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Slowwwwww To Start

Discussion in 'Early CJ5 and CJ6 Tech' started by 71CJ54WD, Feb 8, 2021.

  1. Feb 9, 2021
    ITLKSEZ

    ITLKSEZ Hope for the best, prepare for the worst

    Liberty Lake, WA
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    My old Ford has always been a bear to prime. If it sits for more than a few days, it has to crank until the battery is almost dead to fire. I tried a new mechanical pump and a new carb (mainly to address other problems), but it never affected the hard start issue. I finally switched to an electric pump, and problem solved (or diverted). Those chatterbox pumps are noisy when they have no resistance, then they quiet down when the bowl is full, so you can tell when it’s ready to start. Now it fires immediately, even after sitting through a 6-month winter.
     
    dozerjim and tcfeet like this.
  2. Feb 9, 2021
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
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    Your Ford has a Holley or an Autolite (Motorcraft)? The Motorcraft carbs are well-known for draining the bowl quickly, whether it's evaporation or leaking around the power valve. The accelerator pumps are also a well-known site for leakage.

    I think Pete is right that no carburetor will sit indefinitely without the bowl drying out. Then you will need something like a minute of cranking to fill the bowl before it will start. Personally I prefer starting fluid to dumping gas down the carb, since it will mostly be vapor and won't wash down the cylinders (I presume). Just a shot of starting fluid will run the engine for a couple seconds and greatly speed up bringing fuel to the float bowl.

    Replacing the mechanical pump with an electric has been discussed many times before.
     
  3. Feb 9, 2021
    ITLKSEZ

    ITLKSEZ Hope for the best, prepare for the worst

    Liberty Lake, WA
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    2100.
    It sits for 6 months, then gets run every 3-4 days all summer, so lifting to hood and mowing through starting fluid was less than ideal. The cheap pump switch was the ideal solution for my application.
    Turds gonna turd. No point in polishing it.
     
    dozerjim and Fireball like this.
  4. Feb 9, 2021
    Keys5a

    Keys5a Sponsor

    Florida Keys
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    My Triumph has a Buick 215 (Rover version) with a Rochester 4 jet. This is a close cousin to the Dauntless. It does exactly the same; first start of the day, it likes a lot of cranking, after that, it fires right up. I have an electric fuel pump. If I turn the key to "on" before I twist to start, I listen to the fuel pump run. When it changes tone after about 20-30 seconds, the bowl is full. Two jabs of the throttle, it fires right up.
    Those old Rochester carbs drain the bowl when sitting (2 bbl or 4bbl like mine). I always see weeping around the throttle shaft, but never have figured exactly why the bowl doesn't stay filled. It doesn't evaporate overnight, though a hot engine does contribute a little.
    -Donny
     
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  5. Feb 9, 2021
    Norcal69

    Norcal69 Out of the box thinker 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Northern California
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    Allot of engine builders will tell you that the first startup after a complete drain back (Sitting for more than a day) its a wise idea to build oil pressure before firing the engine. Even more reason to let it crank with a Buick oiling system.
     
    FinoCJ likes this.
  6. Feb 9, 2021
    jzeber

    jzeber Well-Known Member 2022 Sponsor

    Morgan Hill, Ca
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    My 71' had a 231 and 2 barrel Holley. That thing ran flawlessly the entire time I owned, sideways, upright and even on its side. But if it sat for more than a week I had to prime the carb every time. Pour a little gas down the carb and it would start right up. If I took it out for a few days of wheeling it never happened again. For some reason starting fluid would not work, had to be gas.
     
  7. Feb 9, 2021
    Walt Couch

    Walt Couch sidehill Cordele, Ga. 2024 Sponsor 2023 Sponsor 2022 Sponsor

    cordele, Ga.
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    The 2G is a great little carb. If the bowl is not cracked then the only way it can loose fuel is down through the power valve. The shaft with spring pushes down on the power valve at rest which closes the valve in the power valve. This seals any gas from escaping the fuel bowl. If the shaft vacuum piston is hanging up in the sleeve any at all it might over-ride the spring hold down and allow the power valve to stay slightly open which will allow drainage of the fuel bowl.
     
  8. Feb 9, 2021
    colojeepguy

    colojeepguy Colorado Springs

    At the foot of...
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    This may be more of a problem than you think...before you get carried away with anything else, put fresh gas in it....alcohol free if you can get it.
     
