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Cranky Starter II - (No Swingy, No Starty)
Hello. I have read as many ?cranky starter? and ?starter problem? threads as I can find, but I am running out of ideas to solve my starter problems on my Lycoming IO-320 standard compression engine. I have a Hartzell 2-blade C/S metal prop with 1 Slick Mag & 1 Lightspeed CDI ignition module. Total time on engine is 300 hrs, and I use Phillips 20w50 X/C oil.
My Symptoms: My key ignition switch takes 3-4 attempts to get the prop to move past the compression stroke before it will swing the prop to start. (The engine starts up just fine, once the prop is swinging.) My Actions & Results To-Date: Replaced 7 yr-old 12V Odyssey PC680 battery with new Odyssey PC680 battery 4-mos. ago. Result: Same start-up symptoms with my existing permanent magnet Sky-Tec 149-LS Lightweight starter. Cleaned all cable and wire connections from battery to starter - positive and negative. Result: Same start-up symptoms. Replaced starter with new series-wound Sky-Tec 149-NL starter 3 weeks ago. Result: Same symptoms with new starter. Replaced Starter Contactor with new Starter Contactor 2 weeks ago. Result: Same start-up symptoms. Replaced Master Contactor with new Vans Master Contactor this past weekend. Result: Same start-up symptoms. Note: Output lug of master contactor is joined to input lug of starter contactor with 3-1/4" length, double-thickness of copper bus bar. Measured Voltage at various locations, per Sky-Tec?s trouble-shooting guide: 13.0 Volts (No-Load) at battery, 11.0 Volts (When Prop is Cranking) at battery, 10.6-10.7 Volts at starter (When Prop is Cranking), No measurable resistance on major power and ground cables. Above Voltage tests were with newest Odyssey battery, alone. Hooked old & new Odyssey batteries in parallel and retested. Result: Same start-up symptoms. (Once the prop did start swinging, it did swing with more authority.) Talked to Alan at Sky-Tec support this morning. He is perplexed, too, as 10+ Volts at the starter should provide plenty of torque to start without stalling. However, he requested I make the following additional test: ?Disconnect the starter contactor?s positive cable from the new starter, and hook up a 12V starter caddy or known good 12V battery directly to the starter?s positive lug and good ground to eliminate potential upstream problems.? The above test sounds simple enough. But frankly, the idea of making contact with a cable end that will have 100-200 Amps flowing through it scares me to death! I imagine some arcing sparks would occur, too. Can someone suggest a safe way to complete this test? Do you have any other suggestions that I may be missing? I have nearly run out of parts to replace. Thanks, Dale |
What about with the igniton off? How well does it swing then?
How about with the plugs removed? Does your ground cable connect to the engine case, or does it run right up to the starter and bolt to its case? |
Try adding a heavy ground strap between the engine block and the firewall or the negative battery post. Had the same happen to me on a cessna one time, bad ground to engine. I tried doing it with jumper cables just to test the theory, it didn't work, had to put on a strap.
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Have you checked the key switch? Had similar problem. Discovered as long as I didn?t turn the key to the stop it started every time.
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Check your ground cable/strap from battery or ground block to the engine block. the continuity/resistance of this is just as important as the positive side. Your symptoms are typical of low current, which can often be traced to high resistance somewhere in the circuit, assuming the battery is sound. The initial crank take quite a bit more energy than once its spinning.
Larry |
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Or even more basic. Verify that the airplane even has one. This is a commonly missed detail. |
Ground your voltmeter to the starter if you didn't already.
Easier than checking the physical grounds is when measuring voltage to the starter it should be in reference to the ground of the starter housing, or the voltage across the starter.
I ran a separate wire w/ground for this purpose in my trouble shooting. Safe |
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Ground Straps & Key Switch
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I have two ground cables. One approx. 8" mesh ground strap originates from the battery's negative post and terminates to the firewall. The 2nd approx. 18" #2 ground cable originates from the engine block to a 2nd location on the firewall. I have measured "0" ohms resistance between: battery negative post & ground cable #1 end, battery post & ground cable #2 at firewall, and battery post and starter housing. However, I can try running a substantial cable directly from the starter case to the negative battery post. Maniago, I'm not sure how I would disable the ignition, short of removing all plug boots, as the ignition is part of the key-switch. KAdriver You raise an interesting possibility with the key-switch that I haven't yet explored. I have never really paid attention to where my key position is when the prop stops. This will be an easy one to check this evening. Dale |
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I would also test voltage drop on the starter. Place one probe on 12v terminal on starter and the other on ground then crank and observe reading. Give the results to skytech. With everything you have done, I also would be at a loss. You either have a source/transport issue that is limiting current or your starter is unable to convert that power to rotation. Your ignition switch is not an issue. Either the contactor closes or it doesn't. Pretty binary. Actually, I take that back. The starter contactor draws 4-5 amps on the coil. If you had a significant resistance in the switch, it is possible that it can't pass enough current to fully close the contactor. However, this would likely result in occassional chatter of the contactor. Larry |
Single point ground
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Ed Holyoke |
If I read the OP correctly, there is now a new NL starter on the ship - which should spin a std compression 320 fast enough to taxi around with. If the heavily geared NL is struggling to get over the hump, but have 10+ volts at the starter post then you must have a really bad ground. Might try a single jumper from the neg battery post to the starter case (leaving the originals in place) and see if it improves performance.
