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Engine Starter Stalling

T

todehnal

Well Known Member
I did a search on engine starter stalling, and came up with nothing. I must be the only guy with this condition. I keep a battery maintainer, designed for the Odyssey battery, on when not in use, but when I use the starter, it will stall at least a time, or two, before I get a spin up. Starting is always good, once I get a spin. It is important to note that this condition has been there since day one, and I now have 110 hrs. on it. I am beginning to wonder if I may have a weak battery? Today, I did a check. Without the battery maintainer hooked up, I checked the voltage after a few minutes of settling, and it was a 13.2 volts. With my meter still attached, I brought up the Skyview, and the voltage dropped to about 12.7. I then turned on the master, with all of the radios, auto pilot, and fuel pump on, and the voltage settled at 12.25. Then, when I shut everything down, the voltage came back, settling at about 12.8. That doesn't sound too bad to me, but I sure am no expert. I am considering adding an extra ground strap, directly from the starter to the battery, to see if it would help. Any thought will be greatly appreciated............Tom
 
What year is your Rotax and does it have the beefed-up starter? The newer model engines may come with the H-D starter but my last 912S from 1999 had the standard starter and it would stall and lag some. After I put the upgraded starter on it would crank good.
 
The engine was delivered form Van's in Dec. 2009. First flight was Nov 2013. Not sure if that would be a new style heavy duty starter, or not. MY reed switches are rock solid. I had lots of experience with reed switches in the computer industry in my former life, and I took all of the precautions during the build. But thanks for the thoughts. I guess it could be a bad starter, but the only way that I would know is to swap it out, and that would be expensive..........Tom
 
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Tom, did you check mounting and power connection? Starters are very fussy when ground or power conn. are even slightly off due to the voltage draw.
dick seiders 120093
 
Dick, actually, all I did was to tug on the leads, and they seem snug. I'm almost due for an oil change. I will remove, and reinstall the connection to the starter, solenoids, and battery, just to be certain. As an after thought, I guess it could be a bad internal contact on the start relay???


I see that Sky Tec makes an after market starter for the 912, touted as being lighter, with more torque, and faster spin for $400.
 
todehnal said:
I did a search on engine starter stalling, and came up with nothing. I must be the only guy with this condition. I keep a battery maintainer, designed for the Odyssey battery, on when not in use, but when I use the starter, it will stall at least a time, or two, before I get a spin up. Starting is always good, once I get a spin. It is important to note that this condition has been there since day one, and I now have 110 hrs. on it. I am beginning to wonder if I may have a weak battery? Today, I did a check. Without the battery maintainer hooked up, I checked the voltage after a few minutes of settling, and it was a 13.2 volts. With my meter still attached, I brought up the Skyview, and the voltage dropped to about 12.7. I then turned on the master, with all of the radios, auto pilot, and fuel pump on, and the voltage settled at 12.25. Then, when I shut everything down, the voltage came back, settling at about 12.8. That doesn't sound too bad to me, but I sure am no expert. I am considering adding an extra ground strap, directly from the starter to the battery, to see if it would help. Any thought will be greatly appreciated............Tom
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It would be interesting what the volts are when the starter is engaged. if memory serves me correctly the battery should maintain somewhere in the area of 9.5 volts. If it does then I would blame the stater? Larry
 
todehnal said:
Dick, actually, all I did was to tug on the leads, and they seem snug. I'm almost due for an oil change. I will remove, and reinstall the connection to the starter, solenoids, and battery, just to be certain. As an after thought, I guess it could be a bad internal contact on the start relay???


I see that Sky Tec makes an after market starter for the 912, touted as being lighter, with more torque, and faster spin for $400.
Click to expand...

I still have the original starter from my 912 and it's just sitting in my hangar collecting dust. Its yours if you want to give it a shot.
 
I am pretty sure all engines supplied by Van's were shipped well after the different starter began being installed.

One RV builder made a post a year or two ago about poor stater performance.
I don't remember specifics, but I think it ended up being an assembly error where the power cable attaches to the terminal stud on the starter, and the cable was slightly shoring to ground on the starter motor body.
 
