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Surging...PLEASE HELP

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by rcpilot, Jun 2, 2003.

  1. rcpilot

    rcpilot 1/2 ton status

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    Started the truck on Sunday morn.. headed down the road and around 40 mph the truck started surging, /forums/images/graemlins/angryfire.gif kinda like running out of gas but a steady surge.. gets a little worse with more acceleration then bogs... I've checked the vacuum adv and its lines.. I tried different springs on the dist. advance weights..checked to ensure dist is tight..but to avail I'm at my wits end with this thing.. BTW its a '76 K-5 350/TH350/NP203.. running an Edelbrock mani and Edelbrock carb
    Thanks,
    Scott
     
  2. BRN78BLAZER

    BRN78BLAZER 1/2 ton status

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    OK, so as far as u know ignition is ok, probly not electrical being there is no obc, I would bet that its fuel/carb related. Basically check the filter and the pump, and if it only does this when its cold you may want to check the choke setting. Good luck

    Steve
     
  3. rcpilot

    rcpilot 1/2 ton status

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    I'll check the pump tomorrow to see what its output is... it surges whens its cold and hot... the choke is mech. and its not hooked up..
     
  4. pilgrim

    pilgrim 1/2 ton status

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    in doug roes book about Q-jets i'am reading, it has a graph that shows air/fuel ratio to economy... it states that when your mixture is bellow 16:1 (which is the best for "economy") you will get black smoke and sluggish performance. if your air/fuel is over that you will get surgeing-lean backfire-heavy bucking and over heating. of course the more to either extreme you are the worse those problems will be... so with that stated i would try rejetting your carb... maybe bring it by a shop with a chassis dyno so they can test your exhaust at WOT. /forums/images/graemlins/thumb.gif
     
  5. Confedneck

    Confedneck 3/4 ton status

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    stoichiometric a/f mixture ratio is 14.7:1.. which is perfect... wouldnt that be the best for performance? just wondering... trying to expand knowledge
     
  6. MousePowrd

    MousePowrd 1/2 ton status

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    Sounds fuel related, filter or pump I bet. Could be draining the float bowl under acceleration. Also check that the accelerator pump is putting a good squirt of fuel in when the throttle is opened
     
  7. pilgrim

    pilgrim 1/2 ton status

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    your right the ideal air/fuel is 14.7 to 1,which is best for performance, however the book states in this section that for ideal economy and emissions not performance the ratio should be 16 to 1. Why, hmmmmmm, lets see the book says that this burns up all the gas and leaves some air left. for "gasoline" 15 pounds of air to 1 pound of fuel is ideal. and since standard air presssure at sea level is 14.7psi, i suppose thats where we get the ideal air/fuel as 14.7/1. but as elevation increase's the air pressure drops and therefore you need to richen the mixer to compensate...

    Really this book is great and it has been recommended alot before on the site /forums/images/graemlins/thumb.gif... sure its all about rochesters and Q-jets but all carbs work on the same principles and this book does generalize...

    HP books... title- Rochester carburetors by Doug Roe...
    check amazon /forums/images/graemlins/thumb.gif
     
  8. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Fuel filter and if you don't have a fuel filter then it's trash in the carb. Could also be a bad fuel pump. Cracked diaphram in the pump will sometimes not leak fuel out but will suck air in and airate the fuel going into the bowl.
     
  9. BlazerGuy

    BlazerGuy 3/4 ton status

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    Could be the EGR valve, plug it up and see what happens... /forums/images/graemlins/deal.gif
     
  10. JustHorsinArownd

    JustHorsinArownd Registered Member

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    Believe what Doug has to say. He was the most amazing car guy I have ever met. Y'all should've seen his shop. The last time I was there right before he died he had a Maserati in there that they were paying him to make pass California emissions. hehe Maserati couldn't do it, he did. Just my two cents worth.
     
  11. rcpilot

    rcpilot 1/2 ton status

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    Thanks guys... yesterday I came home and the wife said the truck would'nt start.. check the carb and no fuel coming out the accel nozzles...checked fuel pump output and it was pathetic (sp)... so it's a new pump today..
    Again thanks for all the help /forums/images/graemlins/thumb.gif /forums/images/graemlins/thumb.gif
     

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