flooding Zenith carburetor

I

izze_8

Junior Member
Hello everyone,

I recently inherited my grandmothers 1930 Model A. I have been tinkering with it the last few days. I am finally able to get it to fire and idle for about 7-8 seconds before it will die. Then each subsequent start will idle for a little less, until the carburetor floods. I let it dry out for an hour and the process repeats.

The car was in Colorado before coming down here to Texas. So the fuel to air mixture was set for high altitudes I think. I have adjusted the fuel screw to allow more fuel to balance all the extra oxygen here. This is how I got it to finally turn over and idle for a bit.

Also, I have the throttle lever all the way up (closed). If I give it any gas once I get it started, it will die right away. I also have the GAV open about one half turn.

I am very, very new to this. I was never a car person, but I do have a pretty good technical ability. I would appreciate any help I could get on this flooding issue. And beware, I am going to be coming back here often for help. :)

Thanks!
Christopher
 
Go on line to www.ocmafc.com (the web site of the Orange County Model A Ford Club of Southern California). On the menu at left scroll down to "tech articles" and click. It will bring up a new menu. Click on my name at the top (Tom Endy) and it will bring up a series of articles. They are all adobe files and you are welcome to download and use any of them.

There are several articles on the Zenith carburetor you are welcome to use. Remove the gas cap and try to run the engine. The vent hole in the gas cap may be plugged. Also remove the strainer at the front of the carburetor (5\8" hex) and clean it.

Tom Endy
 
Sounds like fuel blockage. Start by making sure it has a screen in the fuel shutoff valve. This is an aftermarket add-on item that will keep junk from scoring the valve and blocking passages in the carb.
 
I will take a look at those docs. Thank you for the resource. I will try your suggestions and get back to you with the results. I appreciate it.

Tom - I disconnected the fuel line from the carb and fuel did flow out at a pretty good rate. But that screen will be something I will invest in.

Christopher
 
Actually this sounds as though the carbs not getting enough fuel rather than flooding- it sounds as though you're just using up whats in the bowl.
Disconnect the fuel inlet at the carb and check you've got a good flow through the pipe from the tank. There could be rust crud blocking the exit from the tank or possibly crud blocking the strainer ( the brass nut at the front of the carb). Rusty bits blocking fuel flow is a common scenario on cars that are resurrected.
 
Very simple basic question not to be overlooked:

If the gas tank had "old" gas, or new ethanol type gas stored in the tank for a spell, did you drain the tank of this possible less than good or contaminated gas & provide new fresh gas?
 
The car was drained of all fluids for storage over this last winter (except oil). I am using regular gas with a lead substitute right now. Before these last few years, my uncle pulled the gas tank and drained it, then cycled the engine a few time with good new gas. I think this is what was done. I am a little fuzzy on the details.

I also forgot to mention, that this is a fairly new carb. I think it was replace within the last 9 months.
 
Carburetor "Flooding" or "Starvation" ????

1. Immediately after your engine dies in the 7-8 seconds that it runs, try feeling the underside of your carburetor & also the inside rear of the carburetor inlet near the choke to see if you feel "wet" gasoline.

2. Next, about 15 minutes after your engine dies, try feeling the underside of the carburetor & also the inside rear of the carburetor inlet near the choke "again" to see if you feel "wet" gasoline. (I.e., fuel overflow & dripping).

3. With this simple test, many times one can determine if one has fuel "flooding" problems by feeling "wet" gas, or fuel "starvation" problems by not feeling any "wet" gas.

4. The one (1) hour wait before your engine starts again can either mean that:

A. The excessive fuel has to evaporate & dry out in the combustion chamber & intake manifold before it starts again; or,

B. "If" fuel starvation, it takes this one hour for the carburetor bowl to get replenished with fuel because of fuel blockage or fuel starvation causing very slow fuel flow to the carburetor bowl.

Hope this helps as a start.
 
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Thank you all for the information. The responses here are amazing!

H. L. - I am getting fuel leaking out near the air filter. I have a pan to catch it all since there is a good amount that drips after the engine dies. So this leads me to believe it is flooding.

Tom Endy - Those documents helped a lot. I realized that I am adjusting the air/fuel mixture in the wrong manner.

I still have a ton to learn. Thanks for bearing with me as I figure it all out.
 
I am in Richardson, about 20 minutes north or Dallas. Near HWY 75 and 635. Can you recommend a local club in that area?
 
Whether you think you need it now or not, just get a very helpful "Carburetor Fuel Level Gauge" for under $8.00 -- comes in handy especially with a Zenith which causes problems at turns & sudden stops.

