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‘63 Avanti —Hard starting issues

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  • Engine: ‘63 Avanti —Hard starting issues

    I continue to have difficulty starting my ‘63 Avanti. It still has the original Carter AFB. Rebuilt last year by Dave Thibeault. When I try to start the car cold I set the choke with a couple of pumps on the accelerator and crank it. It will not start. If I pour gas into the carb or a shot of starting fluid it starts on the first revolution. It stays running, so I’m pretty sure the fuel pump (also rebuilt by Dave) is OK.

    Dave says it’s obvious that the float bowl is empty and that I should pump it a couple of times, spin it over about 10 times, pump it a couple more times and it should start. It doesn’t. If I pump it about 20 times it might start. I have a buyer interested in the car and am reluctant to sell it with it acting this way.

    I have noticed that when I manually work the throttle that the accelerator pump only squirts gas for about 1/3 the length of the plunger travel. Shouldn’t the squirters be shooting gas out the whole travel of the plunger? Is there any adjustment for this? I have changed plungers and get the same result.

    I know the gas has changed over the years and it evaporates quickly and I’m sure Dave is correct about the fuel bowl, but if the fuel pump is delivering fuel to the carb, shouldn’t it be starting better than requiring 20 pumps on the pedal?

    I’m running non-ethanol premium with a little Avgas thrown in. I know someone will ask.

    Thanks. Tom

  • #2
    This is why people run electric fuel pumps. Find an impulse pump that your mechanical pump can draw through, and mount it on the frame near the tank. Power it through a momentary-contact switch that you can easily reach. Run the pump until the chattering slows down, before cranking.

    Once the car is warmed up, if you can hit the throttle and not have a momentary bog, then you should have enough accelerator pump shot.
    Gord Richmond, within Weasel range of the Alberta Badlands


    • #3
      Thanks Gord. I was hoping it wouldn’t come to that. I have an electric fuel pump for starting on both my ‘35 Commander and ‘37 Coupe-Express, so installing one on the Avanti shouldn’t be a big deal.

      I was going to save this question for another post, but now that you bring it up, I DO have a momentary bog when I hit it. With the 4-speed I have to be sure I get through that when taking off from a stop. What can I do about that?



      • #4
        Well, you may indeed have an inadequate accelerator pump shot. I think there are 2 or 3 holes on the plunger lever, and changing holes will affect both length and timing of the shot. Also perhaps the accelerator pump check valve might be letting some of the pump back into the bowl?

        And another common cause of "flat spot" is an inoperative vacuum advance unit.
        Gord Richmond, within Weasel range of the Alberta Badlands


        • #5
          I agree with Gord, the accelerator pump stroke IS adjustable, there are 3 Holes the Linkage can go in.
          Second Generation Stude Driver,
          Proud '54 Starliner Owner


          • #6
            Not carb related but a hard starting point. My '64 Avanti my Dad gave me started hard and I found that the incorrect starter was installed. It seemed that it wasn't cranking fast enough and sure enough upon pulling the starter it had an MDU from a regular V-8 instead of the MDY. I cleaned up an MDY as it should have and it made a huge difference in cranking speed and starting once installed . I also run premium ethanol-free gas.
            Rob in PA.


            • #7
              When the car sits for weeks or months at a time, the gas evaporates from the carb. The accelerator pump is leather so it dries out and is less effective or doesn't work at all. I would not replace unless it still has issues after having been driven a few times at frequent intervals to swell the leather again. What Dave T said is, of course, correct. A back up electric fuel pump wired through the acc. circuit and switched can be used to pump gas up to the carb. if the car has set for a few days. If Dave did your carb, don't mess with it. The accel pump gives you alittle shot of gas when you open the throttle abruptly. This prevents hesitation or stalling--too much gas could cause the engine to load up. It sounds like you don't really have a problem at all.


              • #8
                Thanks to all who have responded. Here’s a follow-up.

                I installed an electric pump along the frame just aft of the fuel drain plug and wired it to what is basically a starter button. The circuit is not energized unless I’m actually pushing the button. I learned my lesson with toggle switches the day I forgot to turn the fuel pump off and wound up with a lake of gas under my ‘35 Commander.

                I’ve cold started the car the last two mornings using the electric pump to prime and the car has started on the first or second engine revolution. What a difference! I know the gas has probably not all evaporated overnight, but I’m now much more confident that I can get in it any time and it will perform.

                I moved the rod controlling the accelerator pump to the hole closest to the carb. When I drove the seven miles to the closest store that pumps non-ethanol premium ( I had to drain the tank to install the fuel pump — I might as well use fresh gas in the Avanti and I’ll burn the drained gas in the lawn mower) I did not notice any bog after the car was warmed up and at speed. I pulled the accelerator pump check valve and as near as I can tell by sucking on it, it’s good

                Thanks again. Tom


                • #9
                  If you wire it to the accessory circuit, that can't happen and you will be able to pump gas up to the carb. with switch in the acc position. This avoids having the ign circuit on with the engine not running--a good way to burn the points. Just switch to acc and when the pump stops running you are ready to crank it over. Starts right up. Saves wear and tear on starters. I switch the electric pump 'cause I use it as a backup. If you use it as a primary pump you can still use the acc circuit but you might want one of those shut-off-the-pump-if-you-crash switches in the circuit (I think SI sells them..)