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Old 05-06-2021, 01:06 PM   #1
EDavid
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Default Zenith "B" Carb Leak

This is my first post. Never had issues before. I have a 31 Sedan with a Zenith "B". The car is not new to me I've owned it more than 50 years.
Starts great, idles great, runs great.
After running the carb dry it stays that way for about a day then I start to get a fuel drip from the GAV needle (aka Fuel Adjusting Needle).

I'm stumped. Why is it doing this? Help greatly appreciated.
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Old 05-06-2021, 02:16 PM   #2
henry's 31
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Default Re: Zenith "B" Carb Leak

Hi David:

It sounds like your shut off valve might be leaking. If your valve is close and you disconnect the line in the carburetor and it still drips then the shut off valve is defective. I am changing mine this weekend. Hope this helps.
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Old 05-06-2021, 04:19 PM   #3
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Default Re: Zenith "B" Carb Leak

I agree with Henry, your fuel shut-off is leaking. But with that said your carb should not leak because the shut-off is bad.

Chances are you have dirt under the float needle valve that is causing a secondary drip.

Take the carb apart and clean it and you might be good for the next 50 years.

Drain the tank and install a new shutoff and make sure you have a pencil filter installed.
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Old 05-07-2021, 08:42 AM   #4
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Default Re: Zenith "B" Carb Leak

1. i ALSO VOTE FOR Dirt from gas tank ... Pencil filter in shutoff valve will stop dirt from getting into carb and shutoff valve.

Dirt in valve will damage it making it hard to turn and make it leak.

2. My experience is that if you have Ethanol gas which is more that 3 to 6 months old it turns to "goo" and makes float valves leak and plugs up carb jets and etc.

This problem is worse in humid weather.

Last edited by Benson; 05-07-2021 at 08:51 AM.
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Old 05-07-2021, 11:34 PM   #5
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Default Re: Zenith "B" Carb Leak

The '31 coupe I am currently doing some maintenance on has a leaky carb. on it after the engine ran the carb. dry with fuel petcock shut off. I removed the shut off valve to rebuild it. Found out it is a reproduction valve so my rebuild kit won't work on it. Could blow air through the valve with it closed from my lung power. Took the valve apart to find a little bit of debris in the valve, cleaned that out and reassembled. Tested again it is fixed. Need to give the carb. a little attention next. Installed the parts using Permatex aeronautical grade sealant, the old teflon tape had disintegrated and left behind a mess.
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Old 05-25-2021, 12:03 PM   #6
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Default Re: Zenith "B" Carb Leak

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Here's where I'm at.
Replaced gas tank valve with new. That solved half the problem. Valve closed and no gas runs through to carb. However, when open I still get fuel leakage out of the GAV on the carb. Will now move to plan "B" to see if I've got something in the carb itself causing the problem.
All these years never had this issue.
I'm open to any other ideas/suggestions anyone may have.
Thanks folks.
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Old 05-25-2021, 12:26 PM   #7
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Default Re: Zenith "B" Carb Leak

Quote:
Originally Posted by EDavid View Post
Here's where I'm at.
Replaced gas tank valve with new. That solved half the problem. Valve closed and no gas runs through to carb. However, when open I still get fuel leakage out of the GAV on the carb. Will now move to plan "B" to see if I've got something in the carb itself causing the problem.
All these years never had this issue.
I'm open to any other ideas/suggestions anyone may have.
Thanks folks.
If this is a new problem, and you have not messed about with the carb, I'm with the others and would look first to the float valve staying open. Don't at this point go "fixing" the rest of the jets or valves, work on one thing at a time. When you do open the carb if you see a bunch of crap in the float bowl that will be your clue that some dirt or rust has gotten into the system. If you see that I'd pull the sediment bowl and clean out/replace everything on the gas delivery system up to and including the float valve (when you replace the float valve, go ahead and spring for the more expensive "viton" seal float valve). Once the new float valve is in there are a couple of ways to set the level.

  • Turn the upper part of the carburetor upside down. The seam on the float bowl should be parallel to and 1" from the ground gasket surface of the upper half of the carb.
or
  • In use, the fuel level should be 5/8" below the same surface. You can measure this with a little gizmo that replaces the drain plug, the gizmo is available from the Model A vendors.

Also - check to see that your float is not leaking. After removing it from the upper half of the carb, shake it to see if you hear liquid inside. You should also immerse it in hot (just shy of boiling) water to see if you see bubbles escaping. Either of these conditions indicates a leaking float, and it should be replaced.

Hope these give you some direction.

If you are a member of MAFCA, there's an interesting article in this month's Restorer magazine about Zenith carburetor leaks.

Good luck. In case you haven't figured this out by reading these posts, leaking carburetors are a popular topic.

JayJay
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Old 06-15-2021, 02:58 PM   #8
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Default Re: Zenith "B" Carb Leak

My thanks to everyone. Leak problem solved. Broke down carb and cleaned all jets. Everything fine now. Thanks again.
This by the way is my first car. 1964 I wanted a hot rod dad talked me into buying this car. Paid $450.00 and it ran but what a mess. We restored over the years. I drove this car all through college. I was the hit of the fraternity. Can't bear to part with it. Do have some other issues have to correct before it goes to my son's family.
My tail lights only work when the cowl lights or the high beam lights are on.
suggestions anyone? Check all wiring all connections seem sound.
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Old 06-15-2021, 06:47 PM   #9
JayJay
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Default Re: Zenith "B" Carb Leak

Quote:
Originally Posted by EDavid View Post
My thanks to everyone. Leak problem solved. Broke down carb and cleaned all jets. Everything fine now. Thanks again.
This by the way is my first car. 1964 I wanted a hot rod dad talked me into buying this car. Paid $450.00 and it ran but what a mess. We restored over the years. I drove this car all through college. I was the hit of the fraternity. Can't bear to part with it. Do have some other issues have to correct before it goes to my son's family.
My tail lights only work when the cowl lights or the high beam lights are on.
suggestions anyone? Check all wiring all connections seem sound.
The fact that your taillights work with cowl lights and high beam, but not low beam, doesn't cry out to me to be a problem with wiring or the lights themselves. More likely with the switch.

Down at the bottom of the steering column is the can that attaches the wiring harness to the bottom of the steering column. If you open that can you'll find the wiring harness connected to a flat plate with a bunch of copper contacts. As you rotate the light switch the contacts in the can (that engage the spider on the light switch rod) contact various of the copper contacts on the contact plate. I'd look to both sides of that connection - the contact plate on the harness and the contacts in the can - to be sure that all the contacts are corrosion-free, clean and grease-free.

On the back (wire side) of the flat contact plate in the wiring harness the wires connect to the terminals that go through the contact plate. Make sure they are all still solidly connected.

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Old 06-16-2021, 03:15 PM   #10
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Default Re: Zenith "B" Carb Leak

Harness I checked but not the rod. After all these years you'd think I'd remember the little things. Thanks for the tip.
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Old 07-01-2021, 10:38 AM   #11
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Default Re: Zenith "B" Carb Leak

Thank you Jay. All is well. All is working. Car runs like a top as they say.
Regards to to you. E. David
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