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Thread: Any reason to keep my primer system?

  1. #1

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    Any reason to keep my primer system?

    It seems like the primer on the O-200 injects fuel at the same point as the accelerator pump...


    Made me think, why not just remove the primer and use the accelerator pump?


    I can't see an increased risk of induction fire... any thoughts?


    ​​​​​​​Thanks


  2. #2
    cubdriver2's Avatar
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    Couple reasons, when it's cold here even though my engine is plugged in and warm I need to leave the primer out about 3/8" to act as a choke for the first 20 or 30 seconds to keep it running.

    Reason 2 is if your hose from your gascolator get blocked or your carb has a flow restriction you can pump yourself home or at least to a more friendlier area.

    Reason 3 is if you foolishly run out of gas or enough fuel head pressure while over woods you might but be able to pump another mile or two and make it to an airport. Don't ask why I know this

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"
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  3. #3
    BC12D-4-85's Avatar
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    Prime the cylinders not the induction spider. If the intake tract is cold most of the fuel will turn to liquid and then run down and out of the carb. Most cylinders have a drilled and tapped 1/8 NPT hole on the top over the intake valve for a special restricted primer fitting (AN4022-1). That fitting vaporizes the fuel better than a plain hole and prevents excessive air intake/lean running if the primer line breaks.

    Four cylinders primed is better than one. If you want to use the accelerator pump give it a few pumps then quickly pull or crank the engine through several prop turns to get fumes to the cylinders. Again, top priming next to the intake valve is better.

    But like Glen notes some of us have had to depend on a primer to act as a choke or keep the fires burning when the carb fuel bowl is empty or restricted.

    Gary

  4. #4
    Bill Rusk's Avatar
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    I have no primer and it works fine. Get the engine turning over, then pump the throttle a couple of times and it lights off. The only disadvantage is there is not much way to prime the engine if you have to hand prop it. Different strokes for different folks. Do what ever works for you.

    Bill
    Very Blessed.

  5. #5
    aktango58's Avatar
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    It should prime to the cylinder heads, not the carb.

    Though Bill gets away without it so far, I have had plenty of times I needed the primer to get started.

    As an example, we were ferrying a 172 north one time with a two cylinder primer. It would not start! We did everything, then finally got some stove pipe and ran heat into the engine compartment, (just frosty on the ground- not really cold). the owner installed a 4 cylinder primer once home and has never had another issue.
    I don't know where you've been me lad, but I see you won first Prize!

  6. #6
    mvivion's Avatar
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    Quote Originally Posted by Bill Rusk View Post
    I have no primer and it works fine. Get the engine turning over, then pump the throttle a couple of times and it lights off. The only disadvantage is there is not much way to prime the engine if you have to hand prop it. Different strokes for different folks. Do what ever works for you.

    Bill
    Just make dang sure that engine is turning over before you use the accelerator pump. I’ve seen one airplane burned to the ground by someone trying to start with the accelerator pump.

    i MUCH prefer a primer system and USE IT to start. If you have fuel injection, how you going to prime that engine to prop it?

    As George said, put the fuel in the cylinder, not the lower induction. One little back fire can ruin your day. Doesn’t happen often, but it’s really bad when it does.

    MTV

  7. #7

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    I don't have a primer in my Cub and no starter. Has worked fine for about 25 years once I got the sequence down.
    I have an IO360 and a wobble pump in my Pitts. I never use the wobble pump.
    I pull it through 12 blades with the mixture rich, it starts building fuel pressure at about 8-9 blades. Go mixture lean and it holds fuel pressure until I'm ready to start and it starts on the second blade, like clockwork.
    As a wise man once said "Different strokes for different folks".

  8. #8
    fancypants's Avatar
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    Those of you that are priming your small Continentals directly at the cylinder head, which cylinder are you plumbing your primer to? Just one or all four?

    I might be forgetting, but I can't recall ever seeing any C90's or O-200's with primer lines running up on top of the cylinders. Pretty sure some cylinder castings aren't even threaded for the primer nozzle.

  9. #9

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    Quote Originally Posted by cubdriver2 View Post
    Couple reasons, when it's cold here even though my engine is plugged in and warm I need to leave the primer out about 3/8" to act as a choke for the first 20 or 30 seconds to keep it running.
    How's that work? Or do you mean you give it a little pump during the first 30 seconds to keep it running. I have experienced that in the cold.

    Quote Originally Posted by cubdriver2 View Post
    Reason 2 is if your hose from your gascolator get blocked or your carb has a flow restriction you can pump yourself home or at least to a more friendlier area.
    I always wondered why primers were generally not filtered by the gascolator, but this wouldn't work if it was.

