The Ford Barn

TJMack · 02-20-2018, 09:04 AM

I’m new to Model A’s. The one I have now is the first one I’ve ever owned. But I’m not new to carburetors. I’ve worked on them since the late 50’s when I took apart my family’s first power mower, an 18” Roto Rugg.

Over the many years I’ve also worked on carbs from numerous cars, trucks, a few tractors, outboard motors, chain saws, etc, a Chris Craft inboard, even my airplane. But I have to admit this “simple” Zenith on my Model A has caused me more agony than any other I can remember.

I’ll also admit that I never bothered to learn all the theory of operation and detailed workings of a carburetor. I only needed the basic understanding of what did what, and what to do when it didn’t. This usually amounted to cleaning, or at most changing, the float valve (we always called it the needle-and-seat) and making sure the float actually floated. Along with a good cleaning and new gaskets, and I was usually back in business.

Not so with this Zenith. As it turns out, it should have been, but I spent hours chasing my tail on the damn thing.

My first thought was to clean the float valve and make sure the float wasn’t taking on gas. The float valve is one that doesn’t come apart, so cleaning it was a blind operation. Shaking the float I couldn’t hear any sloshing, and actually trying it in both water and gas verified that it, in fact, did float.

Upon reassembly the leak persisted. It took me quite a while to even figure out where the gas was coming out. To make a long story as short as possible, after more attempts at cleaning the valve, I finally figured out that it was coming out the main jet and the cap jet into the throat of the carb.

Now, anyone who has messed around with these has also figured out that the level of gas in the reservoir is critical. That’s because if it’s too high it will leak out the main jet and the cap jet as mentioned above. I found this by taking the bottom of the carb off and slowly adding gas to the reservoir to it to see where it was coming from into the throat. Nothing happened until the level of gas got almost to the top of the reservoir and then out it came. A quick observation showed that the fuel in the reservoir was now above the level of the main and cap jets. As soon as it got below that level the flow stopped.

This may seem obvious, but until you actually do this check, it’s not at all obvious, and hard to see with the carb assembled. You can’t see the fuel level in the reservoir.

Since we all know that the level of gas in the reservoir is controlled by the float valve and the float, I was back to the original thoughts that one of them must be bad. I ordered a new float valve and a new float even though I couldn’t find anything wrong with the old ones, which at some time had already been changed by a previous owner.

Upon installation of the new parts I was hopeful that the problem was solved. Not so. The new float valve leaked as bad as the old one. The float was obviously a waste of money. So was the float valve.

The interesting part of all this is that I reinstalled the old parts and for now at least, it isn’t leaking. I don’t know if I really learned anything new, but it kept me out of the bars, as my Mother used to say. It did verify that not all that is new is necessarily better.

For some reason I hadn’t even thought to check on-line to see if anyone had similar experiences. This is what led me back to the Ford Barn. I had actually signed up for it last year a couple months after I bought the car, but honestly forgot all about it. Dumb, I know, but like lots of people my age I suffer from CRS.

I have since found an EXCELLENT, well written article written by Tom Endy that would have steered me in the right direction if I had only seen it earlier. I do intend to spend some time on the carb when the car sets idle in Florida for the summer. Thanks to that article I feel confident that I can improve it.

One question I have, though. Does a Model A tend to leak if it’s parked on a hill? It seems as though it must if the car is facing up hill. That could place the level of the jets below the fuel level in the reservoir and allow it to leak out which would lower the float and allow more fuel to flow in. Eventually this could drain the tank, I suppose.

I can see why it’s so important to close the shut-off valve under the tank whenever the car is not running.

02-20-2018, 09:04 AM	#1
TJMack Member Join Date: Mar 2017 Location: Venice, Fl and Marcy, NY Posts: 93	Leaking Zenith Carburetor I’m new to Model A’s. The one I have now is the first one I’ve ever owned. But I’m not new to carburetors. I’ve worked on them since the late 50’s when I took apart my family’s first power mower, an 18” Roto Rugg. Over the many years I’ve also worked on carbs from numerous cars, trucks, a few tractors, outboard motors, chain saws, etc, a Chris Craft inboard, even my airplane. But I have to admit this “simple” Zenith on my Model A has caused me more agony than any other I can remember. I’ll also admit that I never bothered to learn all the theory of operation and detailed workings of a carburetor. I only needed the basic understanding of what did what, and what to do when it didn’t. This usually amounted to cleaning, or at most changing, the float valve (we always called it the needle-and-seat) and making sure the float actually floated. Along with a good cleaning and new gaskets, and I was usually back in business. Not so with this Zenith. As it turns out, it should have been, but I spent hours chasing my tail on the damn thing. My first thought was to clean the float valve and make sure the float wasn’t taking on gas. The float valve is one that doesn’t come apart, so cleaning it was a blind operation. Shaking the float I couldn’t hear any sloshing, and actually trying it in both water and gas verified that it, in fact, did float. Upon reassembly the leak persisted. It took me quite a while to even figure out where the gas was coming out. To make a long story as short as possible, after more attempts at cleaning the valve, I finally figured out that it was coming out the main jet and the cap jet into the throat of the carb. Now, anyone who has messed around with these has also figured out that the level of gas in the reservoir is critical. That’s because if it’s too high it will leak out the main jet and the cap jet as mentioned above. I found this by taking the bottom of the carb off and slowly adding gas to the reservoir to it to see where it was coming from into the throat. Nothing happened until the level of gas got almost to the top of the reservoir and then out it came. A quick observation showed that the fuel in the reservoir was now above the level of the main and cap jets. As soon as it got below that level the flow stopped. This may seem obvious, but until you actually do this check, it’s not at all obvious, and hard to see with the carb assembled. You can’t see the fuel level in the reservoir. Since we all know that the level of gas in the reservoir is controlled by the float valve and the float, I was back to the original thoughts that one of them must be bad. I ordered a new float valve and a new float even though I couldn’t find anything wrong with the old ones, which at some time had already been changed by a previous owner. Upon installation of the new parts I was hopeful that the problem was solved. Not so. The new float valve leaked as bad as the old one. The float was obviously a waste of money. So was the float valve. The interesting part of all this is that I reinstalled the old parts and for now at least, it isn’t leaking. I don’t know if I really learned anything new, but it kept me out of the bars, as my Mother used to say. It did verify that not all that is new is necessarily better. For some reason I hadn’t even thought to check on-line to see if anyone had similar experiences. This is what led me back to the Ford Barn. I had actually signed up for it last year a couple months after I bought the car, but honestly forgot all about it. Dumb, I know, but like lots of people my age I suffer from CRS. I have since found an EXCELLENT, well written article written by Tom Endy that would have steered me in the right direction if I had only seen it earlier. I do intend to spend some time on the carb when the car sets idle in Florida for the summer. Thanks to that article I feel confident that I can improve it. One question I have, though. Does a Model A tend to leak if it’s parked on a hill? It seems as though it must if the car is facing up hill. That could place the level of the jets below the fuel level in the reservoir and allow it to leak out which would lower the float and allow more fuel to flow in. Eventually this could drain the tank, I suppose. I can see why it’s so important to close the shut-off valve under the tank whenever the car is not running.