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No start condition when warmed up...Carb?

Discussion in 'The Hokey Ass Message Board' started by ChucksCrib, Sep 8, 2013.

  1. I have an edelbrock carb, 600 cfm, on a small block stroker. Truck starts right up when cold....truck also starts right up, when warmed up, should I get gas(or any other quick errand. However if the truck is warmed up, is then shut off and it sits for about 15 minutes or longer, it doesn't want to start. The engine turns over but it doesn't want to catch.

    Here is what I've done so far.......

    -rebuilt the carb
    -purchased an edelbrock fuel pump to get the pressure down to 5 psi(verified)
    -installed an insulating gasket which is about 5/16 thick. between carb and intake
    -7/16' float setting verified.
    -Checked all grounds

    I have to spray some ether into the carb to get it to eventually start but I do smell fuel when attempting to if to suggest it is flooded. burying my foot into the pedal upon restart doesn't help either.

  2. 61 chevy
    Joined: Apr 11, 2007
    Posts: 891

    61 chevy

    heat boilding gas out , carb gets too hot, put a wood spacer under carb, edelbrock is bad for that,
  3. So the 5/16" insulating gasket I currently have sitting between the carb and intake are useless?
  4. Apparently not quite useless, but not enough heat insulation.

    Try the phenolic spacer or you can make one out of wood.

    Run the thing up to temp, drive it home and let it set the same time to duplicate the problem condition. Take the top off the carb and see if there's fuel In there.
    If it was running fine 15 mins earlier the fuel bowl must have been full, but letting it sit hot and no fuel in the bowl - well where did it go ???
    It either leaked out or evaporated because the carb is too hot to keep the cheap gas from going off in heat induced vapors.

  5. 61 chevy
    Joined: Apr 11, 2007
    Posts: 891

    61 chevy

    sorry I cant say that, I used a 1/2 wood from JEGS,
  6. hoop98
    Joined: Jan 23, 2013
    Posts: 1,362

    from Texas

    The fuel will "percolate" with vapor formation, you might be able to watch it coming out in the venturi. As Vicki says, take the top off to verify empty float bowls so you are sure what problem you are chasing. If you have heat risers in the manifold you must be very careful that exhaust back-pressure is balanced. If there is a heat riser passage and one side has higher back pressure there will be constant flow under the manifold causing carb heat problems.
  7. Okay fine and fuel is evaporating in the bowls due to heat......wouldn't fresh gas get pumped back into the carb when I turn over the motor in 2 to 3 turns of the ignition?
  8. Standard gas&oil
    Joined: Dec 3, 2010
    Posts: 289

    Standard gas&oil
    from USA #1

    I would check fuel pressure and lower to 4.5 PSI. I had the same issue this summer and installed a regulator and fires right up every time after sitting hot. I thought a stock GM mechanical fuel pump would pump no more than 6 PSI but my gauge showed 8 PSI causing my Edelbrock to flood after hot shut off.
  9. gimpyshotrods
    Joined: May 20, 2009
    Posts: 18,468


    Did you check for spark when it is doing this?
  10. landseaandair
    Joined: Feb 23, 2009
    Posts: 4,473

    from phoenix

    I've got a Holley that does something similar and the thick Edelbrock insulating gasket didn't do anything to help either. SBC, single plane with no heat crossover. Starts fine initially and runs about 190. Shut it off and it heat soaks to 200 - 220 and you can hear the fuel boil. It will then spit enough fuel from the transition slots in the base plate to flood the engine, requiring it to be cranked wide open for a while to clear it out. Just installed a 1" phenolic spacer that seemed to fix it but only drove it once since. I also shimmed the back of the hood an inch to get some heat out (Chevy II with fenderwell headers).

