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Old 10-05-2011, 01:18 PM
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carb. leaking down

I have a 2bbl. rochester on my 283 eng. that seems to leak down gas overnight, and I have to pump alot to get started. Does the 2bbl. have plugs or plate on bottom that need epoxy, and will anything like epoxy stand up to gasoline? Thanks

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Old 10-05-2011, 01:31 PM
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Remove the throttle base of the carb and you`ll see the main wells.
Pour some gas in the carbs bowl and you`ll see where fuel will start dripping out of the main wells. Flip the carb over and drain the fuel out, leave it upside down for about 15 minutes to assure all the fuel is out of the bowl.
Find a punch with a square end, place it in the center of the main well and give it two medium licks with a hammer. Move to the next one and repeat the process. Next pour some more fuel back in the carbs bowl and watch for leaks. If there are none slap the carb back together and your on your way. If it still drips, give it a few more good raps with a hammer and punch. This is what I do to all my Quadrajets which are notorious for the main wells leaking. I tried the epoxy route a few times in the past and everytime it still leaked. That`s when I started restaking the main well plugs with a hammer and punch which has always cured the problem.
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Old 10-05-2011, 02:19 PM
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Have you seen the fuel leaking down the intake after shutting the engine off?
Or do you just assume it's leaking because you have to pump it so many times to start it cold? Reason I ask is it could just need an accelerator pump kit.
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Old 10-05-2011, 02:21 PM
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Quote:
Originally Posted by db flyer
I have a 2bbl. rochester on my 283 eng. that seems to leak down gas overnight, and I have to pump alot to get started. Does the 2bbl. have plugs or plate on bottom that need epoxy, and will anything like epoxy stand up to gasoline? Thanks
Is the opening of the carb round or sort of triangular? If it's a Rochester 2 Jet (2G, 2GC, etc.) it will have a round opening. Don't know if the wells will leak on these or not.

If it's a Dualjet it's basically the primary side of a Q-jet and these for sure can leak like DoubleVision talked about.
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Old 10-05-2011, 02:24 PM
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Quote:
Originally Posted by cobalt327
Is the opening of the carb round or sort of triangular? If it's a Rochester 2 Jet (2G, 2GC, etc.) it will have a round opening. Don't know if the wells will leak on these or not.
Exactly what I was thinking being it's on a 283.
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Old 10-06-2011, 08:19 AM
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This carb. is a rochester 2bbl. round hole 2G. I have put 2 kits in it including accelerator pumps. I have not seen any gas leaking down intake. This is a slow leak down. If it sets one day it will start with about 10 pedal pumps, if it sets 2 days then it takes 20 pumps. I am probably wrong, but I did not think there was lead plugs in bottom of the bowl on this 2bbl. like the qjet?
But I`ll take it apart and try anything. Thanks
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Old 10-06-2011, 08:42 AM
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Quote:
Originally Posted by db flyer
This carb. is a rochester 2bbl. round hole 2G. I have put 2 kits in it including accelerator pumps. I have not seen any gas leaking down intake. This is a slow leak down. If it sets one day it will start with about 10 pedal pumps, if it sets 2 days then it takes 20 pumps. I am probably wrong, but I did not think there was lead plugs in bottom of the bowl on this 2bbl. like the qjet?
But I`ll take it apart and try anything. Thanks
Are you sure this is not a choke issue.

Next time it sits for a day, before you start it open the choke and move the accelerator while looking into the venturi of the carburetor. See if you see gas shooting in. If you do it is not a leak down issue. If you don't then it is.
Lets try to identify the issue before attempting to fix it.
A leak down issue would most likely cause a longer crank time to refill the carb bowl, it would not necessarily cause you to pump the pedal more.
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Old 10-06-2011, 09:27 AM
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I have to pump and crank over engine both alot
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Old 10-06-2011, 09:29 AM
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Quote:
Originally Posted by db flyer
This carb. is a rochester 2bbl. round hole 2G. I have put 2 kits in it including accelerator pumps. I have not seen any gas leaking down intake. This is a slow leak down. If it sets one day it will start with about 10 pedal pumps, if it sets 2 days then it takes 20 pumps. I am probably wrong, but I did not think there was lead plugs in bottom of the bowl on this 2bbl. like the qjet?
But I`ll take it apart and try anything. Thanks
No lead plugs on this one. If a carb's worth of fuel were being leaked into the engine some how every time you drove it, the oil would be contaminated w/fuel. Have you smelled the motor oil to see if it has a gas odor?

