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Posted this in "The Garage..." "Bog on acceleration..."

Discussion in '1969-1972 K5 Blazer | Truck | Suburban' started by Topdown, Jan 19, 2003.

  1. Topdown

    Topdown 1/2 ton status

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    Posted this in \"The Garage...\" \"Bog on acceleration...\"

    Anyone have any thoughts on what might cause the bog on acceleration? Edelbrock carb, edelbrock intake (air gap), New dist, New cap, New rotor, new plugs, new wires... short of a complete rebuild I dont know what else to do. Its not timing because I have gone in 2 degree incements (roughly) across the whole curve and have gotten nowhere. I dont know much (nothing) about carbs, but could this be the accelerator pump? I seem to recall others having this problem too but I dont know if they solved it or how.

    Anyone got any idea's?

    Thanks
    -Ryan /forums/images/graemlins/k5.gif
     
  2. ntaj*ep

    ntaj*ep 1/2 ton status

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    Re: Posted this in \"The Garage...\" \"Bog on acceleration...\"

    It could be the accelerator pump or even the mixture settings, do you have an adj. vac. advance?
     
  3. Steve_Chin

    Steve_Chin 1/2 ton status

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    Re: Posted this in \"The Garage...\" \"Bog on acceleration...\"

    If it's a true bog, something is over-rich. If it's a bog that happens only when yu hit the pedal, then smootens out after the initial hit, the accelerator pump is at fault. If it takes a long time to clear out (or it doesn't clear out until you get back into a cruise type throttle position), the enrichment circuit is at fault.

    If the thing is hesitating and/or parakeet sneezes through the carburetor, it's lean. If it only happens when you hit the throttle and clears up, then your accelerator pump isn't giving a big enough shot. If it surges or backfires under throttle, the enrichment circuit is too lean.
     
  4. Topdown

    Topdown 1/2 ton status

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    Re: Posted this in \"The Garage...\" \"Bog on acceleration...\"

    Hmm... I am thinking accelerator pump. The carb is about 6 months old... so nothing should be wrong... As for vac. adv. I have no vac. adv. I am running only centrifugal... I tried a bunch of different setting with the vacuum and finally just removed it to see if that would help. It hasnt. The problem is such: I will sit at a light and idle... green light, accelerate normally and it coughs, bogs, almost dies then picks up and runs like a striped ape. If I am cruising and try to slowly accelerate, it does something similar only to a lesser degree. Per the tailpipe, its running just about right as far as mixture goes. A nice chocolate brown-ish color on the end of the pipes.

    Thanks guys!

    -Ryan /forums/images/graemlins/k5.gif
     
  5. Steve_Chin

    Steve_Chin 1/2 ton status

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    Re: Posted this in \"The Garage...\" \"Bog on acceleration...\"

    Sounds like your camming is bigger than the carburetor was set up for. You need to re-jet the carburetor so that the primary enrichment circuit puts a little more fuel into the mixture when vacuum is low. Also, you will probably need to mess with the secondary circuit once you get the primary circuit ironed out.
     
  6. Dieselmh

    Dieselmh 1/2 ton status

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    Re: Posted this in \"The Garage...\" \"Bog on acceleration...\"

    I know this may be a little too elementary, but have you changed your fuel filter? I've seen dirty filters cause all kinds of wierd problems, one of which is bogging under acceleration.
     
  7. Topdown

    Topdown 1/2 ton status

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    Re: Posted this in \"The Garage...\" \"Bog on acceleration...\"

    not elementary at all. I have actually changed: Fuel filter (both in-line and carb), cap, rotor, distributor, intake, carb, and a few other things. I seem to have gotten rid of it for the most part, I believe it to have been the accelerator pump. Though it still has a small bog...

    -Ryan /forums/images/graemlins/k5.gif
     
  8. ZZ4x4

    ZZ4x4 1/2 ton status

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    Re: Posted this in \"The Garage...\" \"Bog on acceleration...\"

    Just wanted to throw one other thing in... I had a major bog too. I went through 3 carbs (q-jet, edel 1407, and holley truck avenger). I tuned each one, changing springs, adjusting secondaries, idle, mixture etc.. per the instructions and could not get rid of the bog. I finally got smart and decided it had to be something else. Went out and bought a fuel pressure gauge and found 13 PSI fuel pressure /forums/images/graemlins/shocked.gif. Needs to be 5-6 PSI. Turns out the new fuel pump I had installed last year was a racing pump labled as a street pump. After installing a fuel pressure regulator, the bog vanished. Seems like Greg72 also had a similar problem with fuel pressure and q-jets last year. Just a thought.
    JT
     
  9. Topdown

    Topdown 1/2 ton status

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    Re: Posted this in \"The Garage...\" \"Bog on acceleration...\"

    good to know... I will have to check that. my bog almost disappeared when I moved my accelerator pump arm... but not completely. its still there and still irritating me to no end. I have all but given up of resolving it as I am about to have an engine built with all new parts (no old engine scavenging) so if it shows up in the new one I am going to go ballistic. /forums/images/graemlins/eek.gif

    -Ryan /forums/images/graemlins/k5.gif
     
  10. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    Re: Posted this in \"The Garage...\" \"Bog on acceleration...\"

    Ryan,

    It could be two things (from my own hard learned experience)

    1. Excessive Fuel pressure (a mechanical pump going bad)
    2. Lack of full advance with the timing.


    I had a fuel pump that would occasionally push around 19 psi...not easy to trace, but I eventually found it and replaced the pump and put a regulator to insure no more than 6 psi from now on.

    Also, when I started swapping in my new MSD billet distributor, the springs were too "heavy" and I couldn't get more than around 25* total advance....talk about a "dog"!!! The lighter springs allow me to get 34* now, and the engine is MUCH snappier.

    Anyways....two ideas that might help.


    BTW -> If you crimp your own plug wires, be sure to check the resisitance of EACH one....I had a 6000 ohm wire that wasn't helping me out much either! /forums/images/graemlins/grin.gif
     
  11. Topdown

    Topdown 1/2 ton status

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    Re: Posted this in \"The Garage...\" \"Bog on acceleration...\"

    Thanks! I think the fuel pressure regulator is a good idea. I will put it on the list of things to add with the new engine install. As I will also be getting a new distributor I will have to check the weights/springs and make sure about it also. Thanks for the advice!!

    -Ryan /forums/images/graemlins/k5.gif
     

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