Starter Issue

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Dan Gordon

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Installed new twist to start ignition switch 3 months ago - Piper Cherokee 140. Yesterday plane started easily, I shutdown, filled fuel. Upon restarting, turn key and all I got was a click, click, click from under the cowling. Let sit 20 mins — same thing. Voltage indicated was 12v. New battery installed 6 months ago.

Any ideas? Hopefully my mechanic gets to it this week as it’s perfect flying weather up here in New England.
 
Have battery load tested. Check amp draw on starter, when was it last serviced.
 
Its last “major” service is when the twist to start ignition and a Surefly magneto was installed around 3 months ago. Had oil change and a dynamic prop balance in the last few weeks. Plane had no issues starting through the winter at all.
 
Dan Gordon said:
Upon restarting, turn key and all I got was a click, click, click from under the cowling
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That says that the contactor's plunger is moving, but the lack of action implies either worn-out contacts in the contactor, or the starter has a bad spot on its commutator.

Weak battery or dirty or loose cables will usually make the starter weak, not suddenly completely dead.
 
The first stop is to check the battery. If the open circuit voltage is 12.0V, the battery is 60% discharged. A fully charged battery should have an OCV around 12.6-12.8 V. In addition, the battery may not have sufficient load capacity despite having 12.0V available. Under load, the battery may not be able to maintain enough voltage to keep the solenoid engaged when the starter draws power.
 
I will check the battery. Maybe it had enough juice to start the plane one time and that is it.
 
Dan Gordon said:
I will check the battery. Maybe it had enough juice to start the plane one time and that is it.
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If it was a really weak battery, the contactor would chatter. That's caused by the starter's low resistance causing enough of a voltage drop that the contactor falls open, disconnecting the starter and letting the voltage rise again, and then the contactor closes again. Over and over, at maybe 40 Hz.

I still think the contactor or starter is bad.
 
Could also be a gunked up starter bendix. Very common with the OEM starters. Proper remedy is to pull the starter and clean the gunk or replace the bendix. Common remedy is to spray the crap out of the bendix with brake cleaner to soften, liquefy, and drip out the gunk. Let the brake cleaner evaporate before starting.
 
Domenick said:
Could also be a gunked up starter bendix. Very common with the OEM starters. Proper remedy is to pull the starter and clean the gunk or replace the bendix. Common remedy is to spray the crap out of the bendix with brake cleaner to soften, liquefy, and drip out the gunk. Let the brake cleaner evaporate before starting.
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The pilot can hear the starter spin if the Bendix is stuck. All the OP heard was a click.

The only effective way to clean that Bendix is to take the starter apart. Been there, done that several times.

Mechanics or owners using oil of any sort on the drive are the problem. Only dry silicone spray is to be used. Oil attracts dust and reacts with water to form that gunk.
 
Domenick said:
Could also be a gunked up starter bendix. Very common with the OEM starters. Proper remedy is to pull the starter and clean the gunk or replace the bendix. Common remedy is to spray the crap out of the bendix with brake cleaner to soften, liquefy, and drip out the gunk. Let the brake cleaner evaporate before starting.
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The pilot can hear the starter spin if the Bendix is stuck. All the OP heard was a click.

The only effective way to clean that Bendix is to take the starter apart. Been there, done that several times.

Mechanics or owners using oil of any sort on the drive are the problem. Only dry silicone spray is to be used. Oil attracts dust and reacts with water to form that gunk.
074_4.jpg
 
Did the OP only hear "click, click, click?" I know that is what was reported, but sometimes reporting is incomplete.
I've had one bout of "click, whir." Spraying the crap out of the bendix with brake cleaner did provide a temporary fix. So did bumping the starter just after shutdown when the bendix gunk was warm. This threw the bendix gear into the ring gear ready for the next start. Shortly after, I did the proper repair, pulling the starter and replacing the bendix and the starter brushes. I considered just soaking the bendix drive in solvent for a few days, but at the time replacement bendix drives were only about $70.
 
My battery was low on water, it’s been filled and put on a trickle charger. The bolts are reading low. My mechanic will test another battery with the system, test the starter and the connector. See what happens from there. My current battery after charging still got only a repeated click, click, click from the system. The voltmeter in the panel is reading higher than the actual voltage from the battery.
 
Dan Gordon said:
The voltmeter in the panel is reading higher than the actual voltage from the battery.
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Checking and adjusting system voltages in an airplane is ideally done with a calibrated meter. A cheap meter from Harbor Freight isn't going to cut it.
 
My mechanic is going to pull the starter and bench test it…
 
Dan Gordon said:
My mechanic is going to pull the starter and bench test it…
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Before he does that he should take voltage drop measurements across the starter contactor. Takes a few minutes but could save a lot of time if it's the contactor at fault.
 
I think you can use jumper cables to jump across the solenoid contacts. If the prop turns when the starter is engaged, then likely the solenoid.

Any one see any potential gotchas with this in-place test?
 
Starter was benched tested and is good. Going to clean the original cables coming off the battery and or replace them with copper cables. We aren’t getting full voltage from battery to starter as I understand it.
 
