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02-25-2014, 12:00 PM | #1 |
Junior Member
Join Date: Feb 2014
Posts: 3
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Gas leak from Zenith carb vent hole
I have a major leak at the air vent. When I take the carb apart - no apparent warp, good gasket. I can stop the flow of gas with the float valve with pressure from my finger. Float appears to be at correct 5/8" height.
Can't see the innerworkings of the float valve. Are the float valves originally equipped with a rubber tip to easily seal? My float valve "sounds" all metal. |
02-25-2014, 12:11 PM | #2 |
Senior Member
Join Date: Sep 2010
Location: michigan
Posts: 1,126
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Re: Gas leak from Zenith carb vent hole
did the problem happen all of a sudden
or is it a carb you got from some ware ? check the float valve and seat fuel shut off . |
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02-25-2014, 12:15 PM | #3 |
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Join Date: Apr 2013
Location: Northwest CT
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Re: Gas leak from Zenith carb vent hole
I had a pretty major carb leak over the summer. Turned out my problem was that the float valve had worked itself loose ever so slightly, I tightened it up and now it doesn't leak a drop (of gas). It might not be your problem but it's a quick and easy fix if it is. I'm pretty sure the original valves were not rubber tipped, there are aftermarket ones that do have a rubber coated seat.
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02-25-2014, 12:20 PM | #4 |
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Join Date: Apr 2011
Location: Glenmoore Pa
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Re: Gas leak from Zenith carb vent hole
The Viton tipped valves work better than standard depending on the manufacturer. Is the float valve you are using standard brass or a replacement? You "should" be able to get it apart to look.
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02-25-2014, 01:07 PM | #5 |
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Join Date: Feb 2014
Posts: 3
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Re: Gas leak from Zenith carb vent hole
I'm guessing mine is not a viton tip since it sounds all metal. Is there a best vendor for that kind of valve?
This is a resurrection project - '29 model A truck that hasn't run in 8 years. Fires up and runs now, I just can't get the carb to hold gas. |
02-25-2014, 01:10 PM | #6 |
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Location: Alabama
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Re: Gas leak from Zenith carb vent hole
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02-25-2014, 01:36 PM | #7 |
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Join Date: Jul 2010
Location: Cow Hampshire
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Re: Gas leak from Zenith carb vent hole
You can check the float by boiling water and then plunging the float under the surface.
The temperature heats the air within the float and the air comes out the leak and shows as a line of bubbles. Careful you don't burn yourself. Joe K
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02-25-2014, 01:45 PM | #8 |
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Location: michigan
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Re: Gas leak from Zenith carb vent hole
I don't know but great question
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02-25-2014, 05:26 PM | #9 |
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Join Date: May 2010
Location: Mpls, MN
Posts: 27,582
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Re: Gas leak from Zenith carb vent hole
About 5 years ago I had a speck of dirt get caught in the needle and seat, ao I turned off the gas valve and kept driving. As soon as the engine started to die I turned the gas back on. The inrush of fuel flushed out the dirt and it was fine the rest of the day.
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02-26-2014, 07:26 AM | #10 |
Member
Join Date: May 2010
Posts: 30
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Re: Gas leak from Zenith carb vent hole
What happened to lead you to think that a speck of dirt was on the valve needle? Did this happen while you were driving? Thanks in advance.
Ray in Illinois |
02-26-2014, 10:28 AM | #11 | |
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Join Date: May 2010
Location: Mpls, MN
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Re: Gas leak from Zenith carb vent hole
Quote:
Back in the 80's I was driving my diesel Rabbit and it started to miss on one cylinder. I figured a speck of dirt must be in the injector, so I figured the easiest thing to try to get it out would be to put a full load on the engine. There was a hill just ahead, so I drove slow to the hill then floored it all the way up the hill. At the top of the hill the engine was running fine again. This sure beat having to remove the injector and taking it apart. |
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02-26-2014, 10:39 AM | #12 |
Senior Member
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Re: Gas leak from Zenith carb vent hole
Like Purdy says it has to one of those problems as this is the vent for the bowl and the only way for fuel to leak out there is if the bowl is over full from one of the reasons above.
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02-26-2014, 12:00 PM | #13 |
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Join Date: Nov 2013
Location: Ahwatukee, AZ
Posts: 115
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Re: Gas leak from Zenith carb vent hole
Mine did the same (leaked through the drain) turned out that the needle valve was sticking open because the float was too wide for the housing and got jammed in the housing. A little careful bending fixed it.
Ned
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Retired civil engineer. Winters in Phoenix, summers in Ipswich, Mass. and North Dakota. '29 closed cab pickup- Excellent AZ truck. '29 roadster- Owned for 21 years but now sold. '28 CC pickup- My first car in Andover, MA back in '62- '63. |
02-26-2014, 12:51 PM | #14 |
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Join Date: May 2010
Location: Windy City
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Re: Gas leak from Zenith carb vent hole
I'll stick with a burnished and properly seated steel pin/brass seat valve. Fine rust particles cannot imbed as with softer polymer needle seats. Both Tom W and I have posted in the past about fixing original style steel pin valves. They reliably seal drip-tight and do not stick or glue themselves to the seat if left for extended time.
I don't like the grosse-jet type either. On rare occasion they can get their balls in a knot. When they do work (99.9+% of the time) their steel-to-brass seat is as drip tight as a steel pin valve and they do not suffer rust particle embedment like polymer tip valves. Viton as a bag of worms. A DuPont trademark, they define 8 grade categories, with multiple formulations in each. Only two, grades "F" and "GFLT" are rated for low fuel permeation (swell resistance) and use with alcohol blend fuels. Many 'Viton' valves fail because they are made with cheaper, wrong, or knock-off fluoroelastomer blends from other manufacturers. If it is an OEM needle from a current (alcohol blend fuel era) carburetor manufacturer the right stuff is used. ANY other aftermarket supplied 'Viton' needle is a crap-shoot. |
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