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Thread: Need Help with Weber dcoe 40 on 3tc

  1. #1
    Join Date
    Apr 2016
    Location
    Nanaimo BC
    Posts
    14

    Need Help with Weber dcoe 40 on 3tc

    Hey guys. I have a stock 3tc with header and a single Weber 40. I'm brand new to carburetors and need some guidance.

    I got this carb and intake of a buddy. He tells me it came off a running 3tc, and ran fine. I put it on my 3t with the existing factory fuel pump/filter. I ran a clear line from the pump to the carb when I first got it running. It ran ok but had lots of air bubbles in the line, so I figured the pump must be worn out. I was going to eventually upgrade to an electric pump anyway, so I got a small rotary pump with a fuel pressure regulator and plumbed it all in with an aftermarket inline filter.

    The car will start, but runs like absolute crap, and fuel drips out the end of the horns and bottom of the carb. I messed with the reg to try and make it work, the gauge wouldn't even read and it would leak out. So I checked the float and it's not stuck.

    Fed up, I got a factory replacement fuel pump. Put it all back together, retaining the aftermarket filter, and noticed the new pump came with a return. I Plumed in the return line to where it would go off the factory carb. I've read that the factory pump is pre regulated to 3.5 psi, so I tried to start it, and it ran even worst, and even more fuel

    What am I doing wrong??

    Thanks in advance


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  2. #2
    Join Date
    Apr 2016
    Location
    Nanaimo BC
    Posts
    14



    Sent from my iPhone using Tapatalk

  3. #3
    Join Date
    Apr 2013
    Location
    Victoria BC
    Posts
    977
    I always shoot for the low end on fuel pressure for DCOEs... make sure you are actually at 2 or 3psi max...

    It sounds like the needle isn't sealing against the seat -- or the float level is too high... The proper way to judge the float height is to check the ACTUAL fuel level in the bowls... not by some measurement of the float when it's apart... Fuel level is hyper important to DCOE tuning... Hyper.

    Have you checked that the needle seals against the seat? If there's a piece of crap stuck there or the needle is shot it'll flood.

    If you really want the carb to be perfect, beg or borrow a wide band O2 sensor and weld in an exhaust bung. It totally eliminates guess work. That carb is tuneable like a musical instrument... Don't give up. If it stumbles or has a non-linear power band, it's not right. It can be perfect. The Webers on my car run 12.7 - 13.25 AFR under all power conditions.

    You may find some info in here that is useful (don't miss the bit about fuel level -- but with Weber E-tubes, your level will be lower...): http://www.dorikaze.net/showthread.p...highlight=dcoe
    Last edited by b-rock; 07-17-2016 at 10:19 PM.
    $28 Bronze T50 shifter bushings HERE

  4. #4
    Join Date
    Apr 2013
    Location
    Victoria BC
    Posts
    977
    This all may sound like a different language, but if you read about how DCOEs actually work, the mystery will vanish. The common Weber books are good... One by Pat Braden...

    Honestly, if you don't learn or aren't into fiddling a bit, they can be frustrating... and get terrible fuel economy. Once you learn and tune them.... the fiddling STOPS basically forever. It's not rocket surgery. It's just info.
    Last edited by b-rock; 07-17-2016 at 10:30 PM.
    $28 Bronze T50 shifter bushings HERE

  5. #5
    Join Date
    Feb 2007
    Location
    calgary ab
    Posts
    414
    Open up the carb and look at the float. old brass ones can leak, allow fuel into the float and make it heavy. thus making impossible for needle to seat and control fuel level.
    new ones have plastic floats. they can break off near the pivot and also be usless.
    in general the new plastic ones are better. old carbs can be fitted with new plastic floats.

    Gary

  6. #6
    Join Date
    Apr 2016
    Location
    Nanaimo BC
    Posts
    14
    Thanks for the info guys. I looked at the float last night, it is an old brass one, but it still floats. I'll take a look at the needle tonight


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