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Old 08-16-2009, 09:46:17 AM   #1
gordonquixote
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Hard to Start When Hot.....Carb?

Usually I take the car for a spin and come home and park it for the day. Recently I have been driving the car on weekends for whatever is going on.

I've noticed that if I turn the car off after it is up to normal operating temperature (180*) and let it sit for a while.....I have to hold the gas pedal to the floor and crank the engine for about 4 seconds before it will fire up.....Then of course, when it fires the exhaust smells like gas until it burns off.

Carb or timing?

I have a 1000A battery, a CS130 alt, and a MSD6AL so I know I have plenty of spark. Carb is the Holley SA 770. Mechanical fuel pump.

FWIW, sometimes I notice that when the car is cold and has sat for a few days/weeks, the fuel filter is empty but several people have said that is normal.
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Old 08-16-2009, 10:31:56 AM   #2
Chevrolaine
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It won't start just pumping it 2 or 3 times?

I'd guess carb if you have to hold it to the floor all the time. I can't recall any carburated engine I've had to hold to the floor to start unless they were severely flooded.

Your not using one of those cheap see thru filters are you?!!
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Old 08-16-2009, 10:32:36 AM   #3
RothrockGuitar
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Sounds like fuel leaking from one of bowls into the intake, but that is usually a Q-jet habit.
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Old 08-16-2009, 10:47:14 AM   #4
Gary S
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Is your choke working right? It should stay wide open on a hot engine. If it doesn't, you will have hard starting and you will have to hold the pedal to the floor to clear the flooding.
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Old 08-16-2009, 04:00:00 PM   #5
kenny77
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Mine does something very similar. Let it set for less than like 10 min...restart fine. Let it set for 20-30 min does the exact thing as yours.

Let the car sit for an hour or so..no problem restart fine.

Have NEVER figured out why, in fact I've never spent so much time and effort on something and have not been able to fix it!
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Old 08-16-2009, 04:31:23 PM   #6
Gary S
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Quote:
Originally Posted by kenny77
Mine does something very similar. Let it set for less than like 10 min...restart fine. Let it set for 20-30 min does the exact thing as yours.

Let the car sit for an hour or so..no problem restart fine.

Have NEVER figured out why, in fact I've never spent so much time and effort on something and have not been able to fix it!

That sounds like your choke is either closing too fast, or too slow to give you the correct mixture for a quick start.
The choke is very easy to adjust.
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Old 08-16-2009, 05:06:16 PM   #7
kenny77
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No, no choke even hooked up. On my car choke is wired fully open all the time. It's like the engine/carb go into some kinda strange "heat soak" result is a flooded condition during that specific time in which you try to restart the car.

Last edited by kenny77 : 08-16-2009 at 05:15:01 PM.
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Old 08-16-2009, 06:23:30 PM   #8
Z28SSRS
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My 1978 does the exact same thing. A short stop, it starts fine. A long stop where it cools, it starts fine. An in between stop when it is hot, I usually have to hold the pedal down to get it to start, and even after starting if I am going slowly, like through a parking lot it might stall. I blame it on today's gas and heat soak like mentioned. Mine doesn't do this in cold or cooler weather, only hot.
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Old 08-16-2009, 07:08:34 PM   #9
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Just like others have said,I mainly believe it's how they refomulate the gas.From your fuel pump to the carburetor it seems it's evaporated and what's in your carburetor has evaporated too.
My Camaro does it all the time with temperatures above 90 and with the Corvette it starts ok but the idle is off about 100rpms until it runs a few minutes but I've got an air gap intake on the Corvette.
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Old 08-16-2009, 09:44:27 PM   #10
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It sounds like the carb leaking down into the intake.Like mentioned earlier in this thread. What kind of carb do you have?
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Old 08-17-2009, 12:16:32 AM   #11
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Quote:
Originally Posted by fast12
It sounds like the carb leaking down into the intake.Like mentioned earlier in this thread. What kind of carb do you have?

No way, I would have found that right away and carb is brand new 650 AVS. Did the same thing with my 670 street avenger.
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Old 08-18-2009, 01:50:38 AM   #12
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I have the same issue. I thought about insulating the fuel line so the fuel is cooler going into the carb. Maybe that might work?

I have a glass fuel filter and when the engine is hot, you touch the filter and it's reasonably warm, so when it sits in the bowl it gets hotter that much quicker. I don't know if that will solve the problem, but it's publicly embarrassing.
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Old 08-18-2009, 09:54:45 AM   #13
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Since heat seems to be the issue, how about one of these heat shields? Anyone using something like this?

http://www.summitracing.com/parts/HLY-108-70/
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Old 08-18-2009, 10:06:33 AM   #14
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Usually, it's heat soak that boils the fuel in the carb = hard starting when warm. The best cure for it is to insulate the carb from the intake. Usually that's accomplished by a thicker intake to carb gasket that has hard spacers where the studs pass through (spacers are thinner than the gasket material). Then there's the carb spacers that are either made from hardwood or a phenalic (sp?) which require a gasket between the carb & spacer along with a gasket between the spacer and carb.

Q-jets are prone to hard starting when warm because the welch plugs in the bottom of the main body of them get loose. The symptom of this is: cold start is normal. Hot start you have to hold the accelerator to the floor and you smell raw gas when it does start. Fuel mileage is crap. The fix is to rebuild the carb and when doing so either epoxy the welch plugs with an epoxy that is impervious to gasoline (like Hysol) or to put that funny looking block of rubber (that nobody knows what it is) in between the base & main body of the carb to in effect, seal the welch plugs. Here is a link to a picture of a complete gasket set where you'll see that funny looking gasket in the upper right hand corner: http://www.gesslerheadporting.com/members/gesslerheadporting/ghp.nsf/GHP-Q5150!OpenPage
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Last edited by Cardinal : 08-18-2009 at 10:10:03 AM.
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Old 08-18-2009, 10:19:08 AM   #15
gordonquixote
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Man - I can't put a spacer in between my carb/intake. I have about 3/8" between the air cleaner nut and the hood at this point.

I was hoping you guys would say turn a magic srew 1/2 turn out or something.

Or timing?
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