I had a few, what I thought were starter/battery/electrical problems, during my first few hours. I never got the feeling that the Odyssey 6 amp charger did much to help (I no longer believe there is much value in leaving the charger plugged in all the time). What solved all of my issues was FLYING THE DARN THING! :D I try to fly my RV-12 2-3 times per week and everything works as it should. My hangar mate's occasionally-flown RV-4 has a 7-year-old PC-680 battery that has never seen a charger and it works fine after long periods of idleness.

ps -- I did add a second grounding cable from the battery to the firewall and a third grounding cable from the relocated (under the avionics tray) regulator to the engine. Not sure if that is necessary or helps, but at least I have strong grounding.
 
Remove the heavy cable from the starter and connect it to this Harbor Freight Battery Load Tester Ground the other lead of the Load Tester. While turning the start key, measure the voltage drop from the POSITIVE battery terminal and to the POSITIVE load tester terminal. If there is a significant voltage drop, measure at intermediate points to determine where the voltage drop is occurring.
Or just replace the master contactor and starter contactor and associated heavy wires. Doing that should cost less than replacing the starter and might solve the problem.
Joe
 
Think a minute about the rotation of an engine and what the compression reaction torque is vs crank angle.

When an engine rotates there is some aid to rotation on the cylinder coming up on compression from one that is expanding, whether it fired or not. Engines stop where the compression in the cylinders is balanced, then the pressure slowly leaks away. So, during a start the first revolution, and the first cylinder to come on compression is not fully filled with air, but the second one is. The compression pressure force of that cylinder is borne by the starter. If it passes tdc, then the torque of second cylinder to come on compression is aided by the first one expanding, thus the actual starter demand torque (amps) is less. Inertia also aids this process, an increases in its benefit as the rotation is accelerated.

Back to the first compression - being the greatest reaction torque and no benefit from inertia, this is all starter. So - if your engine has been doing this since new, then it is likely 1. increased resistance in the system sucking power from the battery, 2. a starter deficient torque capability.

Measuring the actual amps during engagement and first second of starting will tell the engine guys if your system is lacking or the starter is failing to turn the amps to torque.

Suggest you get the serial and part numbers of the engine and starter and enlist Vans people to research the situation to ensure you have the correct part and it is functioning to specification. The voltage drop test will validate your connections from battery to starter. Do both the ground and hot side.

Saving all that real data, a starter swap will do the same thing. Just be sure you test it under the same conditions of starting temperature of the engine oil.

Don't just do what is easy, do what is necessary.
 
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Infidel said:
I still have the original starter from my 912 and it's just sitting in my hangar collecting dust. Its yours if you want to give it a shot.
Click to expand...

Wow!! What an offer. Please let me do a bit more diagnosing. If everything continues to point to the starter itself, I may just take you up on your offer.

Thanks............Tom
 
LARCO said:
It would be interesting what the volts are when the starter is engaged. if memory serves me correctly the battery should maintain somewhere in the area of 9.5 volts. If it does then I would blame the stater? Larry
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Larry, I will make that test tomorrow and post the results............Tom
 
rvbuilder2002 said:
I am pretty sure all engines supplied by Van's were shipped well after the different starter began being installed.

One RV builder made a post a year or two ago about poor stater performance.
I don't remember specifics, but I think it ended up being an assembly error where the power cable attaches to the terminal stud on the starter, and the cable was slightly shoring to ground on the starter motor body.
Click to expand...

Thanks Scott. Another item that I will verify and post the findings. Thanks................Tom
 
DHeal said:
I had a few, what I thought were starter/battery/electrical problems, during my first few hours. I never got the feeling that the Odyssey 6 amp charger did much to help (I no longer believe there is much value in leaving the charger plugged in all the time). What solved all of my issues was FLYING THE DARN THING! :D I try to fly my RV-12 2-3 times per week and everything works as it should. My hangar mate's occasionally-flown RV-4 has a 7-year-old PC-680 battery that has never seen a charger and it works fine after long periods of idleness.

ps -- I did add a second grounding cable from the battery to the firewall and a third grounding cable from the relocated (under the avionics tray) regulator to the engine. Not sure if that is necessary or helps, but at least I have strong grounding.
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I have been in a wait and see phase for 110 hrs. now. We do fly often, usually several times a week. I flooded the engine once, trying a hot start, after a breakfast stop. I cranked that thing several times for extended periods before I finally got it cleared out, so that makes me think that the battery is just fine. These stalls seem to go away after the initial crank. I don't recall repeated stalls, during the engine clearing from my flooding booboo. Learned my lesson from that one for sure.
 
