Engine dies when I step on the gas

Slant 6 Engines

  1. rivertaff

    rivertaff Member

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    I'm thinking my accelerator pump has gone bad in my 67' dart. Few days ago I was driving it home, I barely pressed the gas and it stumbled and died. I've been driving the car pretty much everyday since then with no observable issues. The carb is a 1920 that the previous owner replaced fairly recently now (1-2 years old) The car still idles fine but as soon as I press the pedal the slightest in park, drive, or neutral that's when it gives up. Any thoughts?
     
  2. Ricks70Duster340

    Ricks70Duster340 Child of the King, widower FABO Gold Member

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    Could be the accelerator pump, but could also be a clogged fuel filter. When the engine is off, look into the throat of the carb and move the throttle open. Do you see a strong shot of fuel? If not, the carb should probably be rebuilt. How long has it been since the fuel filter has been replaced?
     
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    • rivertaff

      rivertaff Member

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      I tried this yesterday, It appears to give a good shot of fuel. I had replaced the fuel filter when I got it with one of those cleanable aluminum edelbrock filters, but I'm gonna take it apart today and take a look when I get home. Hopefully it's something as basic as the filter.
       
    • Lefty71

      Lefty71 Well-Known Member

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      If its just the accelerator pump, you would still be able to rev the engine up and maintain speed, as long as you open the throttle slowly. If it falls off no matter what, then you have a clog or lack of fuel pressure somewhere along the line, whether it be at the tank end, fuel pump, or filter, or maybe needle and seat stuck.
       
    • krazykuda

      krazykuda Well-Known Member FABO Gold Member How-To Section Editor

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      If it dies when you step on the gas, don't step on the gas....
       
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      • pishta

        pishta I know I'm right....

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        The pump in those is kinda weird. It may have a weep hole that will piss fuel onto the exhaust manifold if the seal goes bad when the pump is relaxed. Easy to replace. Whats your timing set at?
         
      • DrillNFill

        DrillNFill Active Member

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        I was having this exact same problem this week. I started the Dart ('70 Swinger w/ 225/auto) Saturday morning for the first time in ~ 2 weeks and it started/ idled as usual for about 3-4 minutes, then I gave it some gas and it stumbled and died. It did that about 5-6 times over the next 5 minutes while I was trying to drive, then it stopped dying after that ( I drove it for another 15 minutes without a problem). I started it this morning after it sat for 3 days, I let it warm up about 5 minutes, and it stalled once about 50 feet from my driveway, then no more while I drove it 20 minutes to work.

        For what its worth, it was ~ 40*F out both mornings here. Any ideas or advice? Im not sure its the fuel filter since it stops stalling after ~5-10 minutes. And it never did it before this week, but I've only had the car since September-put a whopping 60 miles on it since then!
         
      • Bewy

        Bewy Well-Known Member

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        Post #7. Might be the choke hanging up or not operating correctly.
         
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        • GFlo

          GFlo Active Member

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          This happened to me as well, shortly after I got my '71 Valiant last summer. Turns out the Holley 1920 had a small crack near the accelerator pump. When you stepped on it, it would leak gas out the carb onto the intake manifold! With the gas not going into the engine, it obviously leaned out and wanted to die. So I got a Carter BBS and rebuilt it with good quality parts. Runs great now!
           
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          • AJ/FormS

            AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

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            Here are some possibilities; start at the top, and work down

            1) closed bowl-vent
            2) stale gas; all the VOCs have evaporated, and the thick-chit won't light off. On a hot day, or after the engine is up to temp and shut off; the gas in the vented bowl will be stale in just hours.
            3) low fuel level in the bowl
            4) varnished slow-jet or passages
            5) throttle is too far closed and the Transfers cannot respond fast enough
            6) Cold intake manifold
            7) loss of timing with loss of vacuum, or failure of the advance system
            8) lazy accelerator pump.
            9) bad coil.

            Notice I put the A-pump near the bottom. This is because from idle to off-idle, as you described it, that pump is NOT the main player. The main players on a clean carb,are;
            1) the freshness of the fuel
            2) the fuel level, and
            3) the transfer slots willingness to respond.
            4) the entire fuel/air charge ALL making it into the cylinder, not puddling in the plenum or sticking to the cold runners.

            Notice I didn't mention the power-valve/ metering rods either. They don't come on line until much later.

            Happy Hot-Rodding

            BTW, if the fuel is fresh, and the fuel level is correct, then it will run for a very long time; perhaps more than a minute, at idle; edit; with the fuel line disconnected or pinched. I forgot that part,lol.
             
            Last edited: Apr 29, 2021
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            • DrillNFill

              DrillNFill Active Member

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              Thanks all, the car isnt at my house so I cant check it right away, but I will. This is my first carburated auto so Im by no means an expert at diagnosing carb issues. Like I said, it seems to idle fine but when it died it was the instant I tapped the accelerator (and only while in "Drive"). It is old fuel and fuel filter which will be changed shortly ( the gas in the tank is at least from September when I bought the car)

              FWIW, I think its probably running a little too rich, I noticed black soot on the floor by the tailpipe where I left it to idle for ~5 minutes. Not sure if that narrows it down (at all).

              Thanks everyone!
               
            • Bewy

              Bewy Well-Known Member

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              Yes, what I said in post #8.
               
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              • DrillNFill

                DrillNFill Active Member

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                I feel you may be right the more I think about it. The stalling I described could mean the choke may be stuck in the open position, correct?
                 
              • Brooks James

                Brooks James Dustoff

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                Buddy with a boat twin engines had the exact problem . Water condensation inside distributor cap, once it warmed up to full temp it as ok.
                 
              • Bewy

                Bewy Well-Known Member

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                If the stalling occurs once the engine is warm, most likely the choke is still closed or [ partially closed ]. At operating temp, choke blade should be vertical & not able to flop around.

                If this happens with cold engine, then choke may not be closing fully.
                 
              • DrillNFill

                DrillNFill Active Member

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                A little update- was finally able to take it for a cruise on Saturday. Checked the carb choke before I started the car- it was fully closed. Checked it again after letting it idle about 5 minutes, the choke was fully open. Seems to be working as it should, and the car didn't stall once during the 20 minute drive. Guess I'll let it warm up a little bit before I drive and keep an eye on it for now.
                 
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