    Rick Whitson likes this.
  9. Feb 10, 2021
    OnlyOneDR

    OnlyOneDR Member 2023 Sponsor

    R
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    My '69 K5 has a 2GV on it; same thing would happen if it sat too long and that is even after a rebuild. Of course long right now is an understatement; I have not fired it up in nearly a decade.
     
  10. Feb 16, 2021
    71CJ54WD

    71CJ54WD Sponsor

    DC
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    So after much moping about, I've decided to block off the mechanical pump and go electric. Can anyone recommend a pump that they've run and can verify won't flow too much to the carb. Also, the return line off the pump...what did you do?
     
  11. Feb 16, 2021
    John Gedde

    John Gedde Been around the block once or twice...

    Middle Island, NY
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    I had the same problem on mine... Turned out the fuel pump arm was worn into the cam eccentric... Since I rebuilt the motor and replaced the cam/fuel pump, it works OK now. That is except if it's been sitting. The gas evaporates out of the carb bowl pretty quickly, so it takes a bunch of extra cranks to get her primed. I'm pretty sure you can peek in the fuel pump to block 'hole' and see if your cam is worn. Mine was almost worn round!

    John
     
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  12. Feb 16, 2021
    71CJ54WD

    71CJ54WD Sponsor

    DC
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    Not only did I take a peek in there I put my borscope in there and verified that the eccentric is A-OK. On all my old cars I've always had an electric pump so I don't know why I was acting allergic to this Jeep getting an electric pump.
     
    John Gedde likes this.
  13. Feb 17, 2021
    boopiejones

    boopiejones I can’t drive 55

    California east bay
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    I have a 198 with a Rochester 2G with a purolator 12S pump. It’s a facet brand with a purolator sticker on it.
     
  14. Feb 17, 2021
    71CJ54WD

    71CJ54WD Sponsor

    DC
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    Ok thanks - the service manual says 3.75 psi. I can easily find a pump close to that rating but what is everyone doing with the return line that would remain? Do I block it off?
     
  15. Feb 17, 2021
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
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    The return line is metered. In the later Jeeps with a special fuel filter (one inlet, two outlets) the metering is an orifice that limits the return volume. Not sure what kind of metering the V6 has, but it will be there. Depending on which pump you choose, the return may or may not starve the engine of fuel. If the pump you choose has a similar or higher volume rating as the mechanical pump, then the return will work fine. This is separate from the maximum pressure.

    However, the return becomes less useful with an electric pump. The return's main purpose is to lower the temperature of the fuel in the lines, and prevent vapor lock. With an electric pump, the location of the pump back by the tank means that any fuel vapor in the lines will be compressed under increased pressure and move forward, rather than expand under reduced pressure and cause fuel starvation (I presume). Electric pumps are often used to overcome vapor lock problems.
     
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  16. Feb 17, 2021
    boopiejones

    boopiejones I can’t drive 55

    California east bay
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    i do not have a return line - just a single line feeding the carb. Pump is directly below the tank. Fuel filter is just before the carb. Most of it is connected via hard lines, with short sections of polyurethane hose to ease installation and replacement of the filter.
     
  17. Feb 17, 2021
    Mr Vaughan

    Mr Vaughan

    i gotta agree with pete, don't expect it to start like it's a brand spanking new supercar. it's an old jeep, with an old engine. dill with it, pickle
     
  18. Feb 17, 2021
    71CJ54WD

    71CJ54WD Sponsor

    DC
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    Interesting - I have a single in and single out fuel filter. Always have. Could there be a backflow prevention in that 1 in 2 out filter? I could try to plumb in that filter first or just go electric and have fuel at the carb on demand a little better.
     
  19. Feb 17, 2021
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

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    Nothing magic about the 1-in 2-out filter. I have cut them open, and it's like any other filter, with an extra outlet metered by a tiny orifice. You are supposed to put the 2nd outlet up so the fuel filter won't drain through the return line. It'll still work with the 2nd outlet low.

    There are valves in the fuel pump that are required for the pump to work. These should prevent the fuel lines from draining back, but if you calculate it, the volume in a 5/16" pipe is small. Plus it's easy to test - take the fuel hose loose at the filter and crank the engine. I expect it will spurt almost immediately. If not, you likely have a bad fuel pump.

    Anyway, I think the back flow idea generally is mistaken. There is no siphon action from the float bowl back to the fuel pump. The float bowl won't drain unless there is a leak - like a hole in the bucket - or the fuel evaporates. Different carburetors have different designs with different opportunities for leaking.
     
  20. Feb 17, 2021
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2024 Sponsor 2023 Sponsor 2022 Sponsor

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