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TJMack · 02-20-2018, 08:05 PM

Addendum: The saga continues. All is not as well as I thought. There’s still a leak. The new tank valve did stop the leak when it is turned off, but not when it’s left on. At least I’m seeing some progress. J

This afternoon I left the tank valve on when I got done with my drive just to verify that the leak stopped. At first there was no leak. I didn’t check it for a few hours, but when I finally did, there it was, the infuriating drip out the throat of the carb.

Tomorrow I’m going to try a few things, one at a time. The first is I’m going to split the carb and then dry the area around the float valve real well by spraying it with brake cleaner and let it evaporate.

Then I’ll hook up the gas line to the upper half and invert it so that the float valve is closed by the weight of the float. I’ll turn on the tank valve then inspect the carb for any indication of where the gas comes out, if it does.

Hopefully this will give me a lead on what needs fixin’. I’ve already looked for cracks in the casting, but they could probably be so small that the eye can’t see them. When I changed the float valve I inspected the casting where the gasket goes and it looked OK, no major pits. So I don’t know what to expect.

If this experiment turns up nothing I’m going to expand on Yblockhead’s theory. I noticed that my fuel line is slightly kinked. Maybe this is reducing the head pressure to where it’s not enough to maintain the fuel level. I KNOW…. It’s a reach but I’m getting desperate.

Another thing, other than Yblockhead’s theory, that makes me suspect of the fuel line is the fact that the see-through fuel filter I have just in front of the carb inlet quite often looks empty even with the engine running fine. It seems that once the float valve opens the filter should fill with gas before the carb reservoir.

To further complicate this mess is the fact that I’ve had trouble with the condenser overheating. That’s another long story for a different thread, but I fixed that with a heat shield that I made and put under the distributor.

The reason that this may be germane to the conversation is that in testing my heat shield I let the car idle for 10 minutes or more after a good warm-up to test the effectiveness of the heat shield.. Before the heat shield I couldn’t get it to run for more than a few minutes if I stopped and let it idle. As it sat there idling I was watching the fuel filter. It always looked empty, but I could see a very faint trickle of gas passing through if I looked real close..

It finally did stop running, but I thought it ran out of gas by the way it stopped. I carefully took out the drain plug in the bottom of the carb and sure enough, nothing came out.

I still haven’t figured this one out but I’m thinking Yblockhead’s theory might be in play.

1930 Coupe, one of the first things I did was the blow test. It suggested that everything was OK. I’d like to have my vacuum tester that I have up in New York down here in Florida. It would be more conclusive I think.

Gary Wa, thank you for that link. That looks very interesting. I'll have to spend some time there;.

02-20-2018, 08:05 PM	#13
TJMack Member Join Date: Mar 2017 Location: Venice, Fl and Marcy, NY Posts: 93	Re: Leaking Zenith Carburetor Addendum: The saga continues. All is not as well as I thought. There’s still a leak. The new tank valve did stop the leak when it is turned off, but not when it’s left on. At least I’m seeing some progress. J This afternoon I left the tank valve on when I got done with my drive just to verify that the leak stopped. At first there was no leak. I didn’t check it for a few hours, but when I finally did, there it was, the infuriating drip out the throat of the carb. Tomorrow I’m going to try a few things, one at a time. The first is I’m going to split the carb and then dry the area around the float valve real well by spraying it with brake cleaner and let it evaporate. Then I’ll hook up the gas line to the upper half and invert it so that the float valve is closed by the weight of the float. I’ll turn on the tank valve then inspect the carb for any indication of where the gas comes out, if it does. Hopefully this will give me a lead on what needs fixin’. I’ve already looked for cracks in the casting, but they could probably be so small that the eye can’t see them. When I changed the float valve I inspected the casting where the gasket goes and it looked OK, no major pits. So I don’t know what to expect. If this experiment turns up nothing I’m going to expand on Yblockhead’s theory. I noticed that my fuel line is slightly kinked. Maybe this is reducing the head pressure to where it’s not enough to maintain the fuel level. I KNOW…. It’s a reach but I’m getting desperate. Another thing, other than Yblockhead’s theory, that makes me suspect of the fuel line is the fact that the see-through fuel filter I have just in front of the carb inlet quite often looks empty even with the engine running fine. It seems that once the float valve opens the filter should fill with gas before the carb reservoir. To further complicate this mess is the fact that I’ve had trouble with the condenser overheating. That’s another long story for a different thread, but I fixed that with a heat shield that I made and put under the distributor. The reason that this may be germane to the conversation is that in testing my heat shield I let the car idle for 10 minutes or more after a good warm-up to test the effectiveness of the heat shield.. Before the heat shield I couldn’t get it to run for more than a few minutes if I stopped and let it idle. As it sat there idling I was watching the fuel filter. It always looked empty, but I could see a very faint trickle of gas passing through if I looked real close.. It finally did stop running, but I thought it ran out of gas by the way it stopped. I carefully took out the drain plug in the bottom of the carb and sure enough, nothing came out. I still haven’t figured this one out but I’m thinking Yblockhead’s theory might be in play. 1930 Coupe, one of the first things I did was the blow test. It suggested that everything was OK. I’d like to have my vacuum tester that I have up in New York down here in Florida. It would be more conclusive I think. Gary Wa, thank you for that link. That looks very interesting. I'll have to spend some time there;.