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Thread: #3 cylinder not responding

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    Jedi Warrior Lukens's Avatar
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    Question #3 cylinder not responding

    Greetings,
    Haven't been posting for some time because I bought a C3 Vette (don't hate me).
    My TR3 has been idle for 3-4 months. Had a hard time starting it, but it finally fired with starting fluid. It ran well enough to get it to my garage with partial choke, but it had a definite miss. Today I replaced the plugs, had good spark to all cylinders, but didn't respond to pulling #3 plug boot. Checked compression and measured +/- 150 on all four.
    Could it be carburetion? The back carb is opposite #3 and #4 but shares a runner with the front carb so I doubt the manifold is selective. Any ideas as to what's causing #3 to not respond?
    Thanks in advance.
    Lukens

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    Yoda
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    Re: #3 cylinder not responding

    Is the #3 plug wet with gas when you pull the plug out? Could be the rear carb float needle sticking either closed or open..

    David
    TR3A TS75524L

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    Yoda PeterK's Avatar
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    Re: #3 cylinder not responding

    Could be that #3 plug wire is not fixed to the distributor cap. Check the set screw inside the cap for #3. Also the plug boot is tight as some twist on to the cable
    PeterK
    1958 TR3A 1966 TR4A both HVDA

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    Obi Wan Sarastro's Avatar
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    Re: #3 cylinder not responding

    You've done a perfect troubleshooting job up to this point. You've isolated it to one plug wire. So, why even think about the carbs?

    The problem, now, has to be the ignition wire, its connectors, or something at the cap associated with that wire's connection. Look into the plug and distributor-cap connections, make sure there is a good, solid connection with the wires. Or just try a new wire.
    Steve Maas
    1966 Triumph TR4A, restoration completed Aug. 2020: http://www.nonlintec.com/tr4a
    1952 MG TD, restoration completed 2014, sold 2016: http://www.nonlintec.com/mgtd
    1960 Austin-Healey "Bugeye" Sprite, sold 2010: http://www.nonlintec.com/sprite
    1967 Porsche 912: http://www.nonlintec.com/porsche

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    Jedi Warrior Lukens's Avatar
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    Re: #3 cylinder not responding

    Thanks Peter and Steve. I thought like you too, but I've got got a spark tester that mimics a plug and I get good stong spark. Since the car sat and needed ether to start, I'm leaning towards carb problems. To be continued.
    Russ

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    Yoda
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    Re: #3 cylinder not responding

    So # 3 is non- compliant—well ---is the engine so clean, the spark plug ground is not grounding? With these cars, it can almost always be a carb problem, but I usually go to the carbs last. Are you saving no fuel is going into # 3? Or maybe a piston is leaking somehow, so that the cylinder is too weak to detect a difference when the plug is pulled?

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    Yoda CJD's Avatar
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    Re: #3 cylinder not responding

    Good compression, good plugs, good wires. It sounds like a good brisk drive around the hood would do it good. While possible, it is unlikely that the rear carb would fuel #4 without fueling #3. Give it a good run to clean the old fuel out of the bowls.

    If it back fires out the tail pipe, you have narrowed it to an ignition issue. If it pops out the carbs...then itís a mixture (carb) problem.
    John

    1955 TR2

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    Yoda PeterK's Avatar
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    Re: #3 cylinder not responding

    Did you put oil on the plug threads or an insulating anti-sieze? Just thinking, my brother did that once, and prevented grounding.
    PeterK
    1958 TR3A 1966 TR4A both HVDA

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    Yoda Geo Hahn's Avatar
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    Re: #3 cylinder not responding

    Quote Originally Posted by Lukens View Post
    ...didn't respond to pulling #3 plug boot...
    I take it that pulling the plug wire from #4 had the usual effect?

    I would certainly remove the tops of the fuel bowls and examine the contents as these engines will run surprisingly well on 2 cylinders and if one carb is dry strange things may happen.

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    Yoda Geo Hahn's Avatar
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    Re: #3 cylinder not responding

    Quote Originally Posted by Lukens View Post
    ...didn't respond to pulling #3 plug boot...
    I take it that pulling the plug wire from #4 had the usual effect?

    I would certainly remove the tops of the fuel bowls and examine the contents as these engines will run surprisingly well on 2 cylinders and if one carb is dry strange things may happen.

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    Jedi Warrior Lukens's Avatar
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    Re: #3 cylinder not responding

    Bingo... DividApp and Geo Hahn. Pulled both carbs and gave them a good cleaning and tune. Running like the tractor motor it is.
    Thank you all for your advice.
    Russ

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    Yoda
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    Re: #3 cylinder not responding

    Hello Russ

    Great when a plan comes together.

    Back on the road again.

    Savid
    TR3A TS75524L

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    Yoda martx-5's Avatar
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    Re: #3 cylinder not responding

    Are you using Sta-Bil?? When I didn't use it, I always had hard starting and lousy running problems after a long period of disuse. No problems since adding it to the fuel.

    And, thumbs up on the C3...
    Art
    '58 TR3A TS236xxL
    '92 Mazda Miata -- Supercharged
    '07 Mazda RX-8
    '11 Mazda CX-7

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    Re: #3 cylinder not responding

    There is a Utuber, "FarmProject" that has some interesting videos comparing different engine products to see which work the best. He has one on fuel stabilizers that is pretty interesting:

    https://www.youtube.com/watch?v=UvS_D4_lF5U

    What I found interesting is the ethanol fuel we use does go bad rather fast. But, I totally forgot about how the old straight fuel would dry into a varnish that was a bear to clean out of carbs. The main lesson is that any un-capped fuel will go bad from sitting...and all of the fuel in our carbs is vented, so it will go bad sooner than later.
    John

    1955 TR2

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    Yoda PeterK's Avatar
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    Re: #3 cylinder not responding

    Yup same lesson for 4 cycle lawn motors. I keep my tanks full, especially when storing over the winter. I never use Stabil-type products, just keep them full of fuel. And they always (almost) start 1st or 2nd pull in the Spring. I do the same thing for the cars. Some states allow non-ethanol gas sales but not around here.


    Quote Originally Posted by CJD View Post
    There is a Utuber, "FarmProject" that has some interesting videos comparing different engine products to see which work the best. He has one on fuel stabilizers that is pretty interesting:

    https://www.youtube.com/watch?v=UvS_D4_lF5U

    What I found interesting is the ethanol fuel we use does go bad rather fast. But, I totally forgot about how the old straight fuel would dry into a varnish that was a bear to clean out of carbs. The main lesson is that any un-capped fuel will go bad from sitting...and all of the fuel in our carbs is vented, so it will go bad sooner than later.
    PeterK
    1958 TR3A 1966 TR4A both HVDA

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    Yoda martx-5's Avatar
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    Re: #3 cylinder not responding

    Quote Originally Posted by CJD View Post
    ... . The main lesson is that any un-capped fuel will go bad from sitting...and all of the fuel in our carbs is vented, so it will go bad sooner than later.
    I have the vent tube from the fuel tank capped off, and during storage, I put a small plastic bag between the tank opening and the fuel cap, pretty much closing the system. That helped a lot, as the gas smell in the garage would sometimes get pretty bad before I started doing that. The gas in the fuel bowls of the carbs evaporates within a week or two, so I don't worry about that. If I start the car after more then a couple of weeks of sitting, I always prime the float bowls with the hand lever on the fuel pump.
    Art
    '58 TR3A TS236xxL
    '92 Mazda Miata -- Supercharged
    '07 Mazda RX-8
    '11 Mazda CX-7

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