Hot start troubles - Pontiac GTO Forum
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post #1 of 5 (permalink) Old 06-10-2012, 08:02 PM Thread Starter
 
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Hot start troubles

My GTO starts right up when cold, idles and runs perfectly. When I try to restart when warm (5 minutes to an hour post shut down) it starts very hard and puffs fuel smoke. Cliff rebuilt it, and I sent it back to have him check it out again, but starts fine on his test engine. What else could cause this apparent flooding after shut down? Any suggestion is appreciated, this has been driving me crazy for a long time. Thanks
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post #2 of 5 (permalink) Old 06-11-2012, 10:11 AM
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What color is the smoke and are you sure it's fuel? Have a helper close by enough to get a whiff of it and see if it has a "sweet" anti-freeze type smell to it.

If so, it's coolant and you've got a leak somewhere, perhaps a head gasket or maybe something worse like a cracked head or block. That will cause a "hard start" because the liquid/vapor in the cylinder is trying to put it into hydraulic lock.

Also check your oil for any evidence of coolant. Coolant in the oil will cause it to take on sort of a "milkshake/rootbeer" type quailty.

I'm very familiar with this problem because I just went through it on my car. I had one head with a very small crack in an exhaust port that would open up and leak coolant into #6 during the transition while the engine was warming up.

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post #3 of 5 (permalink) Old 06-13-2012, 08:22 PM Thread Starter
 
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Originally Posted by BearGFR View Post
What color is the smoke and are you sure it's fuel? Have a helper close by enough to get a whiff of it and see if it has a "sweet" anti-freeze type smell to it.

If so, it's coolant and you've got a leak somewhere, perhaps a head gasket or maybe something worse like a cracked head or block. That will cause a "hard start" because the liquid/vapor in the cylinder is trying to put it into hydraulic lock.

Also check your oil for any evidence of coolant. Coolant in the oil will cause it to take on sort of a "milkshake/rootbeer" type quailty.

I'm very familiar with this problem because I just went through it on my car. I had one head with a very small crack in an exhaust port that would open up and leak coolant into #6 during the transition while the engine was warming up.

Bear
Thanks Bear. I am familiar with that coolant smell, sure it is fuel. And oil is clean, no foam. Athough I wouldnt have thought of that being the issue, but dont think it is.
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post #4 of 5 (permalink) Old 06-13-2012, 08:49 PM
 
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Have you checked the carb before trying to start the hot engine? If you're seeing any seepage or hearing any hissing or bubbling noises, the fuel could be boiling in the float bowl after you shut down. That could cause these kinds of issues.

Do you have the correct carb base gasket? Some of them are made of thick, insulating material to limit heat transfer from the manifold to the carb. Make sure yours is the correct one for your year/engine.

Is your fuel feed line (from the pump to the carb) routed correctly and not close to any hot engine or cooling system components?

If Cliff found the carb to be working properly, I'd check the fuel pump, too. It might be putting out too much pressure and overcoming the needle/seat shut-off. This should be evident all the time, though; it would be running rich and loading up all the time.

1968 Pontiac GTO
1983 Pontiac Bonneville (G) wagon
2008 Pontiac G8 base
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post #5 of 5 (permalink) Old 06-17-2012, 09:44 PM
 
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agreed, manifold heat is affecting fuel in carb.
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