    Quote Originally Posted by cubdriver2 View Post
    Reason 3 is if you foolishly run out of gas or enough fuel head pressure while over woods you might but be able to pump another mile or two and make it to an airport. Don't ask why I know this

    Glenn

    Well those are enough reasons for me!

  10. #10

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    People preheat a lot better now than they used to. I'd tell you if you need primer to keep it running you need better preheat practices but that said, I used to use primer regularly to keep it lit when cold starting. No amount of throttle jockeying will keep a really cold engine running. Reiff pretty much solved that problem.
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  11. #11

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    Quote Originally Posted by mvivion View Post
    Just make dang sure that engine is turning over before you use the accelerator pump. I’ve seen one airplane burned to the ground by someone trying to start with the accelerator pump.

    i MUCH prefer a primer system and USE IT to start. If you have fuel injection, how you going to prime that engine to prop it?

    As George said, put the fuel in the cylinder, not the lower induction. One little back fire can ruin your day. Doesn’t happen often, but it’s really bad when it does.

    MTV
    Yeah, that's why the baby Continental primer system is kind of a joke. As Fancypants said, there's no option for cylinder prime, to my knowledge. So the primer puts fuel in a difficult to atomize and dangerous spot.

  12. #12

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    If you're idle settings are on the low end throttle plate acts like a choke

  13. #13
    n40ff's Avatar
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    Seems to me some of you are confusing Lycomings and Cont.'s
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  14. #14

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    I would also like to inquire as to where Zaylor operates from?
    I flew Conn. winters allot.
    When I had my C-150 I recall pre heating it a time or two. I generally just fired it up cold.
    I did however richen and lean the idle mixture seasonally.

  15. #15
    mvivion's Avatar
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    Quote Originally Posted by Zaylor View Post
    Yeah, that's why the baby Continental primer system is kind of a joke. As Fancypants said, there's no option for cylinder prime, to my knowledge. So the primer puts fuel in a difficult to atomize and dangerous spot.
    My last C 90 had cylinder prime. Millennium cylinders.

    MTV
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  16. #16

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    Quote Originally Posted by Carey Gray View Post
    I don't have a primer in my Cub and no starter. Has worked fine for about 25 years once I got the sequence down.
    Out of curiosity, what is you sequence to start your cub?
    I also have no starter or primer. Three shots of throttle and the third blade it usually starts. If itís very cold, it might take a min.....Pierce, txpacer and BTV witnessed my cold weather workout routine.

  17. #17

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    Quote Originally Posted by KevinJ View Post
    Out of curiosity, what is you sequence to start your cub?
    I also have no starter or primer. Three shots of throttle and the third blade it usually starts. If itís very cold, it might take a min.....Pierce, txpacer and BTV witnessed my cold weather workout routine.
    Cold, I give it a couple of pumps on the throttle and pull it through about a dozen blades, one shot of throttle and it'll start on the third blade. Warm, I give it one shot of throttle and it'll start on the third blade. I always start the engine with the mixture at idle cutoff. It'll run for a few seconds which is long enough to make sure everything is OK. When I'm sure my head is not planted where it shouldn't be, the mixture goes in.
    In my opinion, the propeller is there to pull the airplane forward and to kill you if you're not careful.
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  18. #18

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    Quote Originally Posted by CharlieN View Post
    I would also like to inquire as to where Zaylor operates from?
    I flew Conn. winters allot.
    When I had my C-150 I recall pre heating it a time or two. I generally just fired it up cold.
    I did however richen and lean the idle mixture seasonally.
    Alaska. I preheat when needed. It's not that I have any trouble starting the plane. I just thought the primer was silly considering the location.

  19. #19

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    I will double check, but I don't think I have any pipe plugs in my cylinders. That's what I am looking for right? I would much prefer cylinder prime. They are shown in the IPC though, hmm.

  20. #20
    BC12D-4-85's Avatar
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    Quote Originally Posted by Zaylor View Post
    I will double check, but I don't think I have any pipe plugs in my cylinders. That's what I am looking for right? I would much prefer cylinder prime. They are shown in the IPC though, hmm.
    If you remove the primer from the induction spider it offers the opportunity to install a manifold pressure gauge to that fitting. Small Continentals are prone to carb ice and a MP gauge will drop off if ice forms faster than rpms.

