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Starter On With Master. Safety Hazard.


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Just had a skytec installed 2 weeks ago. Today was going to be my second time out in the plane since the install. I’m curious if anyone has dealt with this before.

Started the engine and noticed my voltage hanging out at 10.8. Thought that was odd and noticed a sound from the engine that just wasn’t normal. So I sat there for a second looking things over and decided I better shut her down to investigate. I pulled mixture and to my surprise the prop never stopped. So I panicked. I killed mags. Nothing. Prop still going. Finally hit the master and everything came to a halt. Investigated up front and didn’t see anything out of the ordinary. Hopped back in the plane and sure enough, as soon as I flipped the master switch the starter engaged. 

It seems obvious to me that the ignition relay has failed/welded itself. Anyone else had that? It was pretty alarming. 

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Often...  when a starter stays engaged, it gets driven by the running engine... resulting in an over voltage...

In this case...  we lost sight of the detail regarding the 10.8v and why that is...

Following the description...   the starter is engaged and on... turning the engine and prop...

which... takes a fair amount of energy out of the battery, thus indicating a low voltage....

Cutting the electricity... takes power away from the starter...

 

If that is mostly true...

Something has caused power to continue to flow to the starter...

Starters get their power from their relay...

So... either the ignition switch is stuck on, delivering power to the relay...

Or the starter’s relay is stuck in the on position...

You probably... tried several positions of the switch... from off to on to start again...?

Double check the start position on the ignition switch... is it working normally?
 

Sounds like a good idea to check the starter relay to see why it is stuck closed...

Is it original, installed in the 60s?

How many hours does it have on it?

If you tap it with a rubber mallet, does it reset?

Back in the day, these things used to get OH’d... today they probably just get swapped out...

 

Take it over to your MSC...

You might need a new starter relay... they are overpriced... cost a ton... last about 50 years...  

 

On the other hand... If you already went to Jim’s MSC... somebody has accidentally swapped out your standard engine with one of those new fangled electric hybrid models without telling you...  you will need a much bigger battery pack to go with that...

:)

The good news... if you look around here... Skytec has a troubleshooting guide... that is probably worth a read...

Imagine for a moment... a starter relay that has been connected in the same system for years.... always closing in the same place.... while driving the same tired starter....    Suddenly, a new starter enters the old system... with nicely cleaned contacts.... causing the relay to close to a slightly different position... slightly past the groove or step that has been worn in... over the years...  

If you were the old relay... would you protest, and stay hung up?   

PP thoughts only, not a mechanic...

Best regards,

-a-

 

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It's common enough that a lot of airplanes have a starter engaged light to alert of such a problem.  The cause is usually a starter relay whose contacts have welded themselves together.  Root cause is low voltage from cranking the engine quite a bit, running down the battery to the point of the relay beginning to drop out under load.  Big arc as the contacts move apart under load.  Good you caught it right after start, the new starter may be okay.

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8 hours ago, ltdriser said:

I’m not sure the model of skytec, I should probably know that. The plane is a ‘63 M20C. 

Well you are lucky one way, all the suspect parts are readily accessible. In some of the later models the starter relay is buried so deep you have to disassemble half the instrument panel to get to them.  

Edited by N201MKTurbo
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5 hours ago, N201MKTurbo said:

Well you are lucky one way, all the suspect parts are readily accessible. In some of the later models the starter relay is buried so deep you have to disassemble half the instrument panel to get to them.  

Yeah, for sure.  On my ‘68, the left cheek cowl could come off and the starter relay is right there attached to the firewall.  Looks really easy to swap out too.

Are the same metal relays still available or do we have to find tractor parts?

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7 minutes ago, Ragsf15e said:

Yeah, for sure.  On my ‘68, the left cheek cowl could come off and the starter relay is right there attached to the firewall.  Looks really easy to swap out too.

Are the same metal relays still available or do we have to find tractor parts?

You can get them from Sky Tec.

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If you ran the engine even at idle speed you may have toasted your starter

Think of the RPMs you drove it to while the engine was running. If you went above idle its even worse,

Be very careful working on it with a stuck relay as the mags might also be hot if its the mag switch problem 

AND the prop can KILL!

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12 hours ago, RLCarter said:

Disconnect the heavy wire at the starter while screw’n with it, keeps the prop from smack’n ya

I’d add, slide the terminal boot over the removed cable end to prevent a short to the engine case should it touch.

Clarence

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  • 2 weeks later...

Update!

The saga continues. I sent the plane back to mx and they replaced the starter relay. When I got the plane back it no longer started. The mx team said it started fine at their hangar when it left. 
 

I went ahead and had the plane sent back and again they mentioned they had no problems starting it. So I’m at 2x back and forth with the mx hangar. 
 

So to recap, had the plane looked at because of no start. Starter installed. 
Took plane to mx after starter stuck engaged. Starter Relay replaced. Returned airplane after starter relay replacement because of no start. Plane has been returned and still no start. 

 

This is beginning to look like a job for the hangar fairies as I am losing confidence in the ability of my field mx team. Any thoughts? 

Edited by ltdriser
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4 hours ago, ltdriser said:

The odd sound it makes is when I’m pushing in on the key. 

When you say pushing on the key, you’re pushing IN firmly, right?  Not just to the right hand, “start” position?  It sounds like the SOS was firing.  Obviously it didn’t turn over, but the SOS was going.  Id probably give the mechanic one more try, but have him sit in the airplane with you while you start it (or it doesn’t work) so you are on the same page.

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Yeah, I mean as far as I know I’m pushing it in hard enough. I’ve never had this problem before, and have many hours in the plane. Maybe I ought to give it a little more oomph. 
 

The odd thing is. It seems like it is bumping the starter right as I let off of pushing in. If you watch the video closely you’ll see the prop move to the right just a touch just as I let out of the key. Additionally, you can zoom in on the voltmeter and see the volts jump up to ~20vdc right as I let out for a split second. 

Edited by ltdriser
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4 minutes ago, ltdriser said:

Yeah, I mean as far as I know I’m pushing it in hard enough. I’ve never had this problem before, and have many hours in the plane. Maybe I ought to give it a little more oomph. 
 

The odd thing is. It seems like it is bumping the starter right as I let off of pushing in. If you watch the video closely you’ll see the prop move to the right just a touch just as I let out of the key. Additionally, you can zoom in on the voltmeter and see the volts jump up to ~20vdc right as I let out for a split second. 

Maybe you just have a bad ignition switch.

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56 minutes ago, ltdriser said:

The odd thing is. It seems like it is bumping the starter right as I let off of pushing in. If you watch the video closely you’ll see the prop move to the right just a touch just as I let out of the key.

I also noticed the prop twitched when letting off the key push.  My old Bendix switch wouldn’t engage the starter if the key was turned all the way to the right and then pushed in.  I had to sometimes turn the key slightly back to the left, while still pushed in, and then the contacts connected and the starter engaged.  

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Another update!

 

Went to the field. Turns out the starter does work woohoo! But she still won’t start. Boo!  I cannot engage the SOS and starter at same time. The starter will turn when I turn the key all the way to the right. As soon as I push in the key  for spark the starter stops. The two need to work together and it seems I can only get one or the other. 

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