Compression lock?

I'm working on my standby generator for my house. Couldn't get the starter to turn over the engine no matter how good the battery. Turns out the valves had gotten out of adjustment and the intake valve pushrod had gotten bent. This was causing compression lock which the starter could not overcome. Not sure if the same thing is possible on the Rotax or if it would even run if one of the cylinders was having compression lock, but you could try pulling one sparkplug at a time and see if the starter turns the engine over (with the mags off). John
 
I really appreciate all of the thought that you guys have put into this. I do pull it through at least 4 blades before the first start of the day, and the compression seems very even, and normal. Bill offered some detailed tests to nail down the cause, and they will be on my todo list. It sounds like this may be a bit of a challenge to clear up, but I am determined to get to the bottom of it.

Thanks to all, and I will post the solution when it comes...........Tom
 
Is your Easy Start ignition module working correctly? Your engine should intially start at one RPM (say @ 1,650) and then automatically speed up to a slightly higher RPM (say @ 1,800) a few seconds after it starts as the timing automatically changes from starting mode to running mode. If your Easy Start is not working as designed, your initial incorrect timing may be hindering your start?
 
starter

One technique to try is the Buick racing V-6 starting process. Most of these engines had compression ratio's in the 15:1 range. To start these things you hit the starter with the ignition off and it would spin up quickly, then turn the ignition on. If you didn't do it this way it wouldn't turn over or it would break the starter off the block. Just another tool in the drawer. YMMV
 
PROBLEM SOLVED!!!

I finally had time today to go after my stalling starter issue. My plan was to go at it systematically, and to try to do one thing as a time, so that I could report back with the real find. I pulled the cowl and inspected all of the electrical connection, giving them a firm tug, to ensure that nothing was loose. My thoughts were that all of the positive leads were pretty robust, but that ground from the starter up just doesn't look that beefy. Also, given the fact that this ground lead is extended from the battery box, to the negative post on the battery with another small wire was not reassuring. Then I noted that the connection in the middle was held together by one of the tiny 21042-3 nuts, instead of a real high temp dash 3 AN lock nut. The connection was torqued properly, but I gave it another 1/8 turn, which was as much as I dare go with that tiny nut. Problem solved!! No more stall on start up. The next time that I take out that oil tank I will have access, and replace that tiny nut with a real AN-3 high temp lock nut. I'm a happy camper again. :)

Tom
 
todehnal said:
I finally had time today to go after my stalling starter issue. My plan was to go at it systematically, and to try to do one thing as a time, so that I could report back with the real find. I pulled the cowl and inspected all of the electrical connection, giving them a firm tug, to ensure that nothing was loose. My thoughts were that all of the positive leads were pretty robust, but that ground from the starter up just doesn't look that beefy. Also, given the fact that this ground lead is extended from the battery box, to the negative post on the battery with another small wire was not reassuring. Then I noted that the connection in the middle was held together by one of the tiny 21042-3 nuts, instead of a real high temp dash 3 AN lock nut. The connection was torqued properly, but I gave it another 1/8 turn, which was as much as I dare go with that tiny nut. Problem solved!! No more stall on start up. The next time that I take out that oil tank I will have access, and replace that tiny nut with a real AN-3 high temp lock nut. I'm a happy camper again. :)

Tom
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Congrats on taking a step by step approach! Approaching problems this way is easy for everyone! Getting to know the system and fundamentals is an excellent first step.

Happy to hear all it took was a new NUT!
 
todehnal said:
The next time that I take out that oil tank I will have access, and replace that tiny nut with a real AN-3 high temp lock nut.
Tom
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The MS21042 nuts are for higher temp installations and have pretty much the same strength and torque ratings as the larger AN363 all metal self locking nuts.

Good to hear you found the problem though.
 
rvbuilder2002 said:
The MS21042 nuts are for higher temp installations and have pretty much the same strength and torque ratings as the larger AN363 all metal self locking nuts.

