tearing my hair out..... | FerrariChat

tearing my hair out.....

Discussion in '206/246' started by yakxx21, Sep 25, 2014.

This site may earn a commission from merchant affiliate links, including eBay, Amazon, Skimlinks, and others.

  1. yakxx21

    yakxx21 Karting

    Jun 29, 2013
    230
    #1 yakxx21, Sep 25, 2014
    My 246 ..has heads just rebuilt...compressions all good...plugs good timing marks spot on..BUT seems to be only running on 5 and a half cylinders...and when I short out plugs one at a time I find that number 4 does not change tone at all....ie its not pulling its weight.
    the other clue is that when I adjust the low mixture screw...I can get all of them to respond ( about 1.75 is good it seems) except carb nearest cylinder number 4 ...I can screw it all in or out and it does little...carbs were rebuilt ...but only a clean up job.....
    any ideas anybody ....??
     
  2. Nuvolari

    Nuvolari F1 Veteran
    Owner Silver Subscribed

    Sep 3, 2002
    6,419
    Toronto / SoCal
    Full Name:
    Rob C.
    #2 Nuvolari, Sep 25, 2014
    The very first thing I would check is the idle jet for the #4 cylinder. If it is plugged then the idle mixture screw would get no fuel and it would explain why it is not responsive to changes. Remove the jet, blow it out with air and put it up to the light to see if it is blocked at all.

    Outside of that you will want to remove the top of the carb, check the float heights and look for dirt in the float bowls that could cause a jet to clog.

    Lastly with the carb off use a straight edge to make sure that the base of the carb is perfectly flat. A warped base could cause an air leak and therefore a running problem. Carbs are not a black art or require any magic. ANY problem can be traced back to a mechanical fault so it is important to find what part of the chain is broken.
     
  3. abstamaria

    abstamaria F1 Rookie

    Feb 11, 2006
    2,668
    Full Name:
    Andres
    #3 abstamaria, Sep 25, 2014
    Good advice, Rob, which I will note too. Many thanks.

    Andy
     
  4. dgt

    dgt Formula 3
    Owner Silver Subscribed

    Jan 14, 2011
    1,283
    Northeast, USA & Oz
    Full Name:
    Andrew
    #4 dgt, Sep 25, 2014
    Does the bad cylinder have any vacuum hoses to it that are not connected or leaking and just bypassing the carby?
     
  5. tbakowsky

    tbakowsky F1 World Champ
    Consultant Professional Ferrari Technician

    Sep 18, 2002
    19,387
    The Cold North
    Full Name:
    Tom
    #5 tbakowsky, Sep 25, 2014
    Do a running compression test. Take the shader valve out of the adaptor, and start the car. Compare the readings to a known good cylinder. The reading will be lower then a static test when running, so will will need a constant to compare the readings.
     
  6. Cessna150dip

    Cessna150dip Rookie

    Jan 12, 2014
    3
    #6 Cessna150dip, Oct 8, 2014
    Why take out the shader valve ??? Tried that but it just jumps all over the place ....I mean oscillates with each compression at a high frequency ????
     

Share This Page