Bad cough - over-fueling affect gears?
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500, 472, 425, 368 Discussion, Bad cough - over-fueling affect gears? in Cadillac Engine Technical Discussion; Hi, i have a 1970 eldo with 500 engine and 4mv carb, the carbs been previously overhauled and ive had ...
  1. #1
    Captain wow's Avatar
    Captain wow is offline Cadillac Owners Member
    Automobile(s): 1970 Eldorado (prev:78Eldo-73Eldo-79CDV-78Sev-79Sev)
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    Question Bad cough - over-fueling affect gears?

    Hi, i have a 1970 eldo with 500 engine and 4mv carb, the carbs been previously overhauled and ive had it apart and as far as i can tell its all good and correctly set up. I have put a new "edelbrock 1994" power piston spring in (the original was missing- at the mo its got the gold one in..?) its also got a electric carter 6psi fuel pump located at the rear next to the tank (the mechanical pump was missing and blanked off when i got it).

    So my issue is this: today i took it the shops and back, slow and steady and it ran perfect..but! sometimes it decides to cough and choke, could be at the lights around town and it was doing it loads on the motorway when decelerating,. On the motorway it was quite scary as it would cruise great at 70-80 mph but dropping any slower would cause it to cough and also to jolt and surge as if the gears couldnt decide which to choose. Then when i pull over at the gas station it would cut out as if choking on too much fuel.. the only way to clear it is to start it back up and rev hard and after a big cough of black smoke everything would be ticketty boo for a bit.. so my guess is it was choking on too much fuel at the lower speeds and the black cloud cough is it gettiing rid of it.

    The carter fuel pump apparently self regulates. so i dont know if there would be any need for a regulator. I checked the float etc and that is all free and seats niceley.
    If the car is coughing and stumbling would that cause the gears to shift up and down at 65-70 mph? I think it was the gears changing...i dont have a tach so cant be 100 percent sure.
    Also could the fuel pump be overpowering the float needle system and forcing it open?
    I need to double check the fuel filters on the carb and in line, and im gonna do a serious vac leak search.

    Ive also recently gained a fair amount of oil in the aircleaner pan.

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    cadillac_al is offline Cadillac Owners Connoisseur
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    Re: Bad cough - over-fueling affect gears?

    Quote Originally Posted by Captain wow View Post
    Also could the fuel pump be overpowering the float needle system and forcing it open?

    Ive also recently gained a fair amount of oil in the aircleaner pan.
    That was my first guess.

    That oil could be blow by; not healthy

  4. #3
    Captain wow's Avatar
    Captain wow is offline Cadillac Owners Member
    Automobile(s): 1970 Eldorado (prev:78Eldo-73Eldo-79CDV-78Sev-79Sev)
    Join Date
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    Thread Starter
    So if the fuel pump is intermittently for ing it open is that the pumps internal regulator fault? It's pretty noisy and I do hear it change pitch which I'd presumed was the pressure changing. Unfortunatly there's not much info on the pump aside from "it doesent need a regulator.

  5. #4
    Captain wow's Avatar
    Captain wow is offline Cadillac Owners Member
    Automobile(s): 1970 Eldorado (prev:78Eldo-73Eldo-79CDV-78Sev-79Sev)
    Join Date
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    Location
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    Thread Starter

    Re: Bad cough - over-fueling affect gears?

    Hi, Update:
    im soaking the caranckase breather as a friend suggested a clog could cause the oil in the air pan?-if not then why would it pull in excessive oil here?
    gonna clean out the fuel filters...also try it with out the carbs paper filter.
    wondering if i need a regulator as the carter pump i have is rated at 6psi internally regulated.
    Ordered Doug Roes book on quadrajets..should be interesting.
    Gonna pull apart the carb again and note all the numbers: i have a feeling the rods and seats have been messed with.
    Anyone out there know exact settings for a 4mv on a early 1970 eldo 500 ? i have rebiuld tech notes but i wondered if you guys have more tried and tested suggestions for my old beast with electric pump.?
    ALso anyone have thoughts on gear changes afeected by over fueling??

    happy belated halloween btw!

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