Hard starting engine "warm"

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    Author Topic: Hard starting engine "warm"  (Read 6195 times)

    Offline brasil

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    Hard starting engine "warm"
    « on: May 15, 2015 - 04:49:24 PM »
    Hello folks...

    I am runnin my "new" Thermoquad fo a week now...  car runs like a dream   BUT when I want to start the car, after let´s say 20 minutes
    I have to crank the engine "some time "....

    With a cold engine...No Problems... just push the accelerator once...and with hin 2 sekonds the engine is running... same when the engine
    HOT  and I make letssay a stop at the gas station...to refill the tank...

    only when the car sits for 20 Minutes...or so...  the engine doesn´t want to start...so I have to crank theengine much longer.... and when she fires up...there is some black smoke commin out of the exhaust

    The AFR at Idle is 13.8   whlie cruising 14.5 -14. 9   WOT 11.3- 11.8   so these numbers look good

    Any ideas ??

    Thank you
    Greetings Juergen
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    Offline cudabob496

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    Re: Hard starting engine "warm"
    « Reply #1 on: May 15, 2015 - 05:16:41 PM »
    On a Holley 850 DP, I had that problem. Small holes in the throttle plates solved it.
    But also, you gotta make sure the rest of the carb is dialed in properly.
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    72 Cuda, owned 25 years. 496, with ported Stage VI heads, .625 in solid roller, 254/258 at .050, 3500 stall, 3.91 rear. 850 Holley DP, Reverse manual valve body.

    1999 Trans Am, LS1, heads, cam, headers, stall, etc! Love to surprise the rice rockets with this one. They seem so confident, then it's "what the heck just happened?"

    2011 Kawasaki Z1000

    Offline brasil

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    Re: Hard starting engine "warm"
    « Reply #2 on: May 15, 2015 - 05:22:19 PM »
    ...hmm  I don´t want to drill in the trottle blades...
    Could it be  "vapor lock " ??   the carb is dialed in ...  only the bowl vent ...is always closed.  Should I open the bowlvent...?

    Greetings Jurgen
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    Offline cudabob496

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    Re: Hard starting engine "warm"
    « Reply #3 on: May 15, 2015 - 05:51:30 PM »
    « Last Edit: May 15, 2015 - 05:59:43 PM by cudabob496 »
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    72 Cuda, owned 25 years. 496, with ported Stage VI heads, .625 in solid roller, 254/258 at .050, 3500 stall, 3.91 rear. 850 Holley DP, Reverse manual valve body.

    1999 Trans Am, LS1, heads, cam, headers, stall, etc! Love to surprise the rice rockets with this one. They seem so confident, then it's "what the heck just happened?"

    2011 Kawasaki Z1000

    Offline cudabob496

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    Re: Hard starting engine "warm"
    « Reply #4 on: May 15, 2015 - 06:02:15 PM »
    seems a lotta folks on the net are saying hot fuel perculating out of carb and flooding engine.
    Logged
    72 Cuda, owned 25 years. 496, with ported Stage VI heads, .625 in solid roller, 254/258 at .050, 3500 stall, 3.91 rear. 850 Holley DP, Reverse manual valve body.

    1999 Trans Am, LS1, heads, cam, headers, stall, etc! Love to surprise the rice rockets with this one. They seem so confident, then it's "what the heck just happened?"

    2011 Kawasaki Z1000

    Offline bs549

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    Re: Hard starting engine "warm"
    « Reply #5 on: May 15, 2015 - 06:41:53 PM »
    I had same problem....went with wood fiber spacer and cured my issue. .
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    Offline Bullitt-

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    Re: Hard starting engine "warm"
    « Reply #6 on: May 15, 2015 - 07:12:51 PM »
    Is it possible the choke is closing when it doesn't need it?
    Try not touching the accelerator pedal if you have been.
    « Last Edit: May 15, 2015 - 07:14:34 PM by Bullitt- »
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    Wade  73 Rallye 340..'77 Millennium Falcon...13 R/T Classic   Huntsville, AL
    Screwed by Photobucket!

    Offline brasil

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    Re: Hard starting engine "warm"
    « Reply #7 on: May 16, 2015 - 04:01:56 AM »
    ...  it´s the same...if I touch the acc pedal  or not...  perhaps the   floats a sitting a little to high ?  or this mysterious  HOT IDLE VALVE that this carb has... ?

    The wood spacer...??  I have a phenolic spacer between carb and intake.... about 1/4inch thick...

    the fuel bowl looks good...as far as I can tell...no fuel leakin...  also if the car sits for one two or even more days...  just one try and it runs...   no crankin nessesary.. So the fuel bowls shouldn´t leak...  right ?

    Greetings Juergen
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    Offline Bullitt-

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    Re: Hard starting engine "warm"
    « Reply #8 on: May 16, 2015 - 07:19:41 AM »
    I can't see the Hot Idle Valve being a problem, it opens to allow a small amount of air in to lean the mixture. 

