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Thread: Slow starter when hot

  1. #1
    Charlie Longley's Avatar
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    Slow starter when hot

    I just hung an O360. All the electrical components firewall forward are new except the master relay. New Skytec starter. New Concorde battery. When the engine is cold it spins up like a champ! When the engine is warm itís very balky.

    Any ideas?

  2. #2
    Charlie Longley's Avatar
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    I did a little reading and suspect the cable between the starter relay and starter.
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  3. #3
    wireweinie's Avatar
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    Check all crimps and connections on both the ground and positive cables first. When possible, check for a voltage drop across each section or connector.

    Web
    Life's tough . . . wear a cup.
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  4. #4

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    What Web said:
    A quick way to check cable connections,
    crank the motor for a min (mixture off) then run around and feel all the cable connections that are accessible - battery, solenoid, starter etc.. poor/loose/corroded connections will heat up and feel warmer to the touch. Kind of redneck but for field repair, good way to narrow things down.
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  5. #5
    Hardtailjohn's Avatar
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    You DO have copper cable installed and not aluminum, don't you? I remember the smoke rolling out of the cabin of our Warrior at work from that good ol' aluminum cable...in fact I saved a chunk that had melted.
    John

  6. #6
    skywagon8a's Avatar
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    What is the condition of the teeth on the ring gear? If they have a lot of rust on them or are excessively worn they can create an excessive amount of drag.
    Another but remote possibility could be related to ignition timing. If when the engine is hot, the clearances tighten up, the impulse fires the ignition a bit too early creating push back resistance. Do your impulse couplings click before or after top dead center? Remember that they are there to retard the ignition timing for starting. The fuel mixture will light off more quickly in a hot engine than a cold one thus if the timing is advanced a bit too much it will kick back instead of kicking forward.
    N1PA
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  7. #7
    Charlie Longley's Avatar
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    Quote Originally Posted by skywagon8a View Post
    What is the condition of the teeth on the ring gear? If they have a lot of rust on them or are excessively worn they can create an excessive amount of drag.
    Another but remote possibility could be related to ignition timing. If when the engine is hot, the clearances tighten up, the impulse fires the ignition a bit too early creating push back resistance. Do your impulse couplings click before or after top dead center? Remember that they are there to retard the ignition timing for starting. The fuel mixture will light off more quickly in a hot engine than a cold one thus if the timing is advanced a bit too much it will kick back instead of kicking forward.
    The ring gear is new. The engine was rebuilt by Watson Aero. They seem to have done a pretty good job! I would recommend them for an engine rebuild anyway. The timing is correct. I checked it during the Annual. I hung this engine on a clients 172M. I think the next one I do I am going to recommend all new electrical cables firewall forward. Bogert makes a set.
    Last edited by Charlie Longley; 07-09-2019 at 01:15 PM. Reason: Typo

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    Replace the master switch.

  9. #9
    skywagon8a's Avatar
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    Quote Originally Posted by skywagon8a View Post
    Do your impulse couplings click before or after top dead center? Remember that they are there to retard the ignition timing for starting.
    Quote Originally Posted by Charlie Longley View Post
    The timing is correct. I checked it during the Annual.
    Not the timing, the impulse couplings.
    N1PA

  10. #10

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    Does it just crank slowly or is it not firing off?

    My O360 would start fine cold but when hot it was like it was trying to run on one jug. It did start but the whole plane would sit there rocking while the O360 did a good job of impersonating one of those old hit-and-miss farm engines. Mechanic scratched his head as timing and impulse coupling were ok. I finally called Lycoming and was fortunate enough to get a tech that previously worked for a mag company. He immediately identified the issue as a cracked condenser (if I recall correctly). Problem solved.
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  11. #11
    Charlie Longley's Avatar
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    Quote Originally Posted by Mr. Ed View Post
    Does it just crank slowly or is it not firing off?

    My O360 would start fine cold but when hot it was like it was trying to run on one jug. It did start but the whole plane would sit there rocking while the O360 did a good job of impersonating one of those old hit-and-miss farm engines. Mechanic scratched his head as timing and impulse coupling were ok. I finally called Lycoming and was fortunate enough to get a tech that previously worked for a mag company. He immediately identified the issue as a cracked condenser (if I recall correctly). Problem solved.
    Both mags were overhauled 10 hours ago. I am going to troubleshoot the wire cables firewall forward when I get home. I am pretty sure that’s where the problem lies. The airplane sat outside in Hartford for a number of years and has come corrosion.

    Sky-Tec has a pretty good guide- https://skytec.aero/aircraft-starter...rmance-issues/

  12. #12
    Cubus Maximus's Avatar
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    I had the same issue and it turned out to be the ground. Spins happily away cold or hot now.
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  13. #13
    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by Charlie Longley View Post
    Both mags were overhauled 10 hours ago. I am going to troubleshoot the wire cables firewall forward when I get home. I am pretty sure thatís where the problem lies. The airplane sat outside in Hartford for a number of years and has come corrosion.

    Sky-Tec has a pretty good guide- https://skytec.aero/aircraft-starter...rmance-issues/
    seen mags(slick) only last a couple hours.....

  14. #14
    Hardtailjohn's Avatar
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    Found the old "reminder aluminum wire"....
    Click image for larger version. 

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    It's about a foot long, and wasn't outwardly in bad shape on one end.... I wont let any aluminum wire anywhere near me anymore.
    John

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