Engine stops during the cranking

blueskyMD

blueskyMD

Pre-takeoff checklist
Joined
Mar 26, 2015
Messages
352
Location
Allentown PA
Display Name
Display name:
Bigfoot297
It happened twice now. On long cross country trips after refueling stop ( about 5-10 minutes ) I start to crank. Props spin enthusiastically and when I feel like it is about to start props stop spinning. I thought props hit some thing so got out and saw nothing. I rotated propellers through each cylinders and no problem. Got back on the seat and cranked again started without any trouble. Engine is IO 540 K1G5D Mag checks are good. Engine runs smooth . Starter was replaced about year ago with sky-tec. Battery seems to be good. Any idea whats going on?
 
It sounds like one cylinder (or more?) fired prematurely and the "kick back" stopped the rotation. This could be caused by:

1) Failed (or failing) ignition switch that isn't grounding the non-impulse mag during cranking. This is a known problem on certain Pipers, there is a SB out on it.
2) Failed impulse coupler in the one mag that has it installed
3) Carbon fouling in the cylinders. Bits of carbon glowing brightly and lighting off the fuel/air mix.

Try shutting down the engine with the key, not the red knob. If it continues to run even if poorly you have a load of carbon somewhere...

-Skip
 
Skip Miller said:
It sounds like one cylinder (or more?) fired prematurely and the "kick back" stopped the rotation. This could be caused by:

1) Failed (or failing) ignition switch that isn't grounding the non-impulse mag during cranking. This is a known problem on certain Pipers, there is a SB out on it.
2) Failed impulse coupler in the one mag that has it installed
3) Carbon fouling in the cylinders. Bits of carbon glowing brightly and lighting off the fuel/air mix.

Try shutting down the engine with the key, not the red knob. If it continues to run even if poorly you have a load of carbon somewhere...

-Skip
Click to expand...

Thanks Skip. I will ask mechanic to check on first two items. Carbon issues seems less likely since I always aggressively lean engine on the ground and in the air.
 
The Sky-tec starter is spinning the engine too fast. The impulse coupling, which has been retarding your spark, suddenly snaps back. Then you are at full "advanced" timing and your engine kicks back.

But, Sky-tec debunks this..............still seems to be common.

http://www.skytecair.com/Too_Fast.htm
 
How old is your battery? Is it charging to full capacity? That would be my first thought.
 
kgruber said:
The Sky-tec starter is spinning the engine too fast. The impulse coupling, which has been retarding your spark, suddenly snaps back. Then you are at full "advanced" timing and your engine kicks back.
Click to expand...

Yabut I have had the kick back on a PA-28 (Lyc O-360) with no Sky-tec installed.
 
Its not the ignition switch.

You have a D3000 series magneto, one drive that runs two dristributors, and my guess is that the impulse stop pin on the magneto or the spings on the impulse coupling flyweights are bad and its firing the spark plugs near 25 degrees BTDC instead of near zero degrees.

Or you have a weak battery, or high resistance in the starter circuit unable to flow enough power to the starter during peak demand, fresh oil in the cylinders would cause higher compression.
 
Last edited:
I had no problems with the SkyTec on my Cherokee...first guess would be the battery as well.

However, I defer to the experts :).
 
blueskyMD said:
Props spin enthusiastically and when I feel like it is about to start props stop spinning.
Click to expand...

If you are saying the prop stops while you have the key in the start position, it is the start system - anywhere from the battery to the master relay to the cables to the starter relay to the starter, the ignition switch, the ground. Unless the engine is seized, by something, temporarily, which I doubt.

Unless I misunderstand what is being said, I don't see how the engine can stop turning as described while the ig switch is in the start position because of a mag or spark plug problem.
 
Does it stop while the starter is still engaged? Does the engine fire at any point before it stops?
 
Lets go flying and dmspilot you both are correct.
The propellers stops turning with starter in the engaged position.
I am thinking along the line of starter issue.
 
My first thought was the ignition switch. Gotta keep it pushed in on the Pipers.
 
