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Thread: runs excellent but starts hard after use

  1. #1
    Senior Member 2billydavies's Avatar
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    runs excellent but starts hard after use

    hey everyone,
    been awhile since I've posted but i'm at a loss and need a starting point. my 58' TR3a runs absolutely perfect. fires right up (initially), runs perfectly... doesn't miss a beat. I have zero complaints with the way she's been running this year since my rebuild.

    However... after she's warmed up she doesn't start very quickly at all if I shut her off. It takes many, many cranks to get her started back up and I just don't understand why. Sometimes (like lastnight) I'm afraid she isn't going to start at all.

    Any ideas on where to begin searching for the problem? Originally I thought vapor lock... but i'm just not believing it. I've never had an issue with that before, ever. but i just don't know at this point. It sounds like maybe it's flooding her out but after poking around I just don't see anything leading to that.

    Ideas/suggestions?? i should add that this ONLY happens after shes warmed up after use. no issues at all when starting the first time of the day or shes been sitting a while. very weird.
    thanks so much! happy holidays to everyone reading...

  2. #2
    Great Pumpkin TR3driver's Avatar
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    Re: runs excellent but starts hard after use

    Are you holding the throttle about 1/3 down, no choke? If you do get it started hot, does it blow black smoke at first?

    Looks like the high today in St Pete was 80F ... my guess would be percolation. Heat from the exhaust manifold (both radiant and conducted by air) toasts the bottom of the carbs, which of course is where the fuel jets are located. If they get hot enough to vaporize some of the fuel, it will blow vapor out into the carb throat and intake manifold, resulting in a very rich mixture.

    Few years ago, I went on a club run where we climbed a moderate (6%) grade for a few miles then stopped for a "biology break". Every single car struggled to get started afterwards, you never saw so muck black smoke!

    I installed one of Joe A's heat shields, which helped a great deal (but didn't entirely solve the problem). It's been suggested that adding more insulation would help more; my plan is to rig the electric fan so it runs for a bit right after a hot shutdown. Worth noting that MGA and Healey both came with heat shields as original, so the concept is at least period correct


    http://www.the-vintage-racer.com/ind...r3-heat-shield

    I did have to make some small adjustments: the hole for the vacuum advance line wasn't quite big enough for the compression nut, so I opened it up just a bit with a Dremel and mounted stone. A fine rat tail file would work as well.
    And the studs were just a bit short with the extra thickness of the shield and an extra gasket. Longer studs would be a better solution, but instead I removed the lockwashers and used some thin lock nuts instead. They work, just barely. (Ignore the extension sticking out, I was actually taking a photo of how to change the starter.)



    FWIW, here's what the front carb looked like. The rubber seal for the float bowl was so toasted that the burnt rubber was flaking off.

    Randall
    56 TR3 TS13571L daily driver
    71 Stag LE1473L waiting engine rebuild
    71 Stag LE2013LBW waiting gearbox rebuild

  3. #3
    Yoda CJD's Avatar
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    Re: runs excellent but starts hard after use

    If it starts well cold, but not hot...usually a sign of rich. If the floats are good and choke functioning right and not sticking, then try leaning the idle mixture a couple flats or so.
    John

    1955 TR2

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    Jedi Hopeful
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    Re: runs excellent but starts hard after use

    [QUOTE=CJD;1069040]If it starts well cold, but not hot...usually a sign of rich.

    That's probably it. Mine did that until I changed out the worn float valves. It floods when warm. No problem when cold.

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    Yoda NutmegCT's Avatar
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    Re: runs excellent but starts hard after use

    A naive suggestion, but for years I've heard it works.

    If it floods when warm, wouldn't the fix just be opening the throttle 100% (pedal to the floor) to clear it?

    Tom M.
    Mac & Phyllis Take a Trip: http://nutmegflyer.com/trip-details-daily-updates/
    History: 1976 MGB, 1959 Triumph TR3A, 1960 Mercedes-Benz 190b, 1958 Rambler American.
    Current: 1953 MG TD27318.

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    Jedi Knight
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    Re: runs excellent but starts hard after use

    That worked with a conventional carburetor. Don't know if it would work on an SU or Stromberg. Same with pumping the gas pedal. No accelerator pump.

  7. #7
    Obi Wan
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    Re: runs excellent but starts hard after use

    You could have low compression and when the motor is warm and the metal expanded it is worse.

  8. #8
    Yoda poolboy's Avatar
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    Re: runs excellent but starts hard after use

    Quote Originally Posted by NutmegCT View Post
    A naive suggestion, but for years I've heard it works.

    If it floods when warm, wouldn't the fix just be opening the throttle 100% (pedal to the floor) to clear it?

    Tom M.
    That would open the throttle disc, but I don't think it would make the air valve rise.
    DRIVE 'EM IF YOU GOT 'EM

  9. #9

    Re: runs excellent but starts hard after use

    Had the same problem with my 58. I added a length of Thermotec heat sleeve tubing around the fuel line around the thermostat area to the carbs. Problem solved.
    PeterK
    1958 TR3A 1966 TR4A both HVDA

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