Zenith carb float valve problem

[springerpete]

This is a rebuilt Zenith carb. Float valve does not shut completely off. Valve has been replaced twice. Once with original style and second time with the ball style. Float level has be verified with the fuel level apparatus. I think the only issue left is that the float valve does not shut completely off as carb leaks out of the vent hole. Suggestions ? Thanks, Bill

[Growley bear]

Before assembling the carburetor if you hold the upper half with the float and valve installed the float seam should be one inch from the gasket surface; no gasket installed. I blow through the fuel inlet to check the seal of the float valve. A leak can be heard. That is a quick check that I have used for over fifty years. If the valve passes that test there shouldn't be a leak, providing the rest of the carburetor has been properly assembled.
There are some good books available on rebuilding the Zenith carburetor. Also some good advise with pictures on this forum.

[Tom Wesenberg]

I bought a brass hand vacuum pump from H/F and use that to confirm a tight seal at the needle and seat. I recently used it to verify the leaks on a couple of Honda carbs, and it also verified the fix worked well.

[Will N]

Check that the float is not binding against anything. I had a ridge in the casting of interior of the bowl. When the carb was cool, no interference, but when it heated up the float would catch on the ridge and would not shut the valve.

[100IH]

Check on the arm of the float where the needle contacts the arm. Old floats can wear a dimple into the arm and the replacement needle can catch and bind up there. Solution, sand the edges to blend the dimple into a wide depression.

[H. L. Chauvin]

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FWIW:

One (1) humble opinion on a most common, Model A fuel leak problem many will not want to pay for nor even admit.

1. Appears if we have a Model A carburetor float valve leaking problem, we are definitely in the Model A owner "majority" with having such constant leaks; however,

2. Appears also if we report that we have a constant Model A carburetor float valve leaking problem, we are in the Model A "minority", because very few of us Forum members want others to think that we are not perfect, and we are not great Model A mechanics who cannot resolve what appears to be such simple, small Model A mechanical problems. But is it always simple?

3. In my humble opinion, most of our float valve problems stem from our leaking fuel tank shut off valves, and more importantly, from our fuel storage sources further up the fuel line.

4. If our fuel shut off valve never leaks, our carburetor fuel shut off valve would never leak if we shut off the the fuel line first and allow our cars to run until there is no more fuel in the carburetor.

5. The Model A fuel leaking problem source is always further upwards, such as:

A. Our fuel tanks are approaching 90 years old with failing interior original coatings; more rust particles are forming as time goes on; former fuel tank sealers are being dissolved with ethanol gas in some cases; almost 90 years of collecting dirt and other deleterious materials at bottoms of tanks are still there, all of which break down, lodge in our soft brass fuel shut off valve and causes this fuel shut off valve to leak.

B. Next, with our engine operating, with our shut off valve opened, these same very fine fuel tank impurities pass through our fuel filtration system, and lodge in our Model A carburetor float valve, and also causes this carburetor valve to leak.

C. An additional problem is our Model A limited use where most problems occur when we do not drive our Model A everyday; hence, just like our Model A valves that collect varnish and get sticky, so do our carburetor float valves.

(Just think, even our bathroom toilets get dirty with clear water, (water clean enough to drink), if we only flush them once every four (4) months.)

D. Another problem is fuel gravity flow where a more modern fuel pump does not quit pumping fuel when our engine stops; hence, with a Model A leaking fuel shut off valve, and a Model A leaking float valve there is constant Model A gravitational fuel pressure exerted from the tank to the overflowing Model A carburetor bowl at all times.

6. Is there .......... without a doubt ....... a 100% positive solution? Yes.

7. But not for most of us Forum members where most of us are a bunch of Tight Wads and far too tight to pay to have this problem properly corrected, such as:

A. Have Mr. Brent in Tennessee "properly" restore the corroded "interior" of our fuel tanks; and,

B. Buy a new fuel shut off valve and new carburetor float valve; and,

C. Last but not least, drive our Model A more often to keep fresh fuel flowing at all times.

Hope this helps any future Model A owner whose house and garage could burn down to the ground because of a parked Model A leaking lots of gas through an overflowing Model A carburetor bowl.

[CWPASADENA]

Originally Posted by Tom Wesenberg

I bought a brass hand vacuum pump from H/F and use that to confirm a tight seal at the needle and seat.