And as I mentioned earlier I did hand turned propellers through each cylinders so I doubt there is any inside engine related issue
 
Timbeck2 said:
My first thought was the ignition switch. Gotta keep it pushed in on the Pipers.
Click to expand...
I tried to start the engine the same way I have done it hundreds of time.
I guess I need new starter since it has close to 2000 hours on it.
 
Timbeck2 said:
Well in my defense and only going by the picture in his avatar, I can't tell the model year of his airplane. :dunno:
Click to expand...
Defense not necessary. I've never flown with a "push me" switch, so if in fact his plane were that old, I'd have missed it completely. Each post adds a bit of information. -Skip
 
Skytechs need lots of power hence the free troubleshooting guide to identify issues in the starter electrical circuit. A small resistance from a corroded terminal on a solenoid can really limit amperage going through it. Since that easy for any gearhead to troubleshoot I'd start there but I still suspect the lone magneto drive's impulse coupling. A quick logbook check should help shed some light on its age and history. Check battery age at the same time. If its not a sealed battery time to check electrolyte level.

http://www.skytecair.com/Troubleshooting.htm
 
bnt83 said:
Skytechs need lots of power hence the free troubleshooting guide to identify issues in the starter electrical circuit. A small resistance from a corroded terminal on a solenoid can really limit amperage going through it. Since that easy for any gearhead to troubleshoot I'd start there but I still suspect the lone magneto drive's impulse coupling. A quick logbook check should help shed some light on its age and history. Check battery age at the same time. If its not a sealed battery time to check electrolyte level.

http://www.skytecair.com/Troubleshooting.htm
Click to expand...
Thanks bnt83
Solenoid is about 2 years old ( I used to go through a new solenoid once a year and it turned out that starter was the one destroying the solenoids hence new starter) I will still check terminals.
Battery is Concord sealed one but is 5 years old. I do not remember it being load tested ( unless mechs did it during the annual and not told me ) But I fly regularly with at least 2 long XC a month so I always thought battery is in good shape. It does crank props at pretty high speed.
magnetos rebuilt last annual in October as per AD requirement
 
Last edited:
Load test the battery..... or spend a lot of money then check the battery.
 
I'd look at the solenoid or relay (depending on the plane) between the battery and starter. Corrosion, bad spot, wiring, etc. can all lead to this. Likewise a starter switch in the plane that's getting flaky. I'd check there first, but also ask does this only happen when the engine is hot/warm? If so, some of the thoughts on the impulse system may be to point.
 
Start simple, load test battery, if its good, look at cables, connections, and solenoid. Then look at more expensive stuff.

My guess: Hot start the rings and cylinder are well oiled, so you're getting max compression. Starter isn't getting enough current to overcome the compression.
 
On my 74 Beech you need to push in and turn the ignition switch. Sometimes on start I relax and don't keep the switch pushed in, disconnects starter.
 
PaulS said:
Load test the battery..... or spend a lot of money then check the battery.
Click to expand...
I thought load testing is capacity testing and does not say anything about cranking power. Your battery can spin the propellers like a champ but still fail load test.
 
blueskyMD said:
I thought load testing is capacity testing and does not say anything about cranking power. Your battery can spin the propellers like a champ but still fail load test.
Click to expand...

Load testing checks the battery's ability to power the starter. If the battery is weak it will not provide enough current to power the starter through compression strokes. The load test checks the battery voltage drop at high amperage load for a period of time, like 15 seconds. It will quickly tell you if the battery is up to the task. If the battery checks out, then, as mentioned by others, check for terminal corrosion from the battery to the starter. Eliminate the simple stuff first. In fact, I would start with the battery terminals and other terminals, make sure there is no corrosion and they are tight. Start simple before you start chasing magnetos and other things unless something else specifically points you in that direction.
 
If you say it spins "enthusiastically" then stops dead I would say the second post pretty much covers it although I don't think glowing carbon would last that long.
I have had this happen on my Grumman tiger when I started on the wrong mag, it has a push button starter so you can select either or both mags.
 
Hot engine, higher compression.

How about those battery cables? Aluminum or copper? If aluminum you need to get Bogert copper cables.
 
You must log in or register to reply here.
Back
Top