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Intermittent Start

bjdecker

Well Known Member
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First off, I despise intermittent problems -- they're challenging to reproduce, and by their nature, often lend themselves to false hypotheses, rabbit holes, etc.

So..that being said -- here we go.

My (nearly) new RV-7, with Lyc. IO-360-A1B6, has developed an intermittent starting issue when Hot (clue?). Turning the key to "Start" and I am rewarded with a >CLUNK< sound from the nose of the aircraft. Volts are 13.2Vdc (I have a LiFePo battery) and there's no indication of anything happening. Shoot -- release the key, gather my thoughts, shimmy in the seat a bit, check everything, try again - turn the key to "Start" and Wha-Vrooom...she starts on the first blade -- what the ????.

As mentioned, I have an Earthx ETX680. The buss volts are 13.2Vdc and there's no visible sag during cranking as displayed on the Garmin G3X.

So, could it be the Van's starter relay (ES-24021) not engaging good enough? The Skytech 149LS-12 motor or starter drive solenoid? Or....? Worth mentioning, I originally did NOT have a wire running from the "I" terminal to the starter motor solenoid -- However, I added the wire, removed the jumper per RV-10, RV-14 plans...issue still happens.

Any brilliant suggestions would be appreciated.

Brian
 
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Replace the starter with something better (B&C or NL),or the starter solenoid if you're on a budget.
 
If you want to troubleshoot try measuring the voltage drop across the start contractor. If it is anything but a volt or so, it is bad.
 
I had a similar problem. After a LOT of trouble shooting we discovered the ?clunk? was the starter gear teeth not meshing with the flywheel teeth. This was with a new starter. I discussed this with Skytec and was told the lightweight starter doesn?t have enough torque to turn when the gear teeth aren?t meshed with the flywheel teeth. I returned the Skytec and installed a B and C and have not had ANY problems since.
Bruce Estes
 
Check all ground paths.

Engine should have dedicated ground strap to airframe.

Look for any loose connections.
 
I had exactly the same issue.
Here's the response when I queried Hartzell Engine Tech about it:

"Given the serial number provided, I believe you have a part number 149-12LS starter that incorporates an external solenoid. From your description of the issue, it sounds as if the solenoid is not transferring the power across and into the motor. This is an issue we have found on this style starter we inherited from SkyTec and in fact, have an open review on this product resourcing a more robust solenoid.

There are no repairs approved for this model starter so if the problem persists, replacement would be the only option. You do appear to be eligible for warranty consideration given the installation date provided. Please complete the attached warranty form and return to me by email so I can provide an RMA number for return of the starter for evaluation."

They were great to work with. They sent me a replacement and it's been fine ever since.
Regards,

Tom
RV-7
IO-360M1B
 
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Apparently there are several failure modes with the same symptoms.

I had the exact same symptoms. I put wires to on the start solenoid power in, and on the starter solenoid activation post to measure voltage and found that it was the (Vans sourced) start solenoid that was failing. Specifically, the start solenoid would click, but no volts would register on the output post (I) that was intended to actuate the starter solenoid. The high amp post was getting voltage. I replaced the firewall solenoid (25hrs). The new solenoid worked flawless for 75 hrs. A PITA to install.

Last week it had a hiccup, only this one time did it click and not activate the starter. Turned key to start again . . . and it was fine. Not sure it is the same failure, but still have instrumentation wires available and will reconnect if the condition persists.

BTW-I took the part apart (drilled rivets) found a floating brass part apparently not making good contact. I bent the corners to ensure a connection and reassembled with #6 screws. All other contacts looked brand new, as expected.

EDIT - if the sound is really a clunk (starter gear engages, but not turning) and not clack the solenoids activating, then I am with Walt's solution.
 
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Hmmm...

All - thanks for the commentary, I have more work to do here.

Bill, when you say Solenoid do you mean the Starter Relay that's mounted on the firewall - black thing with 4 terminals, "S", "I", and two massive copper studs? Or the actual solenoid that's incorporated into the starter?

Tom - yeah, that's about the same email I got back from Hartzell, but they didn't indicate a problem with a certain batch of starters....yet - will chase this avenue also.

Mike - thanks, all good there - but always worth another look.

Walt - Seen B&C stuff - what's NL? Is that a brand or another style of starter?


Thanks,

B
 
intermittent start

Just wanted to add my experience to the intermittent starter issues.
Nearly new 149-12LS - when I push the start button - intermittently it would engage the solenoid, but not turn over the engine. After checking over all the connections and wire sizes, I reviewed the master solenoid specifications and found that there are differences in capacity and construction. I replaced the master solenoid with a higher capacity unit with silver contacts and my starter problem has gone away. It also turns the engine over noticeably faster. If anybody is having problems with their starter, they should review the condition/rating of their master solenoid.
 
Root Cause - Update

I removed the starter solenoid from the starter. The solenoid actuator/piston was heavily pitted and didn't move freely inside the sleeve -- It would partially retract when current was applied, but it didn't move far enough to complete the circuit to the starter motor.

I sourced a replacement from AutoZone (Borg Warner BWD S5613) and installed without any issues. New solenoid working fine.


Cheers!
 
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