Intermittent Starting Problem

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CamG

Filing Flight Plan
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CamG
I have had an intermittent start issue pop up every now and then. It has probably happened 15-18 different times during the first year of ownership of my 1976 Piper Archer II. Every time I try to have my A&P check it out I can never replicate the problem. Excuse my ignorance on airplane mechanics as I am a very green pilot and airplane owner with less than 200 hours.

This intermittent start problem usually occurs only after flying for a period of time, stopping the plane, and then trying to re-start. Only once or possibly twice has it occurred on a cold start situation. After re-fueling or whatever the case may be and attempting to re-start the plane I will only get a "click" noise when attempting to turn the key to the start position and that is all that happens. I can see the volt meter drop when I move key to the start position, but all I get is the click. The clicking noise is my starter solenoid as I have had someone attempt to start the plane with the cowl off and you can feel/hear the starter solenoid make that click noise, but the starter does not engage and the bendix does not engage the flywheel. The only thing that seems to solve the problem is time, I have had cases where it started back up after various attempts in 5, 10, 20 minutes and all the way up to 3-4 hours after trying to re-start after a multi-hour flight.

I am stumped as to what it can be and why it randomly starts working again and the starter engages after an arbitrary amount of time with no work done to the engine. A few times I have taken a wrench and actually turned the teeth of the bendix with it not engaged just to see if the metal had expanded during the heat of flight and it seemed to help? But maybe it was just a coincidence that after I turned the bendix teeth a few times it was just the right amount of time waited and the starter engaged. So I started by replacing the starter solenoid with a brand new unit back in January which did not fix the problem and the current starter in the Archer is a Lightweight Sky-tec 149-12 XLT which was installed brand new on the engine at overhaul in the summer of 2016 and the engine has a little over 300 SMOH currently.

This intermittent start issue is driving me nuts, it happens at the most inconvenient times and has caused me to sleep on a dirty FBO Pilots Lounge couch in the middle of nowhere Louisiana (Da Quincy) before. It is so hard to replicate as it doesn't happen every time so I have never had an A&P be there when it happens to troubleshoot the issue. I have had A&Ps tell me it could be a grounding issue or perhaps I need a better starter. Are there any suggestions from the awesome pilots in this forum? I am open to all suggestions and will be happy to describe further or clarify anything if anyone has any questions. Thanks!
 
It wasn't an airplane, but I had a motorcycle with similar problems a few years back. It tuned out to be the battery, which was only a year old. When I was riding the motorcycle it was charging the battery properly, not over charging it, but the faulty battery was still getting hot enough to expand inside just a bit, causing it to short out and lose a cell. When it would cool down it would return to working normally. Once the battery was swapped out for a new one, end of the problem.
Not saying its your battery, just pointing out the possibility is all.
 
I wonder if you might have a dead spot in the armature. Not sure how to test for that other than swap out the starter.
 
That's why it's good to know how to hand prop. :p

You say you see a voltage drop when you turn the key, how much drop and what is it before? How does that compare to the voltage drop during normal starting?

It sounds like a bad solenoid but you already replaced that, so it has to be something else. A bad connection at the battery would be the next thing to look at. It could be a grounding issue, either at the battery or engine. If it's not that then it's probably something internal to the starter motor, brushes and commutator ring the next place to look.
 
The starting circuit is rather simple. A battery, a switch, a solenoid, and a motor with a bendix and connections. Start Eliminating things.
 
Sounds like a break in one of the starter windings to me, when the starter is hot the coil opens up (no continuity).
 
Start with easy/cheap first. Are the connections between the battery and starter clean? BTW the easiest way to tell is to disconnect and clean them and re-tighten them. Make sure to check grounds as well.
 
Greg Bockelman said:
I wonder if you might have a dead spot in the armature. Not sure how to test for that other than swap out the starter.
Click to expand...

A current probe and oscilloscope would test for this quite well. Finding a mechanic with this equipment might be a challenge though.
 
The starter might have a dead spot, but there's also the possibility that the master solenoid is shot. All the starter current travels through the master and starter solenoids, and if either one of them has much resistance in its contacts, it won't carry the significant current to drive the starter. If the master is bad, anything else that's on while you crank will get dim. Turn on the panel lights or something and try cranking. If they dim very badly, that master is shot.

Skytec has a solenoid as part of the starter, too, and it might be defective.

As others have said, check the connections. It only takes a bit of looseness to cause trouble. Check the engine ground strap, too.
 
Thanks for all the input. Yes I might try replacing the master solenoid next. I have also been told by another A&P that they starter I have is a little too lightweight for my plane and he recommended getting the next size up in the Sky-tec line. I just got a brand new Concorde battery put on during annual in November so the battery is brand new. This problem existed before my annual on the old battery and continued since the annual on the new battery.

The voltage when I click the master on usually hovers around 12.4-12.7 and then when the starting problem is happening and I turn the key to the start position and all I hear is the click the voltage meter drops down to about 11..2-11.3 if I remember correctly and then back to 12.4-12.7 when I stop holding the key in the start position. Isn't that voltage drop normal?
 
The frustrating thing is it only happens intermittently and most of the time it starts up just fine with no issues. Just trying to figure out what causes the arbitrary issue. I really appreciate all the input.
 
Check your main ground and other contacts as others have suggested. I had similar issue but tended to not have any correlation to having been ran recently. I cleaned the main ground up and not a single issue since. There was black grime between the contact points, cleaned it and put some corrosion x on it. Free fix.

May not be it but sure is worth a try before throwing AMUs at it...
 
CamG said:
Thanks for all the input. Yes I might try replacing the master solenoid next. I have also been told by another A&P that they starter I have is a little too lightweight for my plane and he recommended getting the next size up in the Sky-tec line. I just got a brand new Concorde battery put on during annual in November so the battery is brand new. This problem existed before my annual on the old battery and continued since the annual on the new battery.

The voltage when I click the master on usually hovers around 12.4-12.7 and then when the starting problem is happening and I turn the key to the start position and all I hear is the click the voltage meter drops down to about 11..2-11.3 if I remember correctly and then back to 12.4-12.7 when I stop holding the key in the start position. Isn't that voltage drop normal?
Click to expand...

It shows that something more than the starter solenoid is drawing current. Might be the solenoid on the starter itself. If the starter windings were drawing, the voltage could drop to 8 or 9 volts, which suggests that the starter has problems or the engine is not well-grounded. You might put a voltmeter between the engine crankcase and the firewall, and see what it reads when you crank. Anything more than maybe a quarter of a volt indicates poor grounding.

You could also measure the voltage right at the starter cable lug and see what you get. If it's the same as battery voltage when you crank, and the starter doesn't run, you have a defunct starter.
 
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