Appears your flooding is being caused by the carburetor float valve allowing too much fuel to enter into the carburetor bowl because either:

1. The carburetor float is not adjusted properly to close the float valve after the correct amount fuel enters the bowl; or,

2. The carburetor float has a hole in it whereby it does not float; hence, it sinks & allows too much fuel to enter; or,

3. Your carburetor float valve is not sealing properly because of wear, or debris in the valve, thus not stopping the flow of fuel; or,

4. Some of the jets are too short or have worn gaskets which are not sealed; or, a few other things too lengthy to mention.

Mr. Endy's written information mentioned in replies above can greatly assist in any further diagnosis to help correct your flooding problem.

Hope this helps to begin to understand "Flooding".
 
Izze, You might try opening the mixture adjustment a full turn and a quarter when the engine is cold, then close it up after the engine has warmed up.
 
izze 8,
After waiting for the carburetor to dry out, remove the air filter and try to start it again. Sometimes an air filter can cause the flooding condition.
Supergnat
 
Ok, I read over all the documentation I could find. I am able to get the engine to start and stay idle. But, I have to keep the choke pulled out some ways.

I pull the choke, hit the starter, release the choke after one turn of the engine. It fires up. I lower the spark lever. Then the engine starts to sputter. I pull the choke out about an inch or so and the idle levels out and starts to sound really nice. I can open the throttle at that point, and the engine seems to function normally. But I just need to keep the choke pulled out or it will sputter and die. I have the choke knob open about 10 turns already.

So I assume that the carburetor is still getting to much air somehow. I have the air screw open one full turn. I guess I can close it off a little more. But, how far I have to hold the choke is concerning me.

The good news is that the carb did not flood!
 
1. If too much air is entering the combustion chamber, it could very well be that your intake manifold "gasket(s)" are leaking & sucking in air where it joins the engine "or" where it joins the carburetor flange.

2. Very common with cheap "steel" manifold gaskets which have rusted out over time.

3. If these two (2) intake joints are not sealed air tight, "no" adjustment on the carburetor will make your car run better.

4. One vintage method to test for intake manifold leaks is to carefully squirt a very small amount of lubricating oil on the entire length of the intake manifold gasket "while" the engine is running.

5. If the engine rpms increase, it is because the oil "temporarily" seals the "excess" air flow for a "few" seconds.

6. If this rpm increase happens, new manifold gaskets are needed; or,

7. The intake/exhaust manifold is out of alignment & needs to be milled or filed with a flat file until one achieves near perfect alignment at the manifold gaskets.

8. Best to get more durable copper clad gaskets if new gaskets are needed.

Hope this one additional tip helps you to get to the "root" cause of this seemingly carburetor problem -- the above occurs often on vintage vehicles.

Added Notes:

A. Also check your carburetor gasket between upper & lower halves of your Zenith to insure it is sealed.

B. If no air leaks anywhere, very possible too little fuel; hence, fuel flow blockage between combustion chamber & fuel in fuel tank.

C. Don't feel like the Lone Ranger -- this is a Model A thing which can easily be corrected by any Model owner every 30 years or so.
 
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Suggest you join the Dallas Model A club . Lots of Gurus in that club . One being Ken Davis the A/C,shock guy.
 
I run the GAV (choke knob) open about 1/4 turn on Zenith one and two carbs after warm up. With the GAV open 10 turns is way, way, too rich. Running the GAV too rich will cause loping and black smoke from the exhaust but won't cause flooding and dripping at the carb. It sounds like fuel starvation is the problem. I've found that the stand up filter in the cut off valve is a necessity in most cases. I would install the filter and clean out the fuel lines and the carb. It could be a blocked vent at the gas cap. If the fuel line protrudes too far past the ferrule on either end of the fuel line that connects from the firewall filter to the carb, it will enter too deeply in the carb or filter and restrict flow. It could be partially blocked micro filters causing starvation. I only use mesh filters and avoid micro filters, Too many filters as a modern style filter installed in the fuel line can cause problems because most aren't designed for gravity flow. I think that over chokeing to overcome starvation of fuel causes the flooding. When you turn the gas on, if the carb doesn't start leaking, before trying to start. the problem is probably not the float or needle valve. I don't think that adjustment is the main problem. The begining adjustment of the idle adjust screw on top of the carb is one and one half thrns off the seat. Normal adjustment of the GAV is 1/4 turn off the seat after warm up or one full turn off the seat in cold weather untill warm up, usually a short time until the engine begins to lope. You may need to open the idle speed adjustment screw on the throttle lever at the carb. If the throttle butterfly is adjusted completly closed, it won't idle.
 
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