Good to hear you found the problem though.
Click to expand...

Wow, looks are deceiving. I certainly would have picked an AN363, over an MS21042-3 for strength. That being the case, I may just do a "wait and see" on that battery ground connection from here. It sure is nice to have smooth starts........Tom
 
Electrical connections are black magic! When I was on the sub back in my Navy days we were doing a routine shift of load to the battery and it would not pick up load as we dropped DC output voltage from the generator. That got our attention because if the reactor shuts down submerged the battery is all you have until you get to the surface. After much troubleshooting we found a corroded cell-to-cell connection. When we kept dropping output voltage it would suddenly pick up the load. DC does some weird stuff!
 
RFSchaller said:
Electrical connections are black magic! When I was on the sub back in my Navy days we were doing a routine shift of load to the battery and it would not pick up load as we dropped DC output voltage from the generator. That got our attention because if the reactor shuts down submerged the battery is all you have until you get to the surface. After much troubleshooting we found a corroded cell-to-cell connection. When we kept dropping output voltage it would suddenly pick up the load. DC does some weird stuff!
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Interesting story about the sub! My starting issue was a bit strange as well. It would only stall on the first start of the day, which could be several stalls on that first start. After that, every start was text book. My engine compartment looks like new, but I guess heat expansion just created a better electrical ground connection at the battery box. Also, this condition has been there for a long time, and I just kept hoping for improvements with the break-in. I'm glad that it was that simple of a fix. What a terrific airplane!!...........Tom
 
It Is Not Fixed

Well, I must admit that I was incorrect when I said that I found the problem. I did get a couple of morning starts that appeared to be normal, but I am back to my original problem of several stalls of the first start of the day. Sorry to reopen this can of worms, but I just can't figure this out. I have cleaned, and reseated all of the +12 volt connections from the battery positive, through the master relay, through the start relay, and on to the starter. I also redid the grounds from the starter to that battery ground post. All with no joy. I am at a total loss, and it doesn't look that complicated. I still haven't added any additional ground wires, but it seems futile when we have hundreds of RV-12 flying happily with the original wiring. What am I missing??
 
Forgot to mention that I tried Doug's suggestion of giving it a spin with the ignition modules off. It didn't help. It still stalled. I am almost down to components. I need to eliminated the master, and start relays. The schematic shows that the 12 volts supplied to the starter goes through both the master, and the start relays, so either could be failing under large current draw conditions. I may try a jumper across the master first. If that doesn't show the problem, I may see if I can go directly to the starter with 12 volts, and see if it still stalls. I will get to the bottom of this. It's just a matter of time and patience. Thanks to everyone for your thoughts..............Tom
 
It might be time for more information / a more detailed analysis.

Are you basing your opinion that the starter is stalling, on the fact that the prop stops turning or that you know for a fact that the starter motor actually stops?

The reason I ask, is because failure of the sprag clutch for the starter drive is fairly common.
It will first start to show up when the engine is cold. After the first start of the day (if successful) it may act normally.

When the sprag clutch is failing, the starter motor is actually still turning, but the mechanical interconnect of the starter motor to the engine is slipping.
 
todehnal said:
Well, I must admit that I was incorrect when I said that I found the problem. I did get a couple of morning starts that appeared to be normal, but I am back to my original problem of several stalls of the first start of the day. Sorry to reopen this can of worms, but I just can't figure this out. I have cleaned, and reseated all of the +12 volt connections from the battery positive, through the master relay, through the start relay, and on to the starter. I also redid the grounds from the starter to that battery ground post. All with no joy. I am at a total loss, and it doesn't look that complicated. I still haven't added any additional ground wires, but it seems futile when we have hundreds of RV-12 flying happily with the original wiring. What am I missing??
Click to expand...

I admit, I have not followed this thread entirely to see if it has been discussed or not, but I was wondering if you have ruled out sparg clutch that is rather common with Rotax engines. The symptom looks more like a kick back than stalling but some times in manifest itself like a weak battery. It starts as an intermittent type issue and only gets worse to the point that a repair is needed. I used to have a coyote with a 912 engine in it that I replaced the sprag clutch twice but that was in a little over a 1000 hours of operation.
 
rvbuilder2002 said:
It might be time for more information / a more detailed analysis.

