Zenith Fuel Seepage

[Mark Yarrish]

I searched the forum and could not find this exact question. I have rebuilt my carbs and are just getting them sorted out.

I have some seepage on the starter pump side along the flange/gasket area between the carb body and the throttle body.

Although I have not put any Permatex on the bottom plug/accelerator pump valve, I don't see any fuel coming from those areas. I also don't seem to see any fuel on the other side, of the carbs. The side with the idle mixture screws.

I may be imagining it, but it seems that the fuel is seeping through the threads on the bolts coming up through the throttle body. Is this possible? How would I seal this off? I have a new gasket set ready to install, but I wanted to ask what else to do? I have ground each mating side of the body/throttle body on a flat concrete floor with some fine sandpaper. Therefore I believe the surfaces to be flat.

If the seepage is coming through the bolts, is it a bad idea to use some non permanent thread sealer on those bolts coming through the throttle body?

Thanks!
Mark

[Ron LaDow]

The fuel is not coming from those screws; there is no fuel anywhere near them.
Gas migrates like crazy and it's really difficult to see where it's coming from. In your case, it's most likely the slotted plug shown in you first image, but you may as well do 'em all and be done with it.
Take the throttle body off so you can get to the accel pump valves. Take those, the two brass plugs you can see in your images and the jet cover bolt and Cu washer off, dry everything, put 'em back in carefully. Use a scribe to pick up a drop of green (wicking) Loctite off a plastic bag where you squirted some, and touch it to both sides of the crush washers and the threads of that little plug. Give it overnight to set.

[Barry Shay]

After I rebuilt the Zeniths on my 356 C Cabriolet about 30 years ago, I noticed that the right carb was leaking gas. After much work and advice at the time, which included checking all the obvious places like gaskets, screws, plugs, etc., I determined that the gas was actually seeping through the bowl of the carburetor. I actually pulled the carb and poured gas into the bowl and the seepage was obvious. At that time the cost of a new carb was prohibitive, so I bought a pair of Webers (40DCNF) for about $250 and have been using them ever since. Now that the car is worth more than I ever imagined, the experts tell me to reinstall the original Zeniths after getting them rebuilt by Carb Rescue. I'm thinking about it.

[David Jones]

Mark, the most common source of seepage on Zeniths is actually from the jet cover. Sometimes just a new "O" ring will fix it but often with some covers they are distorted and will never seal fully.

[Jeffrey Leeds]

Unless you are planning to sell the car next week, Barry, why mess with the Weber's if they are working fine for you.

Get the Zenith's when you find a good price, have them rebuilt and put them in a box to be included in the sale when the time comes. If the prospective buyer wants a "correct" car you, or he, can make the swap then. On the other hand, maybe your buyer will want to leave the car alone when he discovers how well it's running with the Webers.

Jeff

[Mark Yarrish]

The fuel is not coming from those screws; there is no fuel anywhere near them.
Gas migrates like crazy and it's really difficult to see where it's coming from. In your case, it's most likely the slotted plug shown in you first image, but you may as well do 'em all and be done with it.
Take the throttle body off so you can get to the accel pump valves. Take those, the two brass plugs you can see in your images and the jet cover bolt and Cu washer off, dry everything, put 'em back in carefully. Use a scribe to pick up a drop of green (wicking) Loctite off a plastic bag where you squirted some, and touch it to both sides of the crush washers and the threads of that little plug. Give it overnight to set.

Ron, thanks. Just so I am following you. I should put a little loc tite on all of the brass plug threads 2 on the bottom of the body and two on the side, ( one being the plug for use in setting the float level), should you choose to set the float that way?

Thanks!
Mark

[Heidi Frances]

Hi Mark,

I have the same exact problem! I was just going to start a thread!

Ok, see if this sounds familiar... It is just at the seam between the carb body and the throttle body base. Happens only while the car is sitting cooling off or cool, and is very hard to localize. My car ('58) it is the left carb. The right one seems just fine. I ran the engine and got both carbs full. I then left the fuel on (I never do this regularly) overnight. In the morning bad gas smell, not really and drips, just weeping. I pulled the left carb and carefully and set it on a clean blue roll towel on the bench. I then used brake cleaner and the air compressor to clean and dry everything carefully. I then took pieces of roll towel and folded them and stuck them under and around all the various plugs. I waited 45 min or so and I think I found where it is all coming from - not the plugs... All were dry, but the throttle shaft was soaked Opposite side of the lever and pump). I looked down the throats and both butterflies are soaked. That is after now about six hours or so in our Colorado dry air - they should be bone dry. I went and had a look at the right carb that is still on the car and the butterflies are dry.

Now, the why... Why is the carb leaking, on the bench (so no fuel line supplying fuel, just full a full bowl)? Why is there fuel weeping down through the throats? They are both pretty wet. The fuel is then pooling on the butterflies and then weeping out the throttle shaft.

So, Why is there fuel on the butterflies? Where is it coming from? Is the throttle shaft just too worn?

This is driving me nuts! I have been through this carb a hundred times and I just replaced the carb body. I am starting to think the throttle body is too worn, but I would think that gas would seep through a tight one unless there are some rubber seals somewhere, but I don't think there are on these Zeniths.

