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Thread: Hard starting

  1. #1

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    Hard starting

    Any suggestions???
    I have a 150hp SC and it just started starting really hard.
    I try 3 primer shots and a full throttle then retard the throttle all but about 1/4 of the way open crank and crank
    then reprime 2 times and crank and crank
    then I go and get the battery charger so I can crank some more
    it does finally start but this is getting old and its only 35-40 degrees what will happen at 20 degrees??
    thanks guys for the imput!!!

  2. #2

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    the way I was told to start a 150 hp is SLOWLY "pump" or "advance" the throttle while cranking the starter. Every cub I have tried that way fires on the first pump when temps are > 50 and second to third "pump" when temps are <50 - never used the primer. But - having said that I recognize all are different beasts so have you tried sweet taking to it while trying to start it - works with my wife.

  3. #3

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    try pulling the engine through by hand w/ mags off. do you hear the impulse coupling(s) click? no? maybe a broken impulse coupling spring.
    bendix mags have a 500 hour check on impulse coupling wear
    when was the last time the mags had anything done to them?
    perhaps the internal timing of the mag has changed drastically due to cam follower wear. seems points aren't lasting like they used to.
    what kind of starter? some of these newer designs spin a weak engine fast enough the impulse coupler no longer engages, eliminating the retard function needed to create a hot spark for starting. does it even try to run, or does it just sit there and crank?
    last spark plug service?
    how is the idle once you manage to get it running?

  4. #4

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    starting

    If your mags and plugs and cylinders are all in good shape & not part of the problem then try it this way. Leave the primer alone! Pump the throttle 3 times all the way stop to stop, then with it all the way closed crank the engine. If it does not start in 5-6 blades give it a couple more jabs of throttle. If it still does not start something is not quite right. This is only for a cold engine. Depending on the carb it might only take one or two but 3 seems to get most of them going. Remember not to advance the throttle much after it starts or you will give it to much air and it will quite. Some engines start or will continue running better with the carb heat on.
    Dave

  5. #5
    Steve's Aircraft (Steve)'s Avatar
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    Had one recently where the left mag coil got weak. Replaced coil and easy starts resumed.

    Steve

  6. #6

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    Like several others here, I suspect the mags. In addition to making sure everything is set correctly (internal timing and clearances), make sure that they still have magnetism. A mag shop can remagnetize them without much or any disassembly.

    Hank

  7. #7
    mvivion's Avatar
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    I agree that this sounds like a mag problem.

    That said, I never pump the throttle on one of these things BEFORE I start cranking it over. Do so, and you are simply using the accelerator pump to spray fuel into the bottom of the airbox, basically. At least that's where the fuel goes in an updraft carb when using the pump.

    Now, crank it over with the starter, THEN pump the throttle twice, and you are sucking fuel/air mixture into the engine through that updraft carb.

    I would never use the accelerator pump on one of these engines without engaging the starter first. I have seen one burned to the ground doing so.

    I do agree that priming really isn't necessary if you use the accelerator pump properly.

    MTV

  8. #8
    T.J.'s Avatar
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  9. #9

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    I just went through the same thing with a 180 Cub, and it turned out that the impulse coupler was bad. The funny thing was it snapped just fine and timing was right on. Once it was runnign it ran fine. I was beginning to doubt my starting technique too. When I replaced the mag, presto, good starts again. On mine, only one mag has the impulse coupler. It just kept getting worse, though, until one day in the middle of nowhere, It would Not start. Good Luck......popsdory

  10. #10

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    I agree with Mike - I have seen a couple of carb fires, although they ended well. Henceforth, my students will not pump the throttle unless the engine is cranking. Big problems with the radials - those pumps put out a quart at a time!

  11. #11

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    Thanks guys i'm off to the airport to try again with the wealth of knowledge you all provide.... with any luck i'll be back in the air today!!!!

  12. #12
    aktango58's Avatar
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    Not to disagree, but could be plugs in shape also.

    I would check plugs first, as it is easy to pull a couple, then the mags.

    If an 0320 does not start easy, something is wrong!
    I don't know where you've been me lad, but I see you won first Prize!

  13. #13
    bearsnack
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    Check your primer also, all of the lines.
    Disconnect one at a cylinder and give a couple shots to see if your delivering fuel. Check all of the lines for leaks.