Are you basing your opinion that the starter is stalling, on the fact that the prop stops turning or that you know for a fact that the starter motor actually stops?

The reason I ask, is because failure of the sprag clutch for the starter drive is fairly common.
It will first start to show up when the engine is cold. After the first start of the day (if successful) it may act normally.

When the sprag clutch is failing, the starter motor is actually still turning, but the mechanical interconnect of the starter motor to the engine is slipping.
Click to expand...

Thanks Scott, for chiming in. On that morning first start, the prop stalls, and I get a sound that mimics a poor electrical connection, sort of like "zzzzzzt" Sorry about the sound effects. When that occurs, I let off of the key, wait a few seconds, and give it another try. I am also noticing a little slower than normal crank on that first start of the day, even after a second, or third activation. Subsequent starts seem normal. I sure hope that helps. I am unfamiliar with the sprag clutch. I thought a starter clutch failure would just allow the starter to spin, without turning the prop. Sort of like the old Cessna 150's when the starter engaging mechanism would stick.....Tom
 
todehnal said:
sort of like "zzzzzzt"
Click to expand...
Chances are the sound you are hearing is the sprag clutch slipping.

Unfortunately it is not a simple repair.... requires removing the engine from the airframe and removing rear accessory cover of the engine (supposed to be done by someone Heavy maint. certified)
 
rvbuilder2002 said:
Chances are the sound you are hearing is the sprag clutch slipping.

Unfortunately it is not a simple repair.... requires removing the engine from the airframe and removing rear accessory cover of the engine (supposed to be done by someone Heavy maint. certified)
Click to expand...

Wow!! That is certainly a depressing diagnosis. 120 hours, and it's been there for most of it's life. I just kept hoping for improvement with the break in. I really enjoyed the build, and the flight time. Not sure where I will to go from here.............Tom
 
IT'S A SAD SAY

It's a sad day...I have a lot of faith in Scott, and pay close attention to his suggestions, and analysis regarding the RV-12. He is truly an RV-12 guru. Way back, I was interested in a 3 blade prop. In fact, I had actually ordered, and received one, but Scott talked me out of installing it. I promptly returned it to Sensenich, and got the standard 2 blade. I have never been sorry that I did so. Many other helpful hints came from Scott during the build, and Scott has never steered me wrong. This was one time that I was hopeful that he was mistaken when he diagnosed my problem as being sprag clutch related. Yeah, I was in denial at first, and maybe still am, to a certain extent. Particularly since I have taken so much care with my 12. I installed soft start even before engine installation. I always keep a battery maintainer plugged in, always preheat in anything below 50 degrees, and I have never experienced kick back. Maintenance has been by the book, and I still have a catastrophic failure. Wow!! I took over 1300 build hours to build my 12, polishing every raw edge on every part, totally disassembled the airplane for paint, and followed every service letter to the "T" even though I built EAB. I transitioned from the D180, to the Skyview, installed all of the bells and whistles, including the latest ADS-B. Still, I wind up with a rare, but devastating failure. I'm sure that I will overcome the defeat, and end up doing whatever is necessary to get my 12 back to a flawless machine, but it may take a little time for me to get there. At age 76, it just seems to get a little harder to get started on another major setback. Thanks for everyone's help along the way. I will be sure to post anything of interest, or additional progress on this issue...........

