Motor dies when gas pedal pressed

Discussion in 'Fuel and Air Systems' started by dICKj, Sep 27, 2018.

  1. dICKj

    dICKj Member

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    OK, this is a 318 2bbl 1974 Duster that I just bought. It is hard to start and wants to stumble and stall right off idle. I can't even touch the accelerator until it is well warmed up. I have to use a spray of starter fluid to start it. I temporarily wiredd the choke open to be able to run it. The previous owner put a brand new carb (2bbl) on it. Once it warms up, if I ease it through the flat spot when running in neutral, the engine will finaly rev up fine, but it is real difficult to get it to 2,000 where it will take any throttle to speak of. It's almsot like there is no accelerator pump in this carburetor. I'm starting to think there is dirt in the carb, what do you guys think? Fuel pump? Blocked fuel line?
    DickJ
     
  2. TrailBeast

    TrailBeast Slightly Twisted Member

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    Just off the top I would check for accelerator pump shot in case they are plugged up, then take that carb off and do a disassemble and clean on it.
    Just so you know, a crappy ignition tune can act about the same way, but the carb would be a good start after a quick ignition system checkover and timing setting check.

    Putting your hand over the carb about 50% of the opening and a quick tip in of the throttle can tell you if it's a lack of fuel causing it, because it will make that flat spot go away by causing more vacuum with your hand which makes the carb supply more fuel. (quick, easy and cheap diagnostics):D
     
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    • diymirage

      diymirage HP@idle > hondaHP@redline FABO Gold Member

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      Sounds like a transmission problem



      Ok, it doesn't, but the point is, consolidate your post, and give us as much info as possible

      Check your timing first

      Then check fuel flow
       
    • tonysrt

      tonysrt FABO Gold Member FABO Gold Member

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      1st is the choke problem, should be closed when cold and have vacumn canister to assist in opening choke when running. If carb is new shouldn't be the problem. 2nd would be timing, it has does have the original mopar electronic ignition? that would eliminate points. If retarded timing, would buck and shudder and just run bad. Timing should be about 10 degrees advanced at idle and about 34 at 2000 RPM if you have timing tape on Crankshaft balancer. Could also be checked with timing light with a readout of total advance. Of course it also depends on the inards of the engine if all is well. My 318 when it ran bad had all bent push rods and a bad distributor. You just have to check everything methodically. Also if choke is electric make sure you have 12 volts at the connection.
       
    • VolksDuster

      VolksDuster Back Yard Guy

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      I had a pretty much the same issue. :BangHead:
      And on that problem I got a lot of good feed back from a lot of guys here.
      If anything the best advise I got for a good running carb was the original with a rebuild kit and a good cleaning. However it is always good to check your plugs because they can give you a lot of info, also I was told when doing a spark test, use a good 3/4'' gap and be sure it's blue. As for the Ignition system, like distributer, coil, resister, and ECM it's not likely but coil and resister would be my aim if so. And because you say it can be heated up then it start's and idles on it's own I assume the engine isn't rough at this point. So I would have to say is a carb issue. I went through a lot of frustration over this with a remand carb that just didn't seem to want to work, even after a rebuild to it. Initially when the carb was purchased it was the wrong one (tagged incorrectly), it was a smog carb which was hard to tell because after a tune it started and idled great. But RPM'S dropped just a bit more than usual when put in gear and when you tried to accelerate it would die out unless you worked the throttle. When exchanged for the correct carb it was the same issue, on top of them having the same issue for some reason I had to adjust the arm that controls the pump. It wasn't allowing enough fuel because it wasn't high enough for proper travel and pressure. Which may be you issue and would be easy to see and gauge just by taking you breather off. And after that finally I got the original out as suggested then rebuild that and it has been great ever since. As for the choke, the rod should have a fair amount of pressure holding the choke closed to the correct setting. Also take it off and check the coil inside the choke for rust and an excessively soft spring action, they are cheap and are basically needed for a cold start unless you want to pump more fuel in with your foot.
      After all that blah blah blah
      I would say first check your external carb settings before even starting the engine.
      Then check plugs to narrow out any specific cylinders and check for excessive oil, carbon bad burning, etc.
      Then check the spark strength at each cylinder.
      If all are ok the check the timing when warmed up (anything between 5-10 degrees is good for checking things out).
      And if everything is okay up to this point... It's is your carb. Probably the leather on the accelerator pump not being flared and soaked properly, maybe a missing check ball, or even bad movement in the needles
      Find a good condition original you and can rebuild it or if needed by a rebuild kit for yours being sure it's the correct carb.
      Oh, FYI. After all that, here I am switching to 4bbl :D
       
      Last edited: Sep 27, 2018
    • Tooljunkie

      Tooljunkie King of cobble/master of the broken bolt FABO Gold Member

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      I would start with spark plugs.
      Acc pump may need adjusting.
      A “new” carb may or may not be the end all to the problem.
      I put a rebuilt on my 318 and it never ran so bad. I ended up overhauling my original and it took some work to get it where i was happy with it.
      You need a manual to get it dialed in,accellerator pump, choke and power valve all have specific settings that need to be very close.
      It may be just dirt/residue clogging the jets and could be fixed easily with a right proper cleaning.
       
    • 70aarcuda

      70aarcuda Master Hoader of SBM FABO Gold Member

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      no accelerator pump shot...can not prime engine to start.....no accelerator pump shot engine bogs ....

      get a flash light and look down into the carb as you move the carb throttle...it should squirt gas as soon as it is moved...
       
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      • Abodybomber

        Abodybomber Breaking street machines , since 1983.....:)

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        The proper way ,Greg...
         
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        • Abodybomber

          Abodybomber Breaking street machines , since 1983.....:)

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          Factory rebuild carbs ,SUCK !
           
        • 1Fast340

          1Fast340 Well-Known Member

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          This is where to start with this problem.
           
        • dICKj

          dICKj Member

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          OK. I looked down in the carb and no squirt. I disconnected the fuel line at carb and turned over engine with starter -really weak spirt. Will change fuel filter and blow out fuel line next and try again. Thanks for help, I will keep progress posted.
           
        • dICKj

          dICKj Member

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        • RustyRatRod

          RustyRatRod Just another dumbass. Technical Editor

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          Sounds like the choke circuit and the accelerator pump circuit both are not working properly. The carburetor needs work.