Good idea.

I had a problem where the fiber washer under the needle and seat would not completely seal. I found the surface on the upper part of the carb under the needle and seat was a little rough from prior blasting(not by me). I smoothed this surface the best I could and really tightened the needle and seat using a new fiber washer.

Leak stopped.

I would not recommend using any kind of a sealant.

I recently found this problem an another carb that dripped after shutting the engine off.

My experience.

Chris W.

[Kurt in NJ]

I had the problem when I used repro parts, put old one back-- no more problems

[jb-ob]

2 X Kurt in NJ

Some swear by replacement originals, two ball, or Viton tipped float valves....I've sworn at all of them!

Amazing but the original eighty year old, in the car new, valve works flawlessly.

Go figure? JB

[Tom Endy]

The attaché article may be of some help.

Tom Endy

[Terry, NJ]

This is probably the original 85 YO float, in which case the float may not be Floating! They do spring leaks occasionally and sink and they are useless for sealing anything. Heat it very gently and see if there is a jet of vapor anywhere. About 125 degrees will do it, at the upper end of what you can touch. Any hotter and you may be melting the solder.
Terry

[BILL WILLIAMSON]

Just submerge the float in WARM water & see if it bubbles----
Bill Simple

[Ed H.]

Originally Posted by BILL WILLIAMSON

Just submerge the float in WARM water & see if it bubbles----
Bill Simple

One can also weigh on a mailing scale. If over spec's float is leaking and sinking. I have also reused the orig needle and seat which in my case is steel.

[BILL WILLIAMSON]

Does the USPS have a float weight chart?
Bill Blind

[Benson]

The Original floats (without extra solder repairs) which I have weighed and the Repros weigh 1.1 oz. with the exception of "Made in Argentina" ones from the 60's. I do not use these as they are generally flimsy and bend easily.

The Argentine ones weigh less as I remember. I think J.C. Whitney s.s. Warshawsky and Ricks sold these.

[Bikerider58]

Originally Posted by Tom Wesenberg

I bought a brass hand vacuum pump from H/F and use that to confirm a tight seal at the needle and seat. I recently used it to verify the leaks on a couple of Honda carbs, and it also verified the fix worked well.

How do you check the seal? Hose adapter for fuel inlet and flip the carb upside down?

I could not get a modern valve to seal consistently, but gouse ball valve worked. Bench testing would have been better than installing and removing many times.

My petcock /shut off doesn’t with about 2 bowls leaking a day. It gets replaced next week.

[redmodelt]

Something was touched on above, the gasket. My op is a lot of the gaskets used in Model T and A kits are too hard for the job. As said also, look how old these carbs are, there are imperfections in the castings after years of use.
Suggestion;
This is something I have doing with the same valve in Model T carb. I take lead sheeting and reduce the thickness to same as needed and punch out a gasket. The soft lead seems to seal better.

[Tom Wesenberg]

Yes, I used a rubber hose to couple the vacuum pump to the Honda carb, then turned it upside down and pumped 20" vacuum.

[johnbuckley]

Springerpete, you're sure unlucky to have two consecutive non functioning float valves. I must admit several brand new ones of whatever design have been no good and I now check them all.
here's a list of causes of leaking of Zenith ... the float valve nearly always get blamed first of all. ( though often innocent !)
Zeniths: Causes of leaking
Problem: Remedy
1 Leaking/loose float valve gasket: Tighten/reseal/replace
2 Leaking float valve: (or crud stopping it sealing) Replace ( or clean up if possible)
3 Friction on float hinge: Loosen
4 Incorrectly set fuel level: Re-set
5 Hole in float: Repair or replace
6 Too many gaskest on main jet Check
7 Cap jet or main jet too short: Replace
8 Leaking/loose gasket at main jet: Tighten/reseal/ replace
9 Leaking /loose gasket at cap jet: Tighten/replace
10 Leaking or loose GAV housing threads: Tighten/ reseal/ replace
11 Leak at fuel inlet union: Tighten/reseal/replace
12 Loose/leaking gasket at strainer: Tighten/reseal/replace
13 Loose/leaking gasket at drain plug: Tighten/reseal/replace
14 Cracked housing/leaking passage plugs: Repair or replace

1-7 will generally manifest as poor running.
8-14 will generally not affect running unless there is excessive leaking.