Tom
 
todehnal said:
It's a sad day...I have a lot of faith in Scott, and pay close attention to his suggestions, and analysis regarding the RV-12. He is truly an RV-12 guru. Way back, I was interested in a 3 blade prop. In fact, I had actually ordered, and received one, but Scott talked me out of installing it. I promptly returned it to Sensenich, and got the standard 2 blade. I have never been sorry that I did so. Many other helpful hints came from Scott during the build, and Scott has never steered me wrong. This was one time that I was hopeful that he was mistaken when he diagnosed my problem as being sprag clutch related. Yeah, I was in denial at first, and maybe still am, to a certain extent. Particularly since I have taken so much care with my 12. I installed soft start even before engine installation. I always keep a battery maintainer plugged in, always preheat in anything below 50 degrees, and I have never experienced kick back. Maintenance has been by the book, and I still have a catastrophic failure. Wow!! I took over 1300 build hours to build my 12, polishing every raw edge on every part, totally disassembled the airplane for paint, and followed every service letter to the "T" even though I built EAB. I transitioned from the D180, to the Skyview, installed all of the bells and whistles, including the latest ADS-B. Still, I wind up with a rare, but devastating failure. I'm sure that I will overcome the defeat, and end up doing whatever is necessary to get my 12 back to a flawless machine, but it may take a little time for me to get there. At age 76, it just seems to get a little harder to get started on another major setback. Thanks for everyone's help along the way. I will be sure to post anything of interest, or additional progress on this issue...........

Tom
Click to expand...

Let's hope he is mistaken (a rarity). Do some better diagnostics on the electrical side, just to eliminate that - try that starter loaner. AND - if it is the sprag, why wouldn't that be warranty? There are a lot of 12 builders/owners on VAF, that should work in your favor.
 
Scott is probably right as usual. But before pulling the engine, do some tests to rule out an electrical problem. Connect a voltmeter between the POSITIVE battery terminal and the starter. Then crank the engine with the ignition switches shut off. If there is a significant voltage drop, then there is a bad connection or a bad contactor. Repeat the test while measuring the voltage between the battery negative terminal and the starter case.
 
Get some help???

I'd be glad to help you but I'm a long ways from you - but there has to be someone or a few someones who can assist you with the problem. Looks like you may need a Rotax Pro so find one and get going. You didn't get to 76yo by sitting on your hands. Best to you.
 
I thought I would weigh in here.

A damaged sprag clutch isn't very common. I does happen, but the cause is almost always poor maint. and or poor starting habits.
The sprag is made up as you see in the previous video of a spring and lugs or dogs if you want. They were only meant to turn in one direction. Rotating the prop backwards slowly stretches that spring out to where eventually the dogs won't engage in the normal rotation any longer.
In basic terms:
When the starter is energised and starts its rotation it engages the dogs on the sprag which lock up and then the crank rotates. When you have enough engine speed the plugs fire which may almost be instantaneously and then when the engine speed overtakes the starter speed the sprag clutch disengages. When you have damaged the spring that surrounds the dogs this fails to happen.

The common causes are:

#1 Kickback from starting. This is caused by poorly synced carbs, weak starter, old weak and out of spec plugs, poor starting habits and lack of gearbox maint. Throwing in a weak battery just makes some of these worse.
Reversing the prop rotation too much or too many times can also lead to this problem.

Poor carb maint, poor starting habits are #1 causes with lack of gearbox maint. right behind..
If you have an old engine with the black starter and you are having issues it may be advisable to change the starter out to the gold colored one that is a high torque starter.

If you have any kickback on starts you need to stop until you find the cause. It is a timely and expensive fix so the best thing is to prevent the issue from ever developing.
 
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Sink said:
I thought I would weigh in here.

A damaged sprag clutch isn't very common. I does happen, but the cause is almost always poor maint. and or poor starting habits.
The sprag is made up as you see in the previous video of a spring and lugs or dogs if you want. They were only meant to turn in one direction. Rotating the prop backwards slowly stretches that spring out to where eventually the dogs won't engage in the normal rotation any longer.
In basic terms:
When the starter is energised and starts its rotation it engages the dogs on the sprag which lock up and then the crank rotates. When you have enough engine speed the plugs fire which may almost be instantaneously and then when the engine speed overtakes the starter speed the sprag clutch disengages. When you have damaged the spring that surrounds the dogs this fails to happen.

The common causes are:

#1 Kickback from starting. This is caused by poorly synced carbs, weak starter, old weak and out of spec plugs, poor starting habits and lack of gearbox maint. Throwing in a weak battery just makes some of these worse.
Reversing the prop rotation too much or too many times can also lead to this problem.

Poor carb maint, poor starting habits are #1 causes with lack of gearbox maint. right behind..
If you have an old engine with the black starter and you are having issues it may be advisable to change the starter out to the gold colored one that is a high torque starter.

