340 engine - hard to start after it's been sitting for awhile.

Discussion in 'Carter' started by Ohighway, Jul 18, 2010.

  1. Ohighway

    Ohighway Well-Known Member

    67 Skylark , 340 engine with Carter AFB 4-barrel. The car seems to run ok, and will re-start easily after it's been run earlier in the day. However if I let it sit overnight and try to start it.... it just cranks and cranks and cranks....

    Give it a shot of starting fluid and it'll start and run. I noticed when it's hard to start I get no fuel "shot" into the carb. My questions, is the hard starting problem due to issues with:

    1) Internal fuel leakage inside the carb?

    2) A worn accelerator pump ?

    3) A weak or flaky fuel pump ?

    4) Some other potential issue ?

    Any and all responses appreciated.
     
  2. SpecialWagon65

    SpecialWagon65 Ted Nagel

    Accelerator pump, and check integrity of fuel lines-
    I had a metal line worn and it dripped just enough
    to make it hard to start. Found it when I put an electric pump on and it sprayed like crazy out the hole!
    Check Rubber lines too.
     
  3. Ohighway

    Ohighway Well-Known Member

    Any hints on a good source for a carb rebuild kit for this one ?
     
  4. scott kerns

    scott kerns Silver Level contributor

    Look into the carb and pull on the linkage controlling the accelerator pump.
    Do you see a good stream of gas? If no it is the accelerator pump.

    If your concern was the fuel pump it wouldn't idle well after warming up as it wouldn't be getting enough gas.

    A quick search found a rebuild kit from summit and this one

    http://www.carburetion.com/_inv/invtocartpic.asp?Part1=KT-5281

    I believe topcat had a thermoquad for sale that was rebuilt not to long ago.

    Good luck.

    Scott
     
  5. TODD'S 67

    TODD'S 67 Time for another Buick!

    I always had to pump it 2 or 3 times when cold to get her goin. Sometimes it would die then 1 more pump and it would start and stay running. Weird!
     
  6. Ohighway

    Ohighway Well-Known Member

    To answer a question, when It's hard to start I get NO stream of gas when I blip the throttle. However I was having a hard time thinking it was the accelerator pump because when it IS running, there's no "stumble" when I blip the throttle. (In my experience that stumble usually happens with a bad/worn accelerator pump.) Kinda made me think maybe the fuel pump wasn't really pumping enough gas until the engine got up a little speed (like when I give it the shot of starting fluid) I just don't know.

    Thanks for the tip on the carb RB kit. I'll probably do that just for general principles. Ditto a new fuel filter for the carb.
     
  7. gsjohnny1

    gsjohnny1 Well-Known Member

    notorious carb for back leakage. put in a electric fuel pump.
     
  8. BroadbentA

    BroadbentA Well-Known Member

    Not sure if the 4BBL carb has a power valve but the 340 I had with the 2BBL carb was hard starting after sitting overnight and I traced it to a faulty power valve (which emptied the float bowl when the car sat overnight). My solution was to plug off the power valve with a brass plug which completely did away with the power valve and solved the problem altogether. Once the float bowl is empty it does take time for the manual fuel pump to refill the carb so the car will start. If it isn't a power valve then some other portion of the carburetor is dripping fuel into the manifold when the car is sitting - this would also account for crappy fuel economy as well since raw gas continually drips into the intake while the motor is running. An in-line electric fuel pump would cure the long cranking sessions in the AM but the real cure would be a carburetor rebuild by a competent mechanic.
     
  9. robert caris

    robert caris Well-Known Member

    check your rubber line at the fuel tank, make sure it is good and not sucking air. I had that problem on one my cars.
     

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