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q-jet question

Discussion in 'The Garage' started by Justin Fleming, Sep 15, 2005.

  1. Justin Fleming

    Justin Fleming 1/2 ton status Premium Member

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    I have notice that if I go out and work on the carb before starting the truck that the seconday's wont open. Is this due to the choke linkages/mess??? Or is it possible that when I took all that apart and put it back together I messed something up??

    I just dont seem to be getting the performance that I would assume would be there when I jump on it. The exhaust is making alot of noise like air tryN to ruch out but the truck doesnt seem to make any power.

    If I go onto a dirt road from a dead stop it barely will brake the wheels loose. I know it is a stock 305 but I would assume a little more power would be there.

    I wonder if the cat is plugged up and also wonder about the cold start valve in the passengers exhasut. It is rusted in position. what the positio of the butter fly is unknown.

    New duals are going on it today :laugh: :laugh:
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    The secondary air valves open based on engine demand, and are held shut by engine vacuum. Meaning: in park/neutral the engine load is not sufficient enough to work the air valve setup.

    However, the secondary throttle plates (lower butterflies) are mechanically tied to the primary throttleshaft, so unless the choke is closed and they are "locked out" because of the choke, they will ALWAYS open when the throttle is stabbed.
     
  3. Justin Fleming

    Justin Fleming 1/2 ton status Premium Member

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    thanks for the great info. I think the situation is that the when I first work on it the choke is closed and it is not allowing me to manually open the secondary butterflys. The reason I noticed this is I went to set the TC cable yesterday and I could not get the throtle to go to full open position, hence the choke must have been holding it out

    thanks
     
  4. dyeager535

    dyeager535 1 ton status Premium Member

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    You say throttle, you mean the primary throttle shaft, or secondary throttle shaft?

    The primary throttle shaft is never restricted from WOT, so if it won't move to full open, something isn't right.
     
  5. Justin Fleming

    Justin Fleming 1/2 ton status Premium Member

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    primary works ok but the secondary does not open unless I release one of the choke arms. I assume that when the truck is warm it would be released on it own and should work correct. I will have to verify that.
     
  6. dyeager535

    dyeager535 1 ton status Premium Member

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    Yeah, thats correct then. If you look on the passenger side of the carb, right where the secondary throttle shaft passes through the base, you'll see the pin sticking out of the shaft, and the little "dogleg" piece that engages it when the choke is on.
     

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