  14. #14
    AkPA/18's Avatar
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    Smitty

    They wouldn't happen to be slick mags would they?? Just curious.

    Mark
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    Takeoffs are optional--Landings are mandatory

  15. #15

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    Hard starting

    Mike I agree pumping the throttle before cranking COULD start a fire but in 20 some years of flying many many different 18s I have Never had one lite off even in hot summer weather with a hot engine when I used to spray with one. Once you get your engine figured out 3 blades and its running every time. Now I wish I could say the same for hot starting a IO 520 in a cessna spray plane. They will start every time if you flood them a bit but you better have a good battery in case they light off and keep cranking until it starts.
    How would you manage your method if you had to hand prop it?

    Dave

  16. #16
    mvivion's Avatar
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    Dave,

    Hand prop with cold engine: THree shots of prime. Gas in cylinders, not induction air box.

    Hand prop with warm engine: Crack the throttle 1/2 to 1 inch, and crank it. Never had one refuse to start that way when warm.

    It is VERY easy to flood these engines when warm.

    MTV

  17. #17
    SuperCub MD's Avatar
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    The primer does inject the fuel higher in the intake than the accelerator pump, BUT fuel will still run down into the airbox if you over prime just as much using either system. The primer really doesn't do much of a better job than the accelerator.

    It is usually best to start with as little prime as possible. It's easy to add more if needed, much harder to get it back out if you flood.

    I preheat a 320 anytime the temp is below 40 (oil temp needle on the peg).

  18. #18

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    I agree with Mark as winter is almost running full throttle If you have access to a preheat under 40 degrees do it, gives you time to do that thing,,,,, I think, they call it Prelight, Take a leak, finish your Cup O Joe, Take another leak... I would love to see another thread on preheatin with no electricity, I think I'll post tomorrow, there has to be new ways to do it Jet boil, Coleman, 20# propane, etc. etc...
    Matt

  19. #19
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    Winter has moved in today around here. Temps have been dropping all morning. 25* at 6 a.m. now its down to 12* at 11:25 a.m. .So... Pre-heating will be required now . Never had any trouble starting if I've preheated. But did have a little prob last winter on a fishing trip up at Lake of the Woods. Temp was at -14 and was unable to preheat. Took a while to get her to fire while hand propping. I Only run 2 primer lines to the rear cylinders and only give it minimum amount of prime as I've had more trouble with too much fuel than not enough.

    How many of you always use the mixture to kill the engine ? Would it make any difference if you didn't and simply used the mag switch to kill it ?

  20. #20

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    Quote Originally Posted by david jaranson
    How many of you always use the mixture to kill the engine ? Would it make any difference if you didn't and simply used the mag switch to kill it ?
    It's a safety thing. Using the mixture to kill the engine provides some degree of safety in case one of the mags is "hot".

    Hank

  21. #21

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    Hankster: Not meaning to highjack the thread here, but many years ago I figured out that for short shutdowns, better to shut off the engine with the mags, at a dead-idle. Then you know FOR SURE that both mags are grounding out, AND it starts on the first blade. Just like my old A-65 Continental, with the Stromberg.

    And not meaning to pick a fight either, but shutting down with the Mixture tells you NOTHING about whether the mags are actually grounded. Anyone ever had one kick back after mixture shutdown?

    Any of you fellers/gals with more knowledge about this stuff than me (which is almost everyone here) please jump in, explain to me the error in my thinking and experience. Mags/Mixture/Master. Then recheck before you walk away, and recheck when you get back.

    Thanks. cubscout

  22. #22
    RedEye's Avatar
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    cubscout,

    That would be my thinking also. I've done it before for the very reasons you mention and had no probs starting.

  23. #23
    RedEye's Avatar
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    hankster,

    From a safety stand point, yes I usually use the mixture for shut down, but I also use the mags from time to time to ensure I dont have a hot mag.

  24. #24

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    Cubscout and David,

    I can't disagree with either of your statements. I was citing "conventional wisdom". After all, it does take both fuel and spark to make the engine run. Starving the engine of fuel, then killing the mags removes both.

    Are there valid reasons to follow other procedures? Sure.

