Need a carb guru from planet Zenith!

[Maclab58]

My late 31 Victoria has a Zenith 2 and it leaks gas out of the air intake like crazy even with the GAV turned all the way off. When driving anytime you let off the gas you can hear it popping back thru the manifold. Where do I start?

[msmaron]

Make sure all the bolts are real snug. Clean out all the jets and the filter screens to check for rust and debris. Clean out with forced air the jets. Check the float level. Start there and make sure you have new gaskets.

[Tom Wesenberg]

You should drain the gas from the tank and fix the tank valve first, before you loose all your gas or have a fire.
Then take the carb apart and see if you have a bad float, or junk in the needle and seat, etc.

If the tank valve isn't too bad you should be able to lap it with toothpaste or fine grinding compound. I did mine over 10 years ago and it still holds fine. Be sure to install the small screen in the top of the tank valve to keep out all but very fine junk. The sediment bulb will filter out most of the very fine rust, if you have any.

[Mike V. Florida]

Take a look at this site to better understand what is happening,

http://modelabasics.com/carb%20basics%202.htm

The GAV is not a shut off valve. Closing it will not do anything to keep the fuel from leaking. Turning the GAV enriches or leans the fuel mixture flowing through the "Cap Jet". The "Cap Jet" is used at low speeds, the flow rate of the fuel to the "Cap Jet" is controlled inside the cab with the "GAV" adjustment knob. Turning it left (clockwise) enriches the fuel mixture for the "Cap Jet".

The only thing that shuts the fuel to the carb is the fuel shut off on the firewall or your Vicky.

Leaking carbs can be caused by several things but most likley of these in a carb that has otherwise been working fine is the float valve not closing correctly due to debris and allowing the fuel past the valve and overflowing the bowl.

[Joe K]

Leaking carbs can be caused by several things but most likley of these in a carb that has otherwise been working fine is the float valve not closing correctly due to debris and allowing the fuel past the valve and overflowing the bowl.

Mike's right on and you can check this by methods given in below link. Also the link is probably THE WAY to rebuild a Zenith.

You want to pay particular attention to the 5/8" level (you'll see how to check this.)

This is the same info I paid good money to the author for his booklet. I hope he is being compensated somehow for this on the 'net.

http://modelabasics.com/Carb/ZenithC...l2011-2007.pdf

Joe K

[Steve Wastler]

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You'll find a zenith to be an easy rebuild, very hard to mess it up, if your jets are numbered they most likely are original, use those not the ones in a rebuild kit.

[Tom Endy]

Originally Posted by Joe K

Mike's right on and you can check this by methods given in below link. Also the link is probably THE WAY to rebuild a Zenith.

You want to pay particular attention to the 5/8" level (you'll see how to check this.)

This is the same info I paid good money to the author for his booklet. I hope he is being compensated somehow for this on the 'net.

http://modelabasics.com/Carb/ZenithC...l2011-2007.pdf

Joe K

Joe K:

You should not have been required to pay anything for the web article you posted here. I am the author of it and it is free to anyone who wants to download it. The article has been posted on the Orange County Model A Ford Club's (Southern California) web site in the technical section at www.ocmafc.com for several years. No compensation is necessary, and I appreciate your kind words.

Tom Endy

[mot]

tom
that is a great article
thanks so much for your great work

[Mike V. Florida]

Originally Posted by Joe K

This is the same info I paid good money to the author for his booklet. I hope he is being compensated somehow for this on the 'net.
Joe K

Who did you pay?

[Joe K]

Gosh, not sure unless I'm thinking of the Pargeter book that is out there.

Sorry. Didn't mean to get everyone riled up.

And it is a great article. And you can't beat the price.

Joe K

[SteveB31]

You have two problems. A float valve leaking and a partially plugged carb, vacuem (air) leak, or plugged fuel source to the carb..


The float valve is what is causing your leak.

The plugged carb, air leak, or plugged fuel line is likley the cause of your popping (backfire).

You may also visit www.model-a.org and follow the troubleshooting pages.

Steve Becker
www.modelastore.com

[Benson]

Additional items to look at for the flooding problem:

1. Might help to check the float for a hole that allows gas inside so float sinks. Remove pin and float then shake float ... listen for gas inside.

If completely full of gas then, will not slosh around BUT then it will weigh too much, compare to a good float.

2. Check the float pin area that holds the float to the bracket ... sometimes the two sides of float bracket are bent and are too close together and the float does not move freely.

3. Sometimes the brass float pins can be bent and binds inside the tube on the float as it goes up/down.

4. If float is bent it can hit the side of the float bowl and bind up.

5. Sometimes the float pin will fall out on one side during installation of the lower casting and the upper casting.

Note that some of these can make float stick either up or down so sometimes too much gas sometimes not enough gas!

[Joe K]

You can check your float by boiling water and then plunging the float into the quiescent hot water: the temperature causes the air within to expand and a leak will be evident by the bubbles.

And all this talk of other issues reminds me that we're now burning 10 percent ethanol: the needles on many carburetor rebuild kits have a rubber tip which can become softened and sticky from the alcohol. I have a John Deere 110 tractor that ALWAYS wants a stout rap with a small hammer at the beginning of the season to free up the float. It works fine afterwards and mostly for the rest of the season.

Joe K

[Maclab58]

I opened it up yesterday and it was full of crap. I cleaned it out and reset the float( it was way too high) running Better now with no leaks! Thanks guys.

[Tom Wesenberg]

Don't overlook cleaning the cast iron sediment bulbs. I picked this one up at a swap meet.

[Christoph]

I had the same prob
In my case, the GAV-valve was stuck and by turning the GAV-handle ,
the complete GAVvalve+seat was to be turned in the carb-housing.
Let someone turn GAV-handle and spot the carb.

btw
good idea to open the carb and clean it too....