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1949 2r5 six choking out when pushing gas pedal (169.9 ci)

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  • Engine: 1949 2r5 six choking out when pushing gas pedal (169.9 ci)

    Need some advice here, I have rebuilt the carburetor, engine idles fine, when stepping on gas pedal, engine chocks out, have attempted to adjust air fuel mixture, but still have same problem. truck can be driven and shifted threw to 3rd gear, but has no power as when I step on the gas pedal the motor almost chocks out but does not accelerate.

    Could this be a distributor malfunction? could it be a bad diaphragm in the rebuild carburetor? any and all help will be appreciated.

  • #2
    So, you can build up speed if you press the gas pedal s-l-0-w-l-y ?

    With the engine off I'd look down the carb throat and open the throttle. A stream of gas should squirt out instantly.
    If not, perhaps one of the accelerator pump check valve balls is misplaced..


    • #3
      There is no "Diaphragm" but the accelerator pump may not be soft and plyable to seal, or the stroke of it is not adjusted properly.

      How OLD are the rebuild parts and how long ago was it "Rebuilt"?

      Fuel Pump putting out OK, pull the line and look.

      I think you may talking about "Choking". Speaking of that, what setting do you have the Manual Choke at? In cold Temp. at warm-up, you need it almost closed at startup, and less as it warms.

      If you have a Car Carb. with Automatic Choke, that needs proper cold adjustment also.
      Last edited by StudeRich; 12-27-2014, 02:30 PM.
      Second Generation Stude Driver,
      Proud '54 Starliner Owner


      • #4
        carb was just completely rebuilt by Studebaker international. I have also replaced fuel pump with new rebuilt. manual chock is half open when idling, if fulling open or closed, engine does not idle.


        • #5
          slowly is correct


          • #6
            First off, look for a vacuum leak. Is the carb securely attached to the manifold, with a good gasket? Is the vacuum line to the distributor intact and connected to the port on the base of the carb? Is the line to the vacuum wipers (where used) intact, and connected to a motor that isn't leaking (disconnect and cap the line to test).

            A distributor malfunction will generally result in the engine missing and running rough at all times, not solely under acceleration. A smooth loss of power, accompanied by a "gasping" sound, is characteristic of fuel starvation. You are hearing the normal intake suction sound of the carb without the normal roar from the exhaust to balance it out.

            With the engine off, remove the air cleaner, and look straight down the the throat of the carb, with the choke open. Work the throttle. You should see a strong jet of liquid fuel spurt out of a little nozzle on one side of the passage each time the throttle is opened quickly. Not a dribble, but a squirt, like WD40 coming out of the straw on the spray can. If that squirt is not there, or is only a dribble, then the accelerator pump in the carb is your culprit. It may be a "fresh" rebuild, but how long did it sit on the shelf before it was installed. Or there may be a little debris blocking the jet or one of the check valves.

            One type of distributor malfunction that can cause a "flat spot" on acceleration is a bad vacuum advance unit (but the flat spot is not usually as severe as you describe). To check it, remove the distributor cap so that you can see any motion in the breaker plate, then disconnect the vacuum line to the carb, and using a suitable length of tubing, apply vacuum by mouth to the advance unit. If the unit is good, it will feel like you are sucking on a closed pipe, and the breaker plate will move on its pivot, about 1/8" at the point where the link from the advance unit attaches. If the diaphragm in the advance unit is bad, you will be able to draw air through the line easily, and see no movement.

            I would look to it being a carb-related problem first, though.

            One last thought: if you have, or can obtain a vacuum gauge, hook it up the manifold and get a reading with the engine idling, and again when you try to rev it up. Could tell you a lot.
            Gord Richmond, within Weasel range of the Alberta Badlands


            • #7
              I was reading about this Carter carb in my old Motor's Shop Manual last night. They said if the vent isn't adjusted correctly it can make the engine run rough during acceleration. The vent should just be open when the choke is open and throttle is at idle. As soon as the throttle is opened the vent should be closed, or it can admit too much air into the main jet.

              I need to learn how to post pictures, but the vent is under the cover held on by 1 screw on my 1950 Champion. I'm not sure if your carb has the same dust cover over the linkage on top of the bowl.


              • #8
                Gord's advice is spot on...
                I had a '49 2R10 that had a horrible warpage between the intake ports and the exhaust ports.
                Had bad vacuum leaks.
                Machined the manifold (to block) mating surfaces and the engine smoothed out and ran like a little watch....
                Easy enough to check.
                Take the manifold loose and put a straight edge on the gasket surfaces.
                They all should be even, and not high/low/high/low....
                HTIH (Hope The Info Helps)


                Get your facts first, and then you can distort them as much as you please. Mark Twain

                Note: SDC# 070190 (and earlier...)


                • #9
                  Thanks for all the recommendations, I have not had time to do the suggested troubleshooting yet due to a travel schedule, but I'm encouraged by all of your knowledge, thanks so much for the advice.


                  • #10
                    another way to check for leaks is with by spraying a little (I forgot what) around the intake manifold and at the base of the carb while it's running....
                    Listen for the engine to speed up or slow down. That's where your leak is.


                    • #11
                      A clean, quick and easy way to locate vaccum leaks is by using an unlit propane torch. Just open the valve a little and move it around the intake. The engine should run better when you hit the leaking area.