Zenith carb fuel drip

[billybronco1]

Okay I know my fuel shut off is not shutting off all the way, so that is my first fix but I assume I need to run the tank dry or pump it out to change. But if the needle valve is doing it job and you left the fuel on should the carb drip at all? I did pull the carb apart and clean everything but still have a fuel drip. I see I already have a little rust in my sediment bowl so there must be rust in the tank as well.

[Tom Wesenberg]

How long have you had the car? Have you flushed out the tank? Have you installed the tank filter?

I lost a full tank of gas over the winter, when I first bought my A. I removed the tank valve and the carb valve and lapped them both with toothpaste, and both have been great since then.

Yes, either and both should keep the carb from dripping.

[billybronco1]

I have only owned the car for about six months and only put 25 miles on it when I had to pull the rear end and rebuild. Everything is back together and I'm waiting for a nice day to go for a cruise. Ok mean while I will pull the carb and clean the needle & seat again, drain the tank and pull the shut off valve and clean and see what happens - thanks

[Maclab58]

Can you explain how you lap a float valve? I have a new one in my cabriolet that had a minimal random drip but I didn't get the gas valve all the way off last night after takin the grand kids out to look at Christmas lights. I awoke this morning with the house smelling like gas and a big puddle in the garage floor. Needless to say, grandma was not happy.

[Gooseloony]

Does it drip from carburetor from here? Mine too, still haven't figured it out. Tom are you saying toothpaste around float valve threads?

[Mitch//pa]

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i use the viton tip float valve on all my carb work and never had any trouble. there were reports of a bad batch of them years ago containing debris that needed to be cleaned out but i have never encountered that. also use the pencil filter in the shutoff and i recommend the filter in the sediment bulb to also trap garbage. this has worked for me so ill continue to stick with it.

[Tom Wesenberg]

Lapping the carb valve was a bit tricky. I pushed toothpasted into the hole for fuel, but the valve is held captive in the seat and only a very short piece of it sticks out enough to barely get it into the chuck on my drill. I lifted the seat on and off the valve as the drill spun the needle. I think I pushed in more toothpast and repeated this a few times, then rinsed it out with hot water. Be sure the seat is screwed into the carb top with a good gasket, so gas doesn't leak around the threads.

The tank valve needs to come apart to lap it. I removed the nut and spring the applied toothpaste to the tapered valve and hand spun it several turns to lap it in. I may have even started with a bit of fine valve grinding paste and finished with toothpaste. It was almost 20 years ago that I did this.

[Maclab58]

Thanks Tom, will try that this afternoon.

[Purdy Swoft]

The Zenith carb will continue to drip if the height of the cap jet or the main jet is below the level of the gas in the bowl of the carburetor. Many of the repro jets sold in kits are too short. If more than one gasket is used under the main jet it will cause the tip of the jet to be too low and will drip and cause a leak. If the float level is too high it will cause a leak plus cause the engine to stall when braking . If the needle seat or main jet isn't tightened properly it will create a leak . Some of the main jet and needle seat gaskets are said to leak worse than others. Most Zenith carbs will be damp on the bottom for one reason or another some will drip others will pour if the float has a small hole, collects gas and gets heavy. There are many possibilities. Sometimes you can stop them from leaking for a while but sooner or later they will begin to get damp again . good luck

[BILL WILLIAMSON]

Take your fuel valve to a hardware store, they have a pet-cock type valve that fits PERFECTLY, for about $4.99 (CHEEP!) & problem solved FOREVER!
Those antique design valves even leaked on BEER BARRELS!!!
Bill W.

[johnbuckley]

Originally Posted by billybronco1

....But if the needle valve is doing it job and you left the fuel on should the carb drip at all?.....

. The needle valve is primarily a metering device- the gas shut off valve is a gas shut off valve. I suspect that most ( agreed, not all!) needle valves will leak slightly if left long enough. Switch off the shutoff valve when leaving the vehicle. Of course electric or mechanical fuel pumps on later vehicles made the need for a gas shutoff valve redundant.

[Brentwood Bob]

I think the best practice is to shut off the main gas shut off valve before you kill the motor, and let the motor run the carb bowl dry. Especially, if you park in a garage attached to the house, or has a spark source, gas water heater, or has a odor sensor(wife).
I do this in my carport because I have lost gallons of gas due to a poor memory.
Bob

[mshmodela]

Originally Posted by BILL WILLIAMSON

Take your fuel valve to a hardware store, they have a pet-cock type valve that fits PERFECTLY, for about $4.99 (CHEEP!) & problem solved FOREVER!
Those antique design valves even leaked on BEER BARRELS!!!
Bill W.

