Carburetor question
08-01-2015, 11:16 PM
#1
Burning Brakes
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Carburetor question
Yesterday I took my '63 roadster out for the day. Made a few stops, and every time I got in it to leave she fired right up as usual. Then near the end of the last trip she seemed to hesitate or stumble under light acceleration. Went in store and came back out....she wouldn't fire up. I tried repeatedly and she turned over but wouldn't fire up. (Side note: it was hot here yesterday, but the car never overheated. She did this same thing one day last summer but fired up after cranking a little. Never seems to have any issues in normal temps outside).
Had a colleague swing by and pick up my son and I for a mtg. Went back about two hours later and I still couldn't get her to fire up. I took the air cleaner off and could see fuel dripping into the carb. Had my ten year old son with me, had him try to start it while I watched...and what do you know, he got it fired right up! I asked how he did that and he says he just kept the pedal all the way down. Crazy kid.
I had initially thought maybe there is a fuel delivery issue, but sounds more like she she may have just been flooded. Thoughts?
Oh I should point out that it has started just fine multiple times since that incident yesterday. I just don't know if I should worry or ????
Had a colleague swing by and pick up my son and I for a mtg. Went back about two hours later and I still couldn't get her to fire up. I took the air cleaner off and could see fuel dripping into the carb. Had my ten year old son with me, had him try to start it while I watched...and what do you know, he got it fired right up! I asked how he did that and he says he just kept the pedal all the way down. Crazy kid.
I had initially thought maybe there is a fuel delivery issue, but sounds more like she she may have just been flooded. Thoughts?
Oh I should point out that it has started just fine multiple times since that incident yesterday. I just don't know if I should worry or ????
08-02-2015, 02:48 AM
#2
Melting Slicks
Sounds like a classic case of percolation or a stuck float, which caused flooding. Your kid did exactly what's recommend for a flooding issue. 
Gary
Gary
08-02-2015, 06:47 AM
#3
Team Owner
Very common issue. One of those Harbor Freight I/R temp guns for about $25 or so will tell the story. Next time you have the issue shoot the carb bowls and if they're much above 145* or so that's percolation occurring. I think the fuel dribbling down the carb throat which you observed pretty much nails the problem already. It doesn't begin to occur until about 20-45 minutes after shutting the motor down after a long, hot run....engine heat then invades the carburetor and causes percolation.
The percolated fuel runs down and sits on the intake runners and then you are essentially starting a flooded car. Your boy got the startup technique correct for such a condition. Floor it until the car starts...
A second method (which is what I prefer) if you suspect you are going to have hot start problems is to keep your foot completely OFF the gas and crank the motor 3-5 seconds, stop cranking, then push the gas pedal SLOWLY 1/3 way down and then crank the car.....it'll fire up immediately....
I think the car just acts better directly after using method two...
If you confirm its percolation then do a search on here - lots of info on trying to reduce the problem (don't always work) and a couple of sure-fire methods: move to Alaska or fuel injection.
The percolated fuel runs down and sits on the intake runners and then you are essentially starting a flooded car. Your boy got the startup technique correct for such a condition. Floor it until the car starts...
A second method (which is what I prefer) if you suspect you are going to have hot start problems is to keep your foot completely OFF the gas and crank the motor 3-5 seconds, stop cranking, then push the gas pedal SLOWLY 1/3 way down and then crank the car.....it'll fire up immediately....
I think the car just acts better directly after using method two...
If you confirm its percolation then do a search on here - lots of info on trying to reduce the problem (don't always work) and a couple of sure-fire methods: move to Alaska or fuel injection.
Last edited by Frankie the Fink; 08-02-2015 at 07:44 AM.
08-02-2015, 08:08 AM
#4
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Went back about two hours later and I still couldn't get her to fire up. I took the air cleaner off and could see fuel dripping into the carb. Had my ten year old son with me, had him try to start it while I watched...and what do you know, he got it fired right up! I asked how he did that and he says he just kept the pedal all the way down. Crazy kid.
If the carburetor is still dribbling fuel two hours after you shut the engine off, it's not a percolation problem.
Last edited by MikeM; 08-02-2015 at 08:11 AM.
08-02-2015, 09:10 AM
#6
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Check your gas cap and see if it will vent to atmosphere.
08-02-2015, 10:27 AM
#7
Team Owner
I took the 2 hours with a grain of salt -- sometimes a stop can seem longer than it is.
Like when we used to visit the mother-in-law!
Like when we used to visit the mother-in-law!