If you have any kickback on starts you need to stop until you find the cause. It is a timely and expensive fix so the best thing is to prevent the issue from ever developing.
Click to expand...

Sink, I appreciate you weighing in. I attended the first 2 Rotax classes at Sebring FL. and I am very meticulous with maint. I just checked the carb balance the other day, and it was spot on. Having my own set up make that function a very simple task. The engine runs very smooth, and starts are quick under normal circumstances. I have never cranked the engine backwards, always start on my "A" retarded ignition, and I don't recall ever having a kick back. I am now at 123 hours, and due for oil change in 2 hours. Not that it matters, but I burn ethanol free, and lead free 93 octane auto fuel exclusively. So, the cause eludes me, and I am having a hard time accepting the fact that it was caused by me, the only operator of the engine from day one. None of that changes the fact that I probably have a bad sprag clutch. My question is, do I need to take it out of service immediately, or can I continue to run it, knowing that the first start of the day will be met with a couple of stalls before I get a start?? I would be sick to learn that by continuing to fly, that I could incur additional damage to the engine.

Tom
 
Hi Tom,

I truely sorry for you problem. I know any issue is a PITA. Since these thing are man made you can have a bad part from time to time. I was just stating what the common causes were. These may have absolutely nothing to do with your individual issue.

You don't need to take it out of service because once the engine starts the sprag and starter are out of the run anyway, but just know one day the engine won't turn it all.

Are you absolutely sure it's the sprag. If the sprag is gone you can still hear the starter motor, but the engine won't move.

You may have just what you said, a bad electrical connection or even the solenoid. Since I can't hear it it's a little harder to diagnose.
 
Thanks Sink. I am NOT sure that it is the sprag. I even get this same stall condition when cold cranking with the ignitions off. The sound is like a screwdriver being inserted into a light bulb socket; "zzzzzzzzt"

Thanks for the comforting words about not causing additional damage if it is the sprag clutch. I'll be doing additional analysis, and will post any findings. I was hoping that one of the electrical components was known to cause this condition........Tom
 
Hey Tom - -

Can you video record the starting in a generally quiet area so we can SEE the prop and HEAR the starter sound ? Might help some of us understand the sound better that you are hearing.
 
JBPILOT said:
Can you video record the starting in a generally quiet area so we can SEE the prop and HEAR the starter sound ? Might help some of us understand the sound better that you are hearing.
Click to expand...

Good suggestion John. I'll try to do just that, and soon. I'll be at a bit of a disadvantage in posting it, but I am sure that I can figure it out.......Tom
 
Hey Tom - -

I'd take the top cowl off and with a helper hold the video device near the right side of the open engine compartment and face it toward the prop. Would not have to have mags on to avoid starting if it does turn over. I want to hear and see what you are seeing.
 
I have a little update. My action cam needed to be recharges, which delayed my video recording. So, I thought that I would try some additional tests. I used a jumper and spun the starter directly, with 12 volts directly to the starter. It spun the engine perfectly. Next, I used a long wooden dowel, and touched it to the starter solenoid, and had my wife turn on the master, leave the ignitions in the off position, and activate the key starter. The engine stalled (prop stopped) and I noted a profound vibration, and buzz from the start relay. After a couple of stalls, the buzz was gone, and the engine spun up normally. I am sure that the condition will be back in the morning. I think that I need to swap out the starter solenoid, but I was shocked at the price. The OEM starter solenoid is nearly $200, whereas Aircraft Spruce offers a replacement for under $30. Any thoughts??

Tom
 
Tom,

Before changing the relay, you may want to check the wire crimp and spade connector on the coil wire. The coil ground connection is through the mounting plate, make sure the relay is secure, if you have an older kit with the relay transfer adapter plate, make sure that is secure to the firewall too.

Check out this thread over on the Rotax-owner forum for info on non-Rotax replacements;

http://www.rotax-owner.com/en/rotax...enso-182800-1950-starter-solenoid-replacement

I don’t know how compatible this is to the Rotax supplied contactor. Here are the specs for the Rotax part;

Coil voltage;
12V nominal
6 V Min
18V Max

Contact;
75A continuous
300A 1-second

25% duty cycle

Mike
 
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