And likely why my car came with a 2nd inline shutoff valve.

[larrys40]

Originally Posted by Purdy Swoft

The Zenith carb will continue to drip if the height of the cap jet or the main jet is below the level of the gas in the bowl of the carburetor. Many of the repro jets sold in kits are too short. If more than one gasket is used under the main jet it will cause the tip of the jet to be too low and will drip and cause a leak. If the float level is too high it will cause a leak plus cause the engine to stall when braking . If the needle seat or main jet isn't tightened properly it will create a leak . Some of the main jet and needle seat gaskets are said to leak worse than others. Most Zenith carbs will be damp on the bottom for one reason or another some will drip others will pour if the float has a small hole, collects gas and gets heavy. There are many possibilities. Sometimes you can stop them from leaking for a while but sooner or later they will begin to get damp again . good luck

Purdy's words are good ones to heed....Carbs are simple yet not. Here's some of my experience and 2 cents worth. As you indicated dirt in the fuel, especially if you have a dirty tank ( rust and debris) that you can ( and probably will ) continue to have needle and seat issues. It could be as Purdy said because the float level is too high for the jets. The main and cap jet need to be above the level of the fuel in the bowl... or they will weep over. A quick check is to take too fingers and put them in the throat ( car not running) ... if they are wet then you have fuel either leaking at the base of the jet or more likely topping the jet.
This can be either because of a improper set float level or the needle and seat not working/seating properly. Check to make sure you only have one gasket underneath main jet.

Needle and seats are a problem. I just spoke to Steve at Berts a while back and will be trying some of his seats. All seats must/should pass a vacuum test. If they won't hold vacuum with the vacuum pump without leakage they will leak fuel. The vitons are great but like clean fuel without debris and used often. The older steel seats have various success or failure rates. I haven't had much luck lapping them with toothpaste.... Once in a while I can stake a metal seat with a light tap ( never a Viton as you will damage the seat contact area) and it helps some. As I said use a vacuum pump to check leakage of it. Snyders/Brattons Vitons are good...

You can bench test a carb too by mounting the carb on the bench vise as it would be on a car... use a fuel fitting with a small tube and funnel up and fill the carb bowl to level with fuel remaining in the funnel. If it leaks out it's not seating.. If it doesn't and holds overnight I feel pretty good about it... That is only after it passes my vacuum test.

There are guys out there that do some good carb rebuilds as their only thing... maybe they have more to chime in. Only my years of experience of rbuilding/doing service/restoration and teaching from my mentor and since past on friend Terry Oberer.

Also, if you don't want it to leak on the floor, use tin foil around the carb bottom going up to create a diaper so to speak.. This will tell you exactly how much fuel you're leaking while sitting. Don't forget to remove before starting!!

And finally, You also must have a proper sealing and functioning shutoff. Regardless of the carb, it must seal off the fuel when shut off. The new repros seem to have a good track record now from the junk ones years back. I'm confident that with proper fixes/tests, float levels set that it will fix your leak. FYI... get that air maze filter off of there! A firebomb waiting to happen for sure.

Larry Shepard

[Mitch//pa]

i also agree you need a good shutoff to work in conjunction with the float valve....

[billybronco1]

Please tell what a "air maze filter" is?

[larrys40]

Originally Posted by billybronco1

Please tell what a "air maze filter" is?

I mistakenly took the image off one if the other posts below yours my apologies . The air maize filter is an aftermarket air filter in the throat if the carb. The model a didn't originally have one and it was made in the day as an accessory item. They do ok to filter out rocks and light debris but honestly can be fire hazards , especial with the paper filter elements . It would be better to have one mounted higher wit a drain hike drilled to drain any collection of fuel

Larry s

[Maclab58]

Can I use- fine valve lapping compound instead of tooth paste?

[tbirdtbird]

never trust a float valve on a gravity feed fuel system, no matter how good you think it is

[Tom Wesenberg]

Originally Posted by Maclab58

Can I use- fine valve lapping compound instead of tooth paste?

Yes, that should lap the valve OK, unless it has some very deep scratches.