The engine should start w/one or two pumps if the accelerator pump is OK (which it would seem to be, considering it works fine once the engine fires up, right?) and the accelerator well has fuel in it (as in, if the fuel hasn't been evaporated out of the carb due to heat soak or drained back past the needle/seat and fuel pump). But that it takes 10 pumps then a day later 20 pumps of the throttle to start it tells me that the carb is losing fuel to something at a pretty good rate, and by day 2 the carb is basically empty.

A weak fuel pump in general could cause a lag in fuel to the carb. If the fuel pump is allowing the fuel in the lines to drain back towards the tank, this could cause a lag between the time you start cranking to when the fuel reaches the bowl again. That, combined w/the fuel evaporating from the carb from heat soak or drain-back could combine to cause a long crank time. A fuel filter in the fuel line between the fuel pump and carb that allowed you to see the fuel in it would show you if the fuel was draining back past the fuel pump.

Bottom line is I suspect a bad fuel pump. No chance the gas cap isn't vented and the tank is pulling a vacuum, causing the fuel to be pulled back towards the tank? You might try opening the cap a bit to allow air in to see if this changes anything.
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Old 10-06-2011, 09:41 AM
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Thanks for your reply Cobalt. I must have a real odd problem, as I have changed to a new fuel pump and 2 new filters in the last 200 miles and 2 months. Yes I have looked at the oil and changed oil and filter 2 times in that 200 miles, and found no anomolies in oil, although I have not done a smell test. Also, I have tried a vented and also non vent caps, with no difference

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Old 10-06-2011, 09:45 AM
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Quote:
Originally Posted by db flyer
Thanks for your reply Cobalt. I must have a real odd problem, as I have changed to a new fuel pump and 2 new filters in the last 200 miles and 2 months. Yes I have looked at the oil and changed oil and filter 2 times in that 200 miles, and found no anomolies in oil, although I have not done a smell test.
Try loosening the gas cap. Did you look to see if the accelerator pump is squirting fuel after it sits for a day or two? Are you using an automatic choke? It gotsta be somethin'... !
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Old 10-06-2011, 09:57 AM
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Quote:
Originally Posted by cobalt327
Try loosening the gas cap. Did you look to see if the accelerator pump is squirting fuel after it sits for a day or two? Are you using an automatic choke? It gotsta be somethin'... !
Simple as a check ball missing in the accelerator pump reservoir.
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Old 10-06-2011, 10:13 AM
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Well, this situation is wierd. I just went out to car after setting for 2 days, and looked into carb. and saw that choke was working good and first pump of throttle showed a good squirt of gas, and then Ipumped it again seeing 2 more good squirts and started car with no problem. The temp. outside this AM is 38 degrees. This is first time I have started car with no problem. I have been starting the car in 80 degree + temps. when I see hard starting condition. The test this AM seems to show no leakdown?
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Old 10-06-2011, 10:16 AM
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I made sure check ball was in pump resevoir
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Old 10-06-2011, 11:34 AM
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Quote:
Originally Posted by db flyer
Well, this situation is wierd. I just went out to car after setting for 2 days, and looked into carb. and saw that choke was working good and first pump of throttle showed a good squirt of gas, and then Ipumped it again seeing 2 more good squirts and started car with no problem. The temp. outside this AM is 38 degrees. This is first time I have started car with no problem. I have been starting the car in 80 degree + temps. when I see hard starting condition. The test this AM seems to show no leakdown?
When you opened the choke to see the squirters were working, did this in any way change how much or little the choke flap was open OR how the fast idle cam was set?

I would try giving it two pumps, count slowly to ten, then start it. Who knows- you may have actually been flooding it!
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