    In my mind anything that effects warm start should be a problem with hot start.  :clueless:

    Only other thought..Is the car needing the choke to close at these temperatures to enriched the mixture?  ..
    « Last Edit: May 16, 2015 - 07:38:26 AM by Bullitt- »
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    Wade  73 Rallye 340..'77 Millennium Falcon...13 R/T Classic   Huntsville, AL
    Screwed by Photobucket!

    Offline dsburch

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    Re: Hard starting engine "warm"
    « Reply #9 on: May 16, 2015 - 10:49:37 AM »
    The "thermo" quad design was introduced to address exactly these issues.  It's supposed to manage heat better with that phenolic base to insulate, in effect reflect heat.  The spacer advice is probably the right track...  I use a 1/4" phenolic under a holley 750 and it really helps.   Also, try this - only open the throttle slightly for hot start without pumping or opennig the throttle up.  Just a slight pressure on the pedal for a second or two prior to hitting the key, and hold that position during the spin.  Works for me. 
    « Last Edit: May 16, 2015 - 10:52:21 AM by dsburch »
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    Offline brasil

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    Re: Hard starting engine "warm"
    « Reply #10 on: May 16, 2015 - 04:53:58 PM »
    Thank you all for your answers and advises
    I will check it all out   Also there is my fuel filter... he is made out of metall..I think I will switch over to a plastic filter....
    Next will be the float level... I think  1 "  will be the right hight... 

    Greetings Juergen
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    Offline cudabob496

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    Re: Hard starting engine "warm"
    « Reply #11 on: May 16, 2015 - 05:08:20 PM »
    Quote from: brasil on May 16, 2015 - 04:53:58 PM
    Thank you all for your answers and advises
    I will check it all out   Also there is my fuel filter... he is made out of metall..I think I will switch over to a plastic filter....
    Next will be the float level... I think  1 "  will be the right hight... 

    Greetings Juergen

    I put some pipe insulation around my metal fuel filter, and moved it
    so it would not see the hot air coming from the radiator.
    Also, these sheet metal shields are good. Just cut them and snugged them under
    the carb bowls.
    Logged
    72 Cuda, owned 25 years. 496, with ported Stage VI heads, .625 in solid roller, 254/258 at .050, 3500 stall, 3.91 rear. 850 Holley DP, Reverse manual valve body.

    1999 Trans Am, LS1, heads, cam, headers, stall, etc! Love to surprise the rice rockets with this one. They seem so confident, then it's "what the heck just happened?"

    2011 Kawasaki Z1000

    Offline Kapteenikosmos

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    Re: Hard starting engine "warm"
    « Reply #12 on: May 16, 2015 - 05:53:09 PM »
    I have three mopars with the same problem. I have identified the problem as gas "boiling" in the carb and flooding the engine. I can smell the fuel after maybe 15 minutes when the hot engine is shut down. Really annoying as I tend to run out of juice from the battery because of extensive cranking when visiting more than couple of shops for example. I have holley in Fury and Edelbrocks in Ramcharger and Challenger. Some have the spacer and some not. Must be the ****ty fuel we have nowadays.

    One intresting note though is that I used to have Edelbrock in my Fury which tends to have biggest issues with the boiling and I changed that into holley. It didn't cure the problem but it is marginally better now. That edelbrock went into my dad's Pontiac that has zero problems with the boiling. When hot, it always starts without even a need to touch the accelerator pedal. Zero hot flooding problems with that one. I have no idea why it is different.
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    Ville

    1967 six banger Mustang
    1973 Challenger (under restoration)
    1997 Lincoln Mark VIII LSC (daily driver)

    Offline cudabob496

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    Re: Hard starting engine "warm"
    « Reply #13 on: May 17, 2015 - 12:49:36 AM »
    A tightly sealed engine compartment, and non-vented hood, can make it really hot
    under the hood!
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    72 Cuda, owned 25 years. 496, with ported Stage VI heads, .625 in solid roller, 254/258 at .050, 3500 stall, 3.91 rear. 850 Holley DP, Reverse manual valve body.

    1999 Trans Am, LS1, heads, cam, headers, stall, etc! Love to surprise the rice rockets with this one. They seem so confident, then it's "what the heck just happened?"

    2011 Kawasaki Z1000

    Offline dodj

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    Re: Hard starting engine "warm"
    « Reply #14 on: May 17, 2015 - 10:04:26 AM »
    To see if It is boiling outof the carb, next time you park it after a drive, open the hood, remove the air cleaner, and look.
    On my engine i saw the throttle plates getting wet. And the symptoms you describe match my car's behavior. Though my new QF carb improved it a bit.
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    Scott
    1973 Challenger  440 4 spd 
    2007.5 3500 6.7 Cummins Diesel, Anarchy tuned.
    Good friends don't let friends do stupid things. ........alone.
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