'm still scratching my head.  

If the starter turns when the engine is hot, and "as soon as I realease the key to "both" the engine roars to life", how could the starter be the problem.

[par]

When I was new to my C, I also had got starting issues. They were much like yours and almost exactly the same. Over time I learned that with a hot start, I have to pump the throttle a couple times with the engine turning and it will generally fire right up when I do so. Also, just like your C, cold starting is not an issue at all except on the exceptionally cold mornings. If you haven't tried this method, I would recommend it at least a few times before you open up your wallet for a problem that may not exist.

[DXB]

2 hours ago, Raptor05121 said:

don't mean to hijack, but can you elaborate on the retard breaker versus shower of sparks? Mine is an A1D with a vibrator, am i correct in assuming SoS?

 

2 hours ago, smwash02 said:

Retard breakers are mags that have a second set of points to generate a spark at a retarded ignition timing.

We have SoS.

My understanding was that there is no difference - i.e. the SoS system is comprised of a starting vibrator that fires a set of retard breaker points in the left mag only that delay spark until TDC. Of note, Don Maxwell's article on the system states that the engine not firing until the key is released to "both" can indicate a failing SoS system - I assume because you might not be getting adequate spark via the retard breaker points?  Here's the link to the article:

http://www.donmaxwell.com/publications/MAPA_TEXT/Shower of Sparks/Shower of Sparks.htm

BTW I've had intermittent trouble with hot starts in my C, but I assume this is related to flooding as the flooded start procedure with the throttle full in seems to work.  

[Johnnybgoode]

I think it's D Maxwell that has a hot start technique video on YouTube - I have found it to be quite reliable on hot starts. Don't know if it will fix your specific problem (yours sounds like a mag problem to me) but generally it's an effective "hot start" starting point procedure for our old carb'd birds.

good luck,

Patrick

[mccdeuce]

I may be selling my used electro air e-mag that I bought to put into the M20E I was buying but didn't. 

I have been told that they greatly ease the start.

[bradp]

Fully agree Neil, the starters job is literally to turn the engine, it does NOTHING else.   

It's not the starters fault. I promise. It is uncovering a problem with hot starts because the engine is not turning over and the starter continues to do its job working round and round - for impulse coupled mags this continued turning will go faster and faster. Eventually it is fast enough to make the impulse couple move from "start mode" to "run mode" and the timing changes to one which is darned difficult to start an engine with.

So any cause of poor hot starts can result in the starter working the engine faster around. The weird part to the OP story is that it consistently catches when releasing the ignition start.

If impulse coupled I'd think weak spark, bad impulse coupling, etc. If SOS, weak battery, etc might result in similar behavior.

Sorry above I said retard breaker or SOS. I should have said SOS or slick start. SOS is a type of retard breaker. Slick start is solid state and can be used with either retard breaker mag or impulse coupled mags. We could probably draw a nifty Venn diagram. :-)

... that's why I asked about whether he is impulse coupled.

See what the experts think.


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[Guest]

During the start sequence, the right mag P lead wire is grounded at the switch, it remains grounded until the switch is released to the both position.

If the engine only starts when the switch is released, the trouble is in the left magneto, the SoS system or the impulse coupling.

All magneto manuals, including SoS are available on the Continental website.

Clarence

[Chris from PA]

Thanks for all the input.  I'll take your suggestions to my mechanic and we'll come up with a plan to work our way through the troubleshooting.  

[Hank]

My C reached the point that it cranked every time when I let go of the key. When it would crank . . . Infrequent firing while turning over. Drove me and my A&P crazy! He thought the carb was the problem, since I couldn't force flood it and make fuel drip out of the cowl. This worked for a while, then back to hard starts. Went through the SoS, and it's been great for several years until one of the mags had to be IRANed. That started out with occasional 200-250 RPM drops at runup and progressed rapidly to rough running and spitting while taxiing away from the hangar, so I put her back in and called for help.

Good luck with yours! At this point, check the SoS.

[tony]

you really need to answer Raptor05121's question.  Do you have a SOS?  Has SI 1325A been done? What are you timing the engine to? 25 or 20 degrees?  we really need all this information to figure out whats going on.  

 

[ShermAv8tor]

I had the exact same issue, turned out to be the wiring between the start switch and the mags, it was grounding itself out on the shield to core in the p-leads - I decided to run all new wiring and install all new p-leads - problem solved. I was able to find it by ohming out the wires and when I wiggled the wiring around it showed up. Good luck, electrical problems can be time consuming chasing something else…like the carb. If it's the bendix ignition switch, there is a SB that you can use to ohm & check that as well with an ohm meter.


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[orionflt]

sounds like a problem on the retard portion of the mag/SOS system there is also a second set of points on the left mag just for the retard portion of start. if you want to bring it over to Quakertown some weekend we can troubleshoot it.

Brian