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KADriver,
That problem should manifest noticeably different symptoms, if you know what you're seeing and hearing. If the start contacts of the ignition switch are flaky and dropping out, you should also hear the start contactor drop out along with the switch contacts, and the sounds from the engine/starter will be different. You'd also see battery voltage return to near no-load levels. To the OP, Fat welding cable is very flexible, readily available locally, and serves well in many homebuilts as battery/starter/ground cable. The only thing that should be in the ground path from starter/engine case to the battery negative should be a brass or copper feedthrough bolt on the firewall, if the battery is aft of the firewall. There have been cases where starters (and alternators) have had poor grounds due to heavy paint or powdercoat on the appliance, the attachment bits, or the motor itself. When doing your measurements, be sure the meter negative is directly on the battery post (not the clamp or bolt). Work your way along the ground path, on both sides of all joints, with the meter positive lead. You should never see more than a half volt or so (in the extreme) between any point from starter case and the battery negative post, while the starter is under load. |
ETX900
Probably not the same problem. I had a PC680 that was just struggling to turn my angle valve engine over so I swapped it out for a ETX900. Now I save fuel by taxiing to the runway with the mags off. 😜
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Key Switch Technique - May Be the Solution!
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After the 1st successful start, I intentionally shut the engine down to try a 2nd time. The same key technique gave me the same success. I know one sunny day doesn?t make a Summer, but I am encouraged. I will keep everyone posted. Dale |
Toss that flakey switch and install a couple of toggles and a pushbutton. :)
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Key switches look cool, do multi functions, give the appearance of security, but have an insidious history of exactly what youve encountered. |
Great it appears to work now, but can anyone explain why? If the primary symptom is the inability to crank over the first compression stroke, then how does an intermittent contact on the key switch do that? The key activates the starter solenoid, and the starter solenoid sends the big power to the starter. the starter solenoid is either on or off. Bad contacts in the key switch will not alter the amount of power running through the main plunger contact in the starter solenoid. The only way I can see this happening is if the solenoid makes/breaks contact because of the poor signal from the key. But this would manifest as a buzz or chatter of the solenoid, which would be obvious to the pilot.
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Are you suggesting that the ability of the solenoid to pass hundreds of amps through the massive contact points are determined by the resistance in the small solenoid plunger coil circuit? How is this possible? The two circuits are electrically isolated.
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My Key-Switch Theory
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This may be a bit premature, but I now believe that my key switch is breaking the 12V circuit to the starter contactor, when it is turned to the extreme right. During the transition to this position, my prop starts moving, because the starter contactor is energized. Then, it's de-energized due to the faulty switch. I never heard starter contactor chatter during my starting attempts. Previous to last night, it would take 3-4 attempts at turning the key to get the prop past the compression stroke. My theory is, once past the compression stroke, the prop finally had enough spin momentum to start the engine, despite the key eventually breaking the starter contactor circuit. BTW, My key-switch is ACS P/N 11-03170 (A-510-2 FAA-PMA Approved). The key assembly was installed by the builder 12 years ago. Dale |
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IOW, what Dale said above ought to make sense if you consider that the switch worked correctly for a while, but then started "acting up". This kinda stuff happens all the time with sliding contacts - they get burned and oxidized at the edges. And I suspect youre in an edge condition. Eitherway, if you can make it function as Dale describes, that ought to clue you that its the switch internals themselves, and again, take apart your switch and you'll discover exactly whats going on. Noone else can say for sure with your particular switch, just speculate. |
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None of us can see/hear what you do. But low starter voltage will present somewhat different symptoms from a bad switch. If it's the switch causing the problem, the start contactor will either be engaged, or not engaged, or chattering. It *won't* cause a low voltage condition at the starter. So there will either be full start voltage, no start voltage, or pulsed voltage. Pulsed voltage caused by a chattering switch isn't likely to effectively move the prop.
