Zenith carb #12 03 14991B question

[Max4Me]

1925 Maxwell/Chrysler, carb question. I originally posted about it probably two years ago. I had taken it for about a 50 mile drive, and it ran fine the whole time. I parked it in the garage and it shut down fine (no backfire, etc.) It has not started since. I will not list all of the other things I’ve tried. People on the forum and people I have talked with at a local club have all said it’s the carburetor. The car came equipped with a Zenith carb with an ID tag that says 12 03 14991B. I have pulled it apart, put it in a parts cleaner, pulled out every jet (orifice? port?) and verified each is clear, same for every passageway. The floats float, and the needle valve slides in and out easily and the rubber tip is not marred. While apart, I put water thru a fuel line and lifted/lowered the floats and the needle valve allowed water to flow as appropriate (and yes, I dried out the carb after this). I made a new gasket between the upper and lower body parts, making sure all ports were clear. On the outside bottom of the float bowl is a valve that looks like an ice maker water shut off valve. It feeds into a large jet in the bottom of the float bowl and has a pointed end that screws in and obviously controls  the amount of fuel feeding the jet. This jet feeds fuel into the venturi. My question is, what is the proper adjustment to feed the correct amount of fuel?

(or am I way off base?)

 

Thanks, Dave

 

P.S. Pics were taken prior to cleaning.

Edited October 6, 2023 by Max4Me (see edit history)

[carbking]

The suggested initial setting of the adjustable main metering jet is 2 and 1/2 turns from the valve being lightly seated.

 

This will always get the engine started, if the engine has no other problems.

 

The adjustment range is 0 to 5 full turns.

 

An easy way to determine if the carburetor is at fault is to have a helper crank the engine while you spray starting fluid into the air intake. If used, starting fluid should be sprayed WHILE the engine is being cranked. 1 to 2 second spray is sufficient. If the engine starts, then time to check out the carb. If the engine will not fire, other issues exist.

 

Testing is cheaper than guessing.

 

Jon.

Edited October 6, 2023 by carbking (see edit history)

[Max4Me]

Jon,

Thank you for the info as to initial setting for the valve. I will give that a try! As for testing being cheaper than guessing, I totally agree. I won’t expound on what I’ve done in the last two years as this would be an  extremely  long post. Two weird things that I can’t reconcile are that the car ran perfectly on the drive before I parked it but 45 days later it wouldn’t, and hasn’t started. Second, if I remove the plugs and drizzle gas in each cylinder, then hook up everything and try to start the engine, it will start and run until all four cylinders have fired. 

 

I thought about starting fluid but was very concerned about using such a highly volatile substance in such an old engine. After setting the metering valve I may try the starting fluid.

 

Again, thank you for taking the time to answer and give a suggestion for a next step.

 

Dave

[carbking]

OK - you have done a different test to do part of what the starting fluid would test.

 

The cylinders will fire, so the ignition system is working.

 

So either fuel is not getting to the carburetor (test by unscrewing the drain plug on the bottom)

OR 

Fuel is not being sucked into the cylinders (are you using full choke for starting?)

 

Hold off on the starting fluid for now.

[carbking]

Another question.

 

Have you drained the tank, and refilled with fresh fuel.

 

My low compression John Deere will not start on 2 year old fuel unless the engine is started on starting fluid, run at high idle with half choke until hot.

 

Jon

[Max4Me]

5 hours ago, carbking said:

The cylinders will fire, so the ignition system is working.

 

So either fuel is not getting to the carburetor (test by unscrewing the drain plug on the bottom)

OR 

Fuel is not being sucked into the cylinders (are you using full choke for starting?)

Jon,

The engine fires so ignition is working is my understanding as well. Fuel is getting to the carb because a glass filter between vacuum tank and carb has fuel in it, AND when I pull the drain plug at the bottom, fuel runs out. So carb is getting fuel, but what is happening once it gets there? This is why I recently pulled out all the jets to clean them and all passages, thinking somehow something got in and plugged something. I also had all surfaces of the intake and exhaust manifolds surfaced about a year ago in case of leaks. Although, the machinist said he did it ever so slightly because it appears that a piss poor job (a 'G' rated rephrasing of what he really said) had been done before. I also installed Remflex gaskets because they have a little 'give' when compressed to try and make a tighter seal.

 

To add to the mystery, I used to have bee hives. So I took the plugs out, and allowed smoke (not forced) into the carb throat while my son cranked the engine with wide open throttle. Lo and behold, small puffs of smoke came out of each cylinder on the compression stroke. I also smoked the manifolds while he cranked just to see if any smoke got sucked in to indicate a gasket leak. Nope. 

 

Further, I did remove the gas tank when I first got it and washed it out with pea gravel and water.  Some crud came out but not much.  After drying it was reinstalled. To this day, there is very little debris showing up in the glass filter.  I also pulled off the electric fuel pump that was on it. I rebuilt the vacuum tank and replaced some of the fuel line and flushed all of it. It has run beautifully since, until two years ago. As for fresh fuel, it was fresh when I took the drive two years ago, and presumably it would have still been fresh when it failed to start 45 days later. I have not put fresh fuel in the tank itself, but have used a fill bottle with fresh fuel to prime the vacuum tank and fill the carb. I do use full choke, slight throttle, and full retard when trying to start it, just like I always have done.

 

I have not reinstalled the carb since your info on adjusting the valve at the carb bottom. I have to repair the vacuum tank bottom (see the post about repairing a Kingston vacuum tank). 

 

Thank you so much for your time and effort to help solve this issue.

 

Dave

Edited October 6, 2023 by Max4Me (see edit history)