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Thread: Running rich

  1. #1

    Default Running rich

    After my adventures in this thread( thanks everyone for their advice ) http://vb.foureyedpride.com/showthre...-Idling-issues
    it turns out my original fuel pump had been pumping fuel into the oil the entire time I was tuning the carburetor. Good thing I checked the oil before I took it for a spin. It had about a gallon and a half of fuel in it.
    One fuel pump and an oil/filter change later I was back at square one since I was actually getting fuel.
    Problem I have now is I am running super rich. Or so I presume since I have puffs of black smoke coming out of my exhaust and when I rev the engine it looks like a Diesel engine.
    I had to screw the idle screw in all the way to get it to idle. Could this cause this?
    Could I lean it out by adjusting the float levels lower?

    I have checked and rechecked and rechecked for vacuum hoses that are disconnected or are broken and have been unable to find anything. I do suspect a vacuum leak in addition to over fueling.

    Any advice is appreciated.
    Last edited by MrFoMoCo; 07-29-2018 at 07:41 PM.
    1985 Mustang GT convertible triple white
    Stock survivor

  2. #2
    FEP Super Member
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    Start at the basics ,
    Float level , I presume you have a holey, I did not read your other thread .
    If so , with engine idling , which may be hard in your case , fuel should just barely trickle out the screw /sight hole on the side of the float bowl .
    2
    Check the power valve , make sure it is not blown , should probably do this first .


    3 car should idle , with mixture screws turned 1.5 turns from bottomed lightly .
    Start there , check back with your results .
    clowns to the left of me , Jokers to the right

  3. #3

    Default

    Stock unmolested Holley 4180c. Just rebuilt it with a Holley kit.
    1985 Mustang GT convertible triple white
    Stock survivor

  4. #4

    Default

    Quote Originally Posted by ashley roachclip View Post
    Start at the basics ,
    Float level , I presume you have a holey, I did not read your other thread .
    If so , with engine idling , which may be hard in your case , fuel should just barely trickle out the screw /sight hole on the side of the float bowl .
    2
    Check the power valve , make sure it is not blown , should probably do this first .


    3 car should idle , with mixture screws turned 1.5 turns from bottomed lightly .
    Start there , check back with your results .
    Yup, pretty much nailed it. Two things will cause your issue, floats are way too high or a blown power valve. You can run the floats super low and it will still run fine (it will fall on it's fave when you are too low). You could turn them down one turn and see if it helps.

  5. #5
    FEP Senior Member
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    May 2016
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    Lake City Pa 16423
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    Look down into the carb, and make sure fuel isn't coming out of the boosters when idling. That would indicate a float too high or a stuck open needle and seat.

  6. #6

    Default

    ^ What Don said ^

    ^ What ashley roachclip said ^, either while idling again at the slowest speed she'll idle at, or after some cranking where the fuel pump will have filled the fuel bowls to where the floats are adjusted to. If fuel is gushing out the sight plugs on the passenger side, try lowering the float/s, by loosening the set screw and turning the 5/8" nut clockwise... while running, open whichever primary/secondary throttle you are presently trying to adjust, to use up some fuel and see whether the fuel level goes down in the float bowl and stays down where you've lowered it to... if no matter how far you lower the float/s, the fuel level/s are still too high... either the float/s isn't floating any longer, or there's debris blocking needle and seat/s, or it/they are sticking open somehow...

    Opening the primary idle speed screw doesn't cause anything, but compensates with more air for the excess fuel (and also adds too much more fuel with the transfer slots when the primary idle speed is set too high, rendering the idle circuit and the idle mixture screw settings useless)... the excess fuel at idle that's happening for... we don't know why yet...

    "The power valve is blown!"... has been overblown for decades, a go-to myth, and rich idling or low speed is often a sign that something else isn't right, but check it as procedure to eliminate the possibility if there is rich idling and no apparent sign of where the extra fuel is coming from, because the vacuum exit for power valve vacuum is invisible with the carburetor on, at the underside right beside the front and center screw that holds the base plate to the main body. So, if there's an issue with the power valve's diaphragm or gasket, fuel gets pulled straight into the intake manifold, invisibly. Either pull the vacuum hoses from the front of the 4180's base plate with the engine shut off right after you've run the engine, and look/feel for signs of raw fuel there or in the vacuum hoses (the pickups for these in/under there are also right near the above mentioned screw). Sometimes you'll get raw fuel there if the power valve (or it's gasket) are no longer sealing vacuum to the backside and fuel to the front side, either due to a defective power valve or incorrect installation (gasket seal) or the power valve's diaphragm has actually been "blown" by one hellacious backfire. The other (better) method to check if the power valve or gasket is allowing fuel through at idle, is to disassemble the primary float bowl and metering block back off the carburetor, and look for signs of fuel wetness on the backside of the power valve and in the vacuum chamber for it in the main body... there should be none. If there is signs of fuel in those areas, check the gasket seal installation (power valve and gasket installation should be done with the metering block held in a horizontal position and the power valve and gasket screwed in upward into the metering block, so the gasket stays in place where it should on the power valve)... if the gasket/seal appears fine, then the power valve's loose or the diaphragm inside it is defective or "blown"... replace it...

    After that ^ , see that all the air bleeds are clear, and re-establish a baseline with the idle speed screw reduced again and the idle mixture screws (are they accessible? ... if not, yikes... but anyway, make sure where the tips of those mixture screws are and the small holes into the throttle bores are clean and clear... carburetor cleaner and compressed air, with the base plate removed) set at 1-1/2 to 2 turns out from lightly bottomed with the primary ones, and about 1/2 turn out from lightly bottomed with the secondary screws. Start 'er up and give a go to adjusting idle mixture and rpm...

    Good luck with it. Let us know how you make out...
    Last edited by Walking-Tall; 07-30-2018 at 12:20 PM.
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

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