    Hank

  25. #25
    Dave Calkins's Avatar
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    Smitty, let us know how this went for you.

    guys, a couple of points:

    1. don't pump the throttle until you start the prop is spinning, without air movement up the induction, that fuel is sitting in your airbox.

    2. I have started an induction fire on an 0-470 in a C-180.....but only on a day with temps below freezing. This sucks, so now I make sure to have the right prime, and I will keep that starter spinning if the pig happens to pop, but not continue running.

    3. I agree that most likely Smitty172 has an ignition system issue.......if this has developed slowly, probably magneto e-gap related, especially if he's a Slick man.

    4. Agpilot-Dave, number 2 above(!) for me it seems it's a cold-weather thing, 'cause who ever needed lots of prime on a warm day? P.S. On cool or cold days, I go 3 full shots of prime on 4cylinder Lyc.'s and 5 shots on 0-470's for the first start.

    5. I agree with SuperMD, that prime will run out of there if you let it. Prime, and start cranking, don't be sitting around in there fiddling with stuff while your prime runs back out the airbox.

    MY last point ......NUMBER 6. Killing an engine with idle cut-off mixture is great, but knowing the mag switch is grounding is also very nice......especially if you will be doing the hand-prop gig. So............right before I shut 'er down at the end of the day, I will momentarily kill with mag switch, then bring 'er back to life...then.........pull the mixture out and she's done. This is force of habit from performing the Airworthiness Directive on some switches that require the sign-off mechanic to check the switch operation......I check the switch operation EVERY time on my personal airplanes. So should you!. All of you, every man, WOman, and child who runs these things.


  26. #26
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    Hard starting

    Back in the early 1960's I had a PA-20 with a 0290 that I flew about 300 hrs ayear. Most of the flying was long trips and I flew into Mandan, ND. on a Sunday nite and put my plane in a hanger. I had an annual inspection about 4 months prior to this flight. On the following Sat. afternoon I rolled the plane out for the return trip home. It wouldn't even fire on one cly. I ran the battery down trying to get it started! Went in to the FBO and wanted to borrow a battery. The mechanic said it was the spark plugs. I said Bul#$% , it ran perfectly coming in last week. Got the battery and ran that dead too without it firein once ! I was pissed !! Went back to the mechanic and he said change the plugs. Again I argued with him. He asked how many hours on the plugs and I estimated 700 to 800. He said change the plugs.!! I said I never heard of all the plugs going bad at one time in any engine . Finally he said look - I'll give you new plugs, you put them in and if it doesn't work , bring them back and I won't charge you a dime!! I put the plugs in and turned the mags on ,hit the starter and it didn't turn a half a prop blade and it was running like a top!! Boy did I feel stupid!! Hard starting can very well be the spark plugs !!

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    I know this thread is ancient, but I'm curious what the cause ended up being. Something else to consider, too, is when it's REALLY cold the fuel doesn't want to vaporize. I was taught that around freezing you should prime then let it set for 30 seconds to a minute to let it vaporize, then start the fire. Anyone have thoughts?

  30. #30
    this would be a title NimpoCub's Avatar
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    Since I don't know what the fuel nozzle does or looks like, I wonder if there's any difference between a swift prime & a slow one. IE: Does a sharp push vaporize the fuel better 'n a slow one??
    Nimpo Lake Logan... boonie SuperCubber
    200mi (300km) from nearest stoplight... just right! - "Que hesitatus fornicatus est"

  31. #31

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    Quote Originally Posted by NimpoCub View Post
    Since I don't know what the fuel nozzle does or looks like, I wonder if there's any difference between a swift prime & a slow one. IE: Does a sharp push vaporize the fuel better 'n a slow one??
    If you push too hard/fast you'll cavitate the plunger and end up replacing the seal thingie...This I know and wish I didn't.
    Remember, These are the Good old Days!

  32. #32
    this would be a title NimpoCub's Avatar
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    Thanks. I'll remember that. All the girls tell me the same thing.
    Nimpo Lake Logan... boonie SuperCubber
    200mi (300km) from nearest stoplight... just right! - "Que hesitatus fornicatus est"

  33. #33
    cubamigo's Avatar
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    Check and see if the p leads are going to the correct mag. If you have a key start switch one mag is shut off. Perhaps you are trying to start on the non impulse mag.

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