If the switch is making and then breaking, the engine will likely still come up against a compression stroke; once moving, 'flywheel' effect will try to keep it moving. But you'd likely see the prop recoil slightly after hitting the 'spring' of compression. You can see the same effect if the battery is actually too low to push a blade past compression; the prop recoils when you release the start switch. Low voltage at the starter would likely drive the prop against the compression, and hold it there (until the switch is released; see above). |
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This is one of the failure modes of poor starter performance and is why the starter troubleshooting guide walks you through measuring voltage drop across all connections and components while passing a lot of Amps (while cranking). |
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Keep in mind the voltage sag when the starter engages. That same voltage sag will be present on the starter solenoid. If your start switch has bad contacts, the voltage getting to the starter solenoid my be adequate to hold it shut with no voltage sag, but once the starter drops buss voltage, the starter solenoid drops out from under voltage. I hate Cessna style legacy key igntion switches. I alway use toggle switches for the ignitions and a push button for the stater solenoid. Carl |
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Larry |
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If it tried to climb the compression stroke and gave up (solenoid dropped out), that's completely different than really slow to climb the compression stroke (low amperage at the starter), and you drop the key to try again. That's the trouble with diagnosis by internet - Words have very specific meanings to different people. |
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Larry |
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To clarify, my symptoms were such that with each twist of the key-switch, I would see the prop turn 20-30 degrees, then stop. At the peak of compression, it was like watching the prop move 20-30 degrees in slow-motion. Once past the compression stroke, the next turn of the key would spin the prop with momentum, just a blade or two, to start the engine. As a side note, I disassembled the original starter contactor, after I replaced it a couple of weeks ago. It showed minimal signs of arcing between the copper disc and two power lugs. This is what lead me to believe I might have a faulty master contactor. More testing is needed to definitively say that the key-switch is the culprit. But, I do believe this is the weak link in the system. Once replaced, I will be very interested to see the condition of the key-switch internal contacts. Dale |
It really is difficult to troubleshoot over the internet, and after a bunch of back & forth, sometimes it's hard to remember the original symptoms. :-)
quote from the 1st post in the thread: Measured Voltage at various locations, per Sky-Tec’s trouble-shooting guide: 13.0 Volts (No-Load) at battery, 11.0 Volts (When Prop is Cranking) at battery, 10.6-10.7 Volts at starter (When Prop is Cranking), No measurable resistance on major power and ground cables. Above Voltage tests were with newest Odyssey battery, alone. Hooked old & new Odyssey batteries in parallel and retested. Result: Same start-up symptoms. unquote. If the above quoted measurement is correct, and voltage at the starter terminal isn't dropping below ~10.5 volts *under load*, then I'm having a really hard time seeing how either of the contactors or the start switch is the culprit. If there was high resistance anywhere on the positive side of the circuit, then the voltage at the starter terminal would be much lower than what was measured; the starter windings would appear as a virtual short to a high source-resistance current source. What we don't know is the voltage measurement between the starter case and the battery negative post while the starter is under load. (hint, hint) It's worth remembering that a lot of stuff has been swapped out. Stuff can get moved, even if the problem is in the ground path. That could easily explain why things are working well at the moment. Remember those no-start situations with that old car, when wiggling the battery connections 'fixes' it? |
Key Switch - The Culprit
Just an update...We now have a trend!
I went flying again this evening, and the starter never hesitated once in 4-5 turns of the key-switch - cold or hot-start - just by turning the key only far enough to engage the starter. I'm sure I could duplicate the previous symptoms by turning the key all the way to the CW stop. However, I was busy enjoying watching the 149-NL spin the prop with gusto. That was a welcome sight for me. I would go so far to say that I would have the same successful results with my previous LS starter, my old starter contactor, and old master contactor, knowing what I know now. However, that train has left the station, and my ticket-to-ride cost 1/2 AMU. Sigh... Dale |
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Interesting how things work out...
I have the same ACS key switch in my plane, and for 260 hours it has worked flawlessly. This past weekend I experienced the same symptoms that were laid out here in this thread while starting up for an IFR training flight. If the key was rotated hard against the stop, the contactor dropped out. Back off just a hair and the contactor picks up and the starter engages. I guess I'll replace the rotary key switch with two toggles and a pushbutton as others have recommended. |
Since you have confirmed good voltage to the starter, try a simple test, put a test light clip on the starter +, ground the test light up on the firewall to where you can observe it while cranking, start engine while watching test light, if the engine stops keep the key in the same position while looking at the test light, did the light come on while cranking? then did the light go out when the prop stopped? remove clip from starter and work your way back through the power path to narrow it down.
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Here's a data point that *might* come into play if the start switch itself is failing.
A lot of early starters had a mechanism that the spinning starter used to drive the bendix forward into the ring gear. In those old systems, the start switch contacts only had to handle a few amps to pull in the starter contactor. A lot of newer starters use a big solenoid (an actual solenoid) that pushes the bendix forward and at the same time, supplies the high current contactor switching at the starter. This solenoid takes a lot more current to activate than a simple contactor. IF (again, IF) you have a later version starter with that solenoid on its side, and you use an old style ignition/start switch designed to drive a contactor, then you MAY see shorter than normal life in the start switch contacts. Of course, the same thing would apply if you use a low current push button to activate the same starter. IIRC, B&C sells a start PB rated at around 15-20 amps. Worth what you paid, etc... Charlie |
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