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adjusting fuel to air mixture on 3406c

Discussion in 'Trucks [ Eighteen Wheelers ]' started by jd2210, Jun 22, 2011.

  1. Jun 22, 2011 #1
    jd2210

    jd2210 Light Load Member

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    Oct 23, 2009
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    We have 2 3406c's in our fleet right now. One has 4:10's and can pull amazingly well and the other has 4:30's and gets passed by my small block mercedes. We know it isn't a turbo, or air to air or valve lash issue so right now I'm blaming my fuel to air mixture. I know of one adjustment screw on it but recently heard there are actually 2 you need to adjust to get the right mixture and lots of power. we need all the power we can get out of this truck since our weights are so high. Any help is appreciated.
     
    jd2210, Jun 22, 2011
    jd2210, Jun 22, 2011
    #1
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  3. Jun 23, 2011 #2
    Semi Crazy

    Semi Crazy Road Train Member

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    Middle Tennessee
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    The AFRC is only for limiting excessive smoke. It limits rack travel until manifold pressure catches up to fuel.

    Are the fittings on the line to the manifold tight?

    How much boost will it develop?

    Check the diaphragm in the AFRC. They do get hole in them. Same result as a loose line.

    If it smokes when fuel is applied quickly and then clears up as boost catches up it is adjusted good enough.

    For power you want to turn out the fuel (rack travel) and torque screws. That's different than the AFRC.
     
    Semi Crazy, Jun 23, 2011
    Semi Crazy, Jun 23, 2011
    #2
  4. Jun 23, 2011 #3
    AUSSIE DAVE

    AUSSIE DAVE Road Train Member

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    if you r going to adjust fuel, keep a very close eye on your pyro / EGT
     
    AUSSIE DAVE, Jun 23, 2011
    AUSSIE DAVE, Jun 23, 2011
    #3
  5. Jun 23, 2011 #4
    jd2210

    jd2210 Light Load Member

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    Oct 23, 2009
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    OK, Iassumed I was changing the AFRC, but maybe what I need is the torque screws you speak of. Where are they/it? I assume that is separate from the fuel (rack travel) since that is the one I'm sure we are already adjusting. Yes I've been warned to watch the Pyro. Yes we have already eliminated the diaphragm as being the problem.
     
    jd2210, Jun 23, 2011
    jd2210, Jun 23, 2011
    #4
  7. Jun 23, 2011 #5
    Superhauler

    Superhauler TEACHER OF MEN

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    keep stroking.
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    the fuel and torque screws are on the back of pump housing toward the bottom behind a little plate that has 2 bolts holding it on it takes aspecial tool to adjust them. that has a allen wrench through the middle of a socket. or if your real careful you can loosen the jam nuts and back out the screws. just dont forget to tighten the jam nuts when done.
     
    Superhauler, Jun 23, 2011
    Superhauler, Jun 23, 2011
    #5
    jd2210 Thanks this.
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