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Zenith Carburetor Question 1992

Discussion in 'Other Construction/Demolition Equipment' started by M1687, Jul 11, 2018.

  1. M1687

    M1687 Well-Known Member

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    I have a 1992 Zenith Carburetor on a Ford LSG 423 (similar to the picture shown below). My question is that if the machine sits overnight or longer, there is a Viton tipped valve at the fuel inlet that gets stuck closed thus not allowing fuel to enter the carburetor and giving me a no start. I take it apart and reassemble and it starts and works for the day. Any ideas on what might be causing this? There is a tiny spring inside the Viton tipped valve also. Do I need to change this assembly out etc? The valve doesn't show any visible wear. Any thoughts?

    upload_2018-7-11_9-57-3.png
     
  2. funwithfuel

    funwithfuel Senior Member

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    I would be more suspicious of the fuel shut off solenoid. It's the doodad with the wire hanging off of it. Carefully remove and clean the chalky junk from behind the needle. Maybe a little hogwash if available near you. Since you're stuck in the mid-west like me, you probably got that crappy blended gasoline. Let it sit one season and you're screwed . Either run it dry when you're done or start getting a fuel stabilizer.
    Good luck.
     
  3. M1687

    M1687 Well-Known Member

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    When I have this condition I usually take both apart. If the fuel shut off solenoid is faulty would it cause the inlet valve to close? In other words when I have the crank-no start the fuel line is pressurized between the fuel pump and the carburetor so no fuel is entering the carburetor at all. Yes I'm in the Midwest. The only good thing is that my local gas station sells "recreational" fuel which basically doesn't have any ethanol in it. That doesn't mean that the damage wasn't already done by the previous owner(s) but I use this fuel to help avoid any future problems. Have you ever rebuilt one of these carbs? Any do's, don'ts, or lesson's learned?
     
  4. funwithfuel

    funwithfuel Senior Member

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    Yeah the shut-off valve essentially keeps the bowl from flooding over with fuel as the needle and seat wood with a float if memory serves the shut-off valve essentially closes Off fuel to I believe they call it an emulsion tube when you experience the no-start condition the simplest thing to do would be to have someone cycle the key to the on position while you have your hand on the shut-off solenoid you should feel a faint click they are Stone simple to rebuild not many moving Parts mostly ports and orifice you can clean them with a welding tip cleaner and put it all back together in maybe a half of an hour
     
  5. Tinkerer

    Tinkerer Senior Member

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    Try using it with the electric cut-off removed and see what happens.
     
  6. funwithfuel

    funwithfuel Senior Member

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    Fuel will pour out
     
  7. OFF

    OFF Senior Member

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    I agree with what's been said so far. Highly doubtful the problem is a sticking needle & seat on the fuel inlet. The engine will run as long as there is fuel in the float bowl. Genie part number for that carb repair kit is #28714 if you need it.
    More likely the electric fuel shut-off valve is not operating properly. Make sure it's got power whenever the ignition is on, and you should be able to feel/hear it click on & off as ignition power turned on & off.
     
  8. funwithfuel

    funwithfuel Senior Member

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    Reading offs post again I realized something very silly on my part I should have mentioned to verify that your engine block ground is clean and tight I never asked if the engine would stall out when it's already running if this is only a no-start condition I would be more concerned with a ground fault just because your starter cranks does not necessarily mean that your block is properly grounded make sure you run a ground from the starter or a starter mounting bolt to the block and to the chassis.
     
  9. Tinkerer

    Tinkerer Senior Member

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    FWF I don't doubt for a second that would occur.
    But what is different about that particular carburetor that the float / needle valve assembly would not stop fuel flow ?
    High pump pressure ?
     
  10. funwithfuel

    funwithfuel Senior Member

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    The solenoid stops fuel not from feeding the carburetor but from reaching the intake manifold it blocks off the emulsion tube which draws fuel up into the throat of the carb
    You still have fuel in the bowl your needle and seat still dictate the fuel level within the bowl but this little shut off solenoid is a positive stop so you cannot have dieseling or run on because it takes away the fuel supply all together
     
    Tinkerer and Delmer like this.
  11. Tinkerer

    Tinkerer Senior Member

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    That makes perfect sense to me. I learned something new again.
     
  12. M1687

    M1687 Well-Known Member

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    Thanks for all the feedback. This machine sat for a while before I acquiried it and I remember when I first got it started it would not turn off because of a stuck fuel solenoid. Currently once its running the valve performs as necessary. Is the thought that its not getting enough electricity or the solenoid is getting weak and not opening up during start up or when cold?
     
  13. funwithfuel

    funwithfuel Senior Member

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    No. Same thought as originally posted. Crud behind the plunger. Residue from garbage fuel.
    The follow up was if any of the mentioned symptoms had occurred, you may have had a ground fault. Once spent several days trying to troubleshoot a quick attach on a skidder. Back and forth, back and forth spinning my wheels getting no where. Power everywhere. Until I put my meter at the plug together. No ground. Found bad ground from starter to chassis. Engine was grounded, started , ran and charged. No accessories. Stupid oversight I try not to repeat