Carburetor Fowling

E

Ed in Maine

Well-known member
As part of my major tune up of my Victoria I decided to open the carburetor and just look things over. It has been 2 years since I rebuilt the carburetor. The inside of the carburetor looked very good. There were a couple of specs of dirt in the bottom of the bowl but they were very tiny. Next, I checked the flow rates on all the jets. I have the tester that uses a 36 in column of water to check the flow rates along with a graduated cylinder to measure flow in ml/min.
I was disappointed to see that the flow rates had dropped off about 4-5% on all the jets. The cap jet is less critical and in most cases will not be a problem. This means that with time and use, our carburetors are being fowled with the lousy gas. The inside of the jets are being coated. I soaked the jets in Barrymore cleaner and hosed them out and in most cases the flow rates came back to my restored values. Perhaps we should be periodically using a can of carburetor/fuel injector cleaner. Ed
 
I pour in 1 oz per gal of Seafoam every fill up. Claims to clean jets and absorb water, two issues we see with our gas these days.

I am convinced that Seafoam does do some good. It freed up my fuel gauge in my '06 F-150. The gauge had stuck at ¼ tank when it sat for a while during Covid. Saved me from pulling the tank.
 
If fowling, move the L to just after the F and everything will be flowing fine. :D:D

Otherwise use one of the injection system cleaners that go in the tank, available at the auto parts stores.
 
Since you're running a Zenith, I'm wondering if it's possible that the water and alcohol in our modern gasoline are causing some corrosion of the iron carb body and is possibly microscopically dissolving some of the iron casting and leaving the deposits you mentioned in your jets and passageways. Just a thought, but I don't have any evidence to back it up.

I guess it's a "marvel" that I haven't had any issues like that yet - I'm running a Marvel carburetor and add Marvel Mystery Oil to every fill up. :D Since the Marvel is a pot metal casting it wouldn't be a victim of rust that could easily form in an iron body Zenith. Occasionally I do use Seafoam and agree that it's a good product and probably helps more than we know.
 
Ed, I’m very impressed that you would dive in that deep as a part of a tune up. We’re you experiencing any notable performance symptoms with the reduced fuel flow? Put me down as another satisfied Sea Foam user I run it in every single engine I have except for my daily drivers (they get a different additive). I have not had a carburetor problem since I started using it 25 years ago. Ethanol is basically water and if allowed to sit without a stabilizer “phase separation “ starts which means that the water will separate from the gasoline and settle to the bottom of the container (gas can, gas tank, carburetor,etc.) (a friend of mine has a boat with a 100 gallon aluminum gas tank. To save money he was buying gas at a gas station rather than the marina. When his motor puked they found 16 gallons of water in the bottom of the gas tank). If allowed to sit it will indeed rust the bottom of the float bowl in a Zenith. It can cause even worse problems in a Marvel or Tillotson. I don’t know enough about fuels to even guess what is building up inside the jets.
 
So if the jets are being fouled by the fuel, what fuel are you using ? Ethanol or non ?

I can see it with ethanol especially if the car sit for awhile between runs.

I'm a big fan of Sea-Foam, it works. Can't say the same for some others.
 
jeepguy1948 said:
Ethanol is basically water and if allowed to sit without a stabilizer “phase separation “ starts which means that the water will separate from the gasoline and settle to the bottom of the container (gas can, gas tank, carburetor,etc.)
Click to expand...

Ethanol is hydroscopic and absorbs water from the atmosphere. In a modern with a sealed fuel system it is not so much of a problem. In our cars that are vented to the atmosphere, then it becomes an issue
 
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