    Sometimes wondered if the carb has issues but can't help thinking modern fuel formulas are to blame. Wouldn't be much of an issue in the average fuel injected car with a pressurized system.
  11. GassersGarage
    Joined: Jul 1, 2007
    Posts: 4,728


    In my case, with the Edelbrock carb, my fuel would boil and flood the engine. A space and fuel regulator cured that. My stock GM pump was putting out 8 lbs.
  12. Great replies thanks stated I already replaced the original fuel pump which was giving me 11 psi with the edelbrock fuel pump which brought me down to 5 psi and experience no change in does however, run much smoother. Looks like I'll try a 1" spacer. Summit/Jegs/speedway I presume?
  13. 40FORDPU
    Joined: Mar 15, 2009
    Posts: 3,122

    from Yelm, Wa
    1. Northwest HAMBers

    This, you are focusing on a fuel issue, when it may be ignition related.
    Conventional point type distributor, or HEI?
  14. His post says a shot of ether gets him started.
    But I'd still check spark anyway also.
  15. If the bowls are indeed empty, it can take quite a while to fill them again.
    Much more than 2-3 turns. 5-15 rounds of 2-3 turns is probably closer to what's needed.
  16. carbking
    Joined: Dec 20, 2008
    Posts: 3,118


  17. I read the post and keep thinking the motor is flooded. I would try holding wide open throttle and crank . See if engine will start?
  18. Merlin
    Joined: Apr 9, 2005
    Posts: 2,546

    from Inman, SC

    I had the same problem and a 1" phenolic spacer under the carb did the trick.
  19. blowby
    Joined: Dec 27, 2012
    Posts: 7,883

    from Nicasio Ca

    How did all those 70-80s cars hot start with carbs buried under crowded engine compartments bolted directly to low profile cast iron intakes? Better gas?
  20. J'st Wandering
    Joined: Jan 28, 2004
    Posts: 1,772

    J'st Wandering

    Correct, better gas.

    I would like to know what I could add to the gas that would lower the boiling point. I would think that that would solve the problem.

    I have the problem with quadrajet on a small block Chevy, an edelbrock on a Chrysler, and a Holley on a 300/6 Ford. All did the same thing. I put electronic ignition on the SBC and the problem went away. I figured the hotter spark worked through the flooded condition quicker. I have a 1/2 inch spacer on the edelbrock. It helped but still does it.

    I start the cars as though they are flooded. O.K. but more work for the starter and battery.

    Last edited: Sep 9, 2013
  21. Chuck when it is hot or warmed up as you say try looking down the throat of the carb to see what is going on. Is is drooling fuel all over the inside of the intake, that being the case it may be boiling the fuel out of the carb anfd flooding as has been suggested. if not then come back to us and let us conjecture some more about what it may or may not be doing?

    Before you throw more money at it diagnose what the problem is or isn't; become a mechanic and not a parts changer.
    Last edited: Sep 9, 2013
  22. shotrod
    Joined: May 14, 2005
    Posts: 90


    61 Chevy hit the nail on the head! It exactly what mine was doing I ended up putting a demoncarb on with the composite body and not a problem since.
  23. 34toddster
    Joined: Mar 28, 2006
    Posts: 1,482

    from Missouri

    To the OP, does it have points or is it electronic? If it has points make sure the wire from the + side of the coil is connected to the outside terminal of the starter.
  24. hoop98
    Joined: Jan 23, 2013
    Posts: 1,362

    from Texas

    If you want to make progress I think you need to start eliminating areas.

    You can check the fuel level in the carb, if it is empty then you can focus on that area, if not then move onto ignition. Guess is rarely productive and usually expensive.

    Hot ignition can be tested with an inexpensive ignition spark tester;

    KDT2757 For a standard ignition (15 KV)


    Once you know for sure which area we are failing in it is a much simpler job, so I suggest stop guessing, start eliminating.


  25. I kinda ruled that soon as I spray ether down the carb it fires right up.....might be coincidence.....but I'm thinkin' not
  26. I wonder if your electric choke has time to close but the engine is still hot ?
  27. The carb has no choke and I have an electronic dizzy. I like the idea of looking down the carb to see what happens after I shut her down
  28. Mojo
    Joined: Jul 23, 2002
    Posts: 1,862


    I think it's the gas. I think they're putting a whole lot more alcohol in it than they're admitting. The diaphragm in my 6 month old fuel pump disintegrated and i'm certain it's this "summer blend" gasoline.
  29. Good point I have been getting my gas from the same station.....I'll try another station

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