Dan Gordon said:
Starter was benched tested and is good. Going to clean the original cables coming off the battery and or replace them with copper cables. We aren’t getting full voltage from battery to starter as I understand it.
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Has the battery been shown to hold a full charge (12.6-12.8V)? And can it pass a load test? If the battery is sulfated from being low on electrolyte, it may not be able to deliver enough current under load to run the starter. My suspicion of the battery would increase if it is more than 5 years in service. If the battery can't hold 9V under starter load it's toast.
 
Dan Gordon said:
Battery is only 5 months old. It holds a charge.
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Chemgeek also asked about a load test on the battery. Have you done that? A battery that is sulfated or has high internal resistance for one or more other reasons can take and hold an apparent charge, and display a normal static voltage, but under a high current load its voltage drops sharply. It will produce the symptoms you are experiencing.

You mentioned that your mechanic was going to test the system with another (presumably known good) battery. What was the result of that test?
 
Yes sir. That’s next on the docket. 3 batteries were tested with no luck. Unless there is an electrical gremlin, it should be the solenoid. All other panel mount electronics work.
 
So much time and money wasted fooling with batteries and starters, when a few minutes doing simple voltage drop tests would reveal the culprit instantly. This messing around for days is way too typical, and it's the result of not understanding the systems.

1714326372596.png

Go to https://skytec.aero/aircraft-starter-performance-issues/ for details. Stop messing with stuff and do this instead.
 
Yes sir. That’s next on the docket. 3 batteries were tested with no luck. Unless there is an electrical gremlin, it should be the solenoid. All other panel mount electronics work.
 
Dan Thomas said:
So much time and money wasted fooling with batteries and starters, when a few minutes doing simple voltage drop tests would reveal the culprit instantly. This messing around for days is way too typical, and it's the result of not understanding the systems.

View attachment 128244

Go to https://skytec.aero/aircraft-starter-performance-issues/ for details. Stop messing with stuff and do this instead.
Click to expand...
Yep. No reason to remove parts before working down the chain with a voltmeter, upstream to downstream, starting at the battery.
 
chemgeek said:
Yep. No reason to remove parts before working down the chain with a voltmeter, upstream to downstream, starting at the battery.
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NO. Do it in the order shown. Saves time. Read the details in the website.

Voltage DROP measurements are what we use to find the tiny resistances that cause starter problems. As little as 1/20th of an ohm can cause a huge drop at the starter. Most ohmmeters will never spot that. For the starter contactor put the positive voltmeter probe on the battery side of the starter contactor (big terminal) and the negative on the starter side (other big terminal). Turn the master on, and you will see battery voltage. Crank the engine, and the voltage should drop to zero. That's because the contactor takes all the current and none goes through the meter. If you see anything more than half a volt there during cranking, that contactor is worn. In the OP's case, I'd bet that the drop there is on the order of eight volts or more. That starter isn't going to wake up on the remaining four volts.
 
Dan Thomas said:
Checking and adjusting system voltages in an airplane is ideally done with a calibrated meter. A cheap meter from Harbor Freight isn't going to cut it.
Click to expand...
The cheapest Harbor Freight digital meter is about as good for accuracy as the AVOmeter/Simpson 260/Triplett 630 analog VOMs commonly used back in the day.
 
Dan Thomas said:
So much time and money wasted fooling with batteries and starters, when a few minutes doing simple voltage drop tests would reveal the culprit instantly. This messing around for days is way too typical, and it's the result of not understanding the systems.

View attachment 128244

Go to https://skytec.aero/aircraft-starter-performance-issues/ for details. Stop messing with stuff and do this instead.
Click to expand...
It will take me days to read this image and understand it. Haha
 
flyingbrit said:
The cheapest Harbor Freight digital meter is about as good for accuracy as the AVOmeter/Simpson 260/Triplett 630 analog VOMs commonly used back in the day.
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By "calibrated" I mean tested and certified to a national standard. Even those old analog meters varied somewhat. When you're setting the voltage regulator, accuracy matters, a lot. This is a typical setting chart from the Cessna alternator and regulator maintenance manual:

1714411201614.png
So, basically a tolerance of +/- 0.2 volts. Batteries are fussy about charging voltage; too low, and they sulfate. Too high, and they lose the electrolyte too quickly. Either of those will shorten battery life. I would not set a regulator using any of my many uncalibrated multimeters.
 
mandm said:
It will take me days to read this image and understand it. Haha
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Which is why so many mechanics don't do it. They somehow got through their training without any real grasp of electrical principles. That's sad, considering that electrical problems are the biggest single source of aircraft problems.

Imagine a doctor who diagnoses your complaint by cutting you open repeatedly and removing or transplanting various organs until the problem goes away. With all the non-invasive diagnostic tools at his disposal, you wouldn't think much of his "troubleshooting," would you?
 
Here's the older PDF version of the Skytec troubleshooting guide that was replaced by the Skytec webpage that Dan linked to above. Handy to print out and keep at the hangar.
 

Attachments

  • Starting System Troubleshooting Diagram_5.0.pdf
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A&P didn’t have to replace anything. Went through the system starting at the battery and working forward, cleaning all connectors, contactors, etc. Without going into too much detail, once this was done plane started right up.
 
Thanks for the update. Any details that your mechanic found that you think was the main problem? Might help the rest of us someday. TIA
 
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