    Threaded primer plugs with square heads above intake valve:
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  21. #21
    cubdriver2's Avatar
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    The Clipper we were flying skis with today had a carb.problem last time out and quit running, he pumped it back to a safe landing

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"

  22. #22
    aktango58's Avatar
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    Quote Originally Posted by cubdriver2 View Post
    The Clipper we were flying skis with today had a carb.problem last time out and quit running, he pumped it back to a safe landing

    Glenn
    Glenn, respectfully, have you considered flying a plane that the engine does not quit while airborne?

    Seriously, I might not have thought about the primer for that- great learning.

    Having the primer is another tool in the tool box. That one time you are out, and get yourself into a spot longer and the plane cools a bit more than planned, it is going to get dark and your choice is to be stuck for DAYS inside a tent in the storm or start it now and get gone... best to have it and not need it.

    Only my opinion.
    I don't know where you've been me lad, but I see you won first Prize!
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  23. #23
    BC12D-4-85's Avatar
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    My first engine out involved trying the primer - O-360 PA-12 - it would keep the prop spinning but not enough to maintain altitude. Two point primer with throttle cracked some, however a four point would have been better. Try it sometime. When cracked but not pumped it'll run rich and rough (not rare, unlike the whisky). Who hasn't forgot to lock the primer at least once?

    Gary
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  24. #24

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    I'm surprised that hand prop guys aren't the biggest advocates FOR 4 cylinder priming. It makes starting so much easier. That's no different for key starting. I always want my plane to fire as quickly as possible. A primer system has a clear advantage for that. The colder the engine the bigger the advantage.

    I know a very seasoned old pilot that told a story about a power loss in flight. He figured out he had carb water problems and used the primer to feed clean fuel into the cylinders so he could make it to a strip.
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  25. #25
    Steve Pierce's Avatar
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    Quote Originally Posted by cubdriver2 View Post
    The Clipper we were flying skis with today had a carb.problem last time out and quit running, he pumped it back to a safe landing

    Glenn
    What engine? The staock carb on the O-235 on the Clipper didn't have an accelerator pump.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
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  26. #26
    cubdriver2's Avatar
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    Quote Originally Posted by Steve Pierce View Post
    What engine? The staock carb on the O-235 on the Clipper didn't have an accelerator pump.
    Yup, I asked him today and that's what it's got. Must be lite, it performs very well

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"

  27. #27

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    Quote Originally Posted by Carey Gray View Post
    Cold, I give it a couple of pumps on the throttle and pull it through about a dozen blades, one shot of throttle and it'll start on the third blade. Warm, I give it one shot of throttle and it'll start on the third blade. I always start the engine with the mixture at idle cutoff. It'll run for a few seconds which is long enough to make sure everything is OK. When I'm sure my head is not planted where it shouldn't be, the mixture goes in.
    In my opinion, the propeller is there to pull the airplane forward and to kill you if you're not careful.
    Tried your idle cutoff start procedure today. Works just as you say. Thanks again

  28. #28
    cubdriver2's Avatar
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    Quote Originally Posted by Carey Gray View Post
    Cold, I give it a couple of pumps on the throttle and pull it through about a dozen blades, one shot of throttle and it'll start on the third blade. Warm, I give it one shot of throttle and it'll start on the third blade. I always start the engine with the mixture at idle cutoff. It'll run for a few seconds which is long enough to make sure everything is OK. When I'm sure my head is not planted where it shouldn't be, the mixture goes in.
    In my opinion, the propeller is there to pull the airplane forward and to kill you if you're not careful.
    I bet if you give it 2 pumps of the throttle and go Hot it will start on the third blade

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"
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  29. #29
    BC12D-4-85's Avatar
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    Another tip is to prime sequential cylinders in order of firing if priming less than four. That way you get two burns in a row to get things turning.

    Gary
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  30. #30

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    Quote Originally Posted by cubdriver2 View Post
    I bet if you give it 2 pumps of the throttle and go Hot it will start on the third blade

    Glenn
    It would start, but I kinda like making sure there's compression and all the cylinders feel even. At least on the first start of the day.

  31. #31
    hotrod180's Avatar
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    My C180 only primes two of the 6 cylinders.
    My buddy's has a primer distributer block mounted on top of the engine and does all 6.
    I thought mine was cobbled up but the IPC shows it both ways.
    Some day I'm gonna re-plumb mine with one of those 6 way blocks.
    Cessna Skywagon-- accept no substitute!

  32. #32

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    Confirmed that my cylinders don't have the holes for cylinder-prime.

    I will keep my primer thanks to the good advice on possible emergency uses. Thanks everyone

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