Any insight from the carb Gurus? I'll go study the schematics for the body to see just where gas could possible be escaping from the bowl into the throats while on the bench.

Oh, the car runs just fine from Idle to 4Krpm. Solid and smooth... My money is on worn throttle shafts.

Thoughts?

Thanks for posting this!

Franny

[Jeffrey Leeds]

Mark, Ron is suggesting to use Green Loctite. I believe the Locktite number is 290 and it is for wicking purposes (it's also strong). Regular Blue and Red Loctite does not wick as proficiently as does the Green.

Jeff

Edit: To correct Loctite number

[Bruce Smith]

Franny,

This sounds like a puzzler from the Car Talk guys. I'll take a crack at it - what have I got to lose. Assuming that you have no seepage upwards from outside of the throats, gas must be coming from the top. If you checked the float level and it's OK, the accelerator pump squirters seem the other logical explanation. The pump cylinder is ported to the float bowl about 1/3 the way up and again at the top to overflow back to the bowl. Assuming that they're clear (and your float level isn't high), you might be drawing too much volume into the accelerator pump. Have you checked the pump volume (0.25cc/2 strokes)? If the pump rod is set too short, you may have excess gas in the circuit which drips from the squirters.

A simpler possibility might be a leaking float valve, which you may not notice while driving but it is overfilling the carbs when setting.

- Bruce

[Bruce Smith]

Mark -

I agree with Ron on this one, based on your pics it looks like it is the slotted plug. But seeping gas migrates. Before using any Locktite, I'd inspect the sealing washer, the plug, and the carb body to try to find a small scratch, defect, lip, etc. This would be the source of your problem. Rather than Loctite it, fix the source by filing, replacing, etc. That would be a more permanent fix that you won't have to revisit anytime you remove the plug.

- Bruce

[Ron LaDow]

Mark,
Jeff's got it; the green is designed to wick into very tight places, and you want to use it in metal-to-metal joints. Like both sides of crush washers or threads if the plug is to seal by threads only. Every where those conditions apply.
David brings up the jet cover and that is correct, but you also must make sure that the bolt is square to the sealing surface. If not, the copper crush washer will be angled and WILL leak. The boss with the female threads can be pushed back square in a vice with flat jaws, but the carb must be disassembled.

Franny, howdy! Long time, no electrons!
The only way fuel gets in the barrels is a high float level, period. There is no other path at all. The throttle shafts have no effect on it.

Bruce, the A/P nozzles are above the float level, too.

[Heidi Frances]

Thanks Ron and Bruce! and Mark, sorry for jumping into your thread. I'm hoping our issues are one in the same or super related.

Ron: That what what I needed to hear. I don't know all the inner capillaries and such that provide fuel. I will check the float level again, but sitting on the bench and with no fuel attachment, it still seems to be all wet on the inside... I think I'll clean and dry everything on the inside next and see if it will weep on the bench (it shouldn't).

I did replace the body, but none of the internals and such - I just moved them over from the last body. I did find that those little silver caps towards the bottom leaked on both bodies. I cleaned out the little well they sit in from the inside and mixed up some JB-Weld. That solved that leak. They are now bone dry on the outside.

Thanks again, and great to hear from you

Franny

[Mark Yarrish]

Hi Mark,

I have the same exact problem! I was just going to start a thread!

Ok, see if this sounds familiar... It is just at the seam between the carb body and the throttle body base. Happens only while the car is sitting cooling off or cool, and is very hard to localize. My car ('58) it is the left carb. The right one seems just fine. I ran the engine and got both carbs full. I then left the fuel on (I never do this regularly) overnight. In the morning bad gas smell, not really and drips, just weeping. I pulled the left carb and carefully and set it on a clean blue roll towel on the bench. I then used brake cleaner and the air compressor to clean and dry everything carefully. I then took pieces of roll towel and folded them and stuck them under and around all the various plugs. I waited 45 min or so and I think I found where it is all coming from - not the plugs... All were dry, but the throttle shaft was soaked Opposite side of the lever and pump). I looked down the throats and both butterflies are soaked. That is after now about six hours or so in our Colorado dry air - they should be bone dry. I went and had a look at the right carb that is still on the car and the butterflies are dry.

Now, the why... Why is the carb leaking, on the bench (so no fuel line supplying fuel, just full a full bowl)? Why is there fuel weeping down through the throats? They are both pretty wet. The fuel is then pooling on the butterflies and then weeping out the throttle shaft.

So, Why is there fuel on the butterflies? Where is it coming from? Is the throttle shaft just too worn?

This is driving me nuts! I have been through this carb a hundred times and I just replaced the carb body. I am starting to think the throttle body is too worn, but I would think that gas would seep through a tight one unless there are some rubber seals somewhere, but I don't think there are on these Zeniths.

Any insight from the carb Gurus? I'll go study the schematics for the body to see just where gas could possible be escaping from the bowl into the throats while on the bench.

Oh, the car runs just fine from Idle to 4Krpm. Solid and smooth... My money is on worn throttle shafts.

Thoughts?

Thanks for posting this!

Franny

Franny, I think we may have met before, do you frequent the Lafayette Cars & Coffee?

Anyