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Fuel cuts out

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by jon v, Aug 29, 2004.

  1. jon v

    jon v Registered Member

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    1979 Jimmy 350 465, 205. When I get going with hard acceleration, the engine cuts out, sputter sput sput, like I might be out of gas (full tank). I'm thinking gunk in the tank, or sock on pick up tube is bad, and the fuel hoses at tank need to be replaced. New Quadrajet, new fuel pump, tuned up. /forums/images/graemlins/thinking.gif /forums/images/graemlins/ears.gif Any helpful ideas would be appreciated. /forums/images/graemlins/k5.gif
     
  2. tx_sub

    tx_sub 1/2 ton status

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    eliminate the easy stuff first. filter? pump? check the lines. its an older rig, so the tank could be nasty. might be a good idea to have it cleaned and resealed. hard acceleration and no baffles in the tank could be starvation at the pickup. make sure the carb is jetted correctly. the secondaries may not be working properly. sorry, not much help. i haven't have a carb'd rig in 7 or so years.
     
  3. bajaviking

    bajaviking 1/2 ton status

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    I had the same problem and it turned out to be a fuel line that was bent so much that the it would not allow enough fuel to run through it when under full power. Just something to check for.
     
  4. 1-ton

    1-ton 1/2 ton status Premium Member

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    I would suspect an ignition problem because it is more common for an ignition problem to show up under acceleration than do fuel delivery problems. Fuel delivery problems tend to be more consistent and happen under all throttle loads.

    Now who is going to come in and Bitch Slap me, then tell me I do not know what I am talking about? Will it be Tim...maybe Blue85?
     
  5. jon v

    jon v Registered Member

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    Symptoms are like running out of gas; it jumps real hard. Has a new ignition module, plugs, wires, cap, rotor. Can cruise at 90 no sweat. What about vapor lock? /forums/images/graemlins/thinking.gif
     
  6. 1-ton

    1-ton 1/2 ton status Premium Member

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    [ QUOTE ]
    What about vapor lock?

    [/ QUOTE ]

    Vapor lock would most likely shut down your engine completely, and not just make it stumble. Have you ever replaced your ignition pick-up coil? Most people never do this because it is a somewhat complicated part to replace.
     
  7. TorkDSR

    TorkDSR 1/2 ton status

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    not to go against 1-ton.... but i had a similar problem.

    under load she'd sputter and die.

    i changed the filter and pump and my problem is gone. /forums/images/graemlins/cool.gif
     
  8. 1-ton

    1-ton 1/2 ton status Premium Member

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    If your engine pops or bangs a little (i.e. very light backfiring) when your engine has the problem you are talking about, then this would be a sign of an ignition problem, but if it only stumbles with no popping or banging, then this could indicate a fuel problem.
     
  9. jon v

    jon v Registered Member

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    Stumbles only, like running out of gas.
     
  10. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    [ QUOTE ]
    Now who is going to come in and Bitch Slap me, then tell me I do not know what I am talking about? Will it be Tim...maybe Blue85?

    [/ QUOTE ]

    How about Leadfoot /forums/images/graemlins/yikes.gif /forums/images/graemlins/screwy.gif /forums/images/graemlins/thinking.gif /forums/images/graemlins/whistling.gif

    J/K

    Question. I am having similar problems (actually almost identical). Ignition was ruled out though as vacuum advance was disabled on my HEI. The motor will rev 6500+ and not skip a beat in Neutral, but going down the highway it feels like it runs out of fuel at ~4200. I was told if it was the ignition (with vacuum advance disabled) that it would do it around a certain rpm, where fuel can vary due to the fact that fuel demand is different even at the same rpm due to load vs. no load.

    If that is the case it sounds like his problem is fuel and not ignition....

    Again I could be wrong, but this is coming from mechanics that I know as well.
     
  11. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    [ QUOTE ]
    1979 Jimmy 350 465, 205. When I get going with hard acceleration, the engine cuts out, sputter sput sput, like I might be out of gas (full tank). I'm thinking gunk in the tank, or sock on pick up tube is bad, and the fuel hoses at tank need to be replaced. New Quadrajet, new fuel pump, tuned up. /forums/images/graemlins/thinking.gif /forums/images/graemlins/ears.gif Any helpful ideas would be appreciated. /forums/images/graemlins/k5.gif

    [/ QUOTE ]


    I have been doing research, and it seems I either have a line that is sucking itself in or there is an issue somewhere in the secondaries or float in my Q-jet. I have swithed from mechanical to electric fuel pump. Replaced both filters, and even pulled the tank to check the "sock", and it still happens just the same as day 1. I even borrowed a known good HEI distributor and tried it with no improvements. If I ever get time to play with it and fix it, I will let you know what it was as it seems we have similar issues. If you figure it out, could you do the same.

    Thanx
     
  12. dyeager535

    dyeager535 1 ton status Premium Member

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    When it feels like its running our of gas, is it with the pedal to the floor?

    Regurgitating info, but when I put a new engine in my car, I took it out for a drive. (actually rebuilt the same engine from the vehicle, didn't change carb) If I accelerated WOT from a stop, right around 3000RPM, the vehicle would start to buck violently with the new engine. In neutral/park, no problems.

    Since I have a big selection, I went into my secondary metering rods, and found some that were a tad leaner. Swapped them out, and the problem was solved.

    Apparently the fuel pump was just borderline of not being able to supply enough fuel, or the restriction of the needle and seat, or the float is too low, something. But swapping the rods out fixed it, whatever the true cause was.

    As small as the rods actually are, I find it pretty hard to believe that the fuel pump couldn't supply enough, and a rod swap was enough to cure it, but obviously something was going on there, and I didn't feel like pulling the carb apart to find out.
     
  13. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    Yes, pedal is on the floorboard (or close to it). Back out of the throttle and everything is OK. Again only under load. I can rev it with no load and not skip a beat.
     
  14. dyeager535

    dyeager535 1 ton status Premium Member

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    Sounds like not enough fuel to me, but again, I've never seen a vehicle being starved of gas that didn't buck violently.
     
  15. jon v

    jon v Registered Member

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    Yep. Mine bucks violently, like running out of gas then getting gas with a load on it. From stop, accelerating to speed, or on freeway, especially up hill. Back off on pedal and it settles down.
     
  16. dyeager535

    dyeager535 1 ton status Premium Member

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    Got a spare set of secondary metering rods that are leaner? (fatter)

    Other "test", though not so precise and reversible, would be to increase the tension on the secondary air valve, and see if you can change the point at which it starts to act like it's starving of fuel.

    If running stock in-carb filter, I'd double check it's installation. I believe backwards they can restrict flow. Also need the spring underneath it.
     
  17. jon v

    jon v Registered Member

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    OK, think I fixed it. The rubber fuel line from the metal line at the frame, to the fuel pump, was cracked, and leaking fuel. Replaced it and now it runs like a champ. /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/k5.gif /forums/images/graemlins/thumb.gif /forums/images/graemlins/doah.gif /forums/images/graemlins/doah.gif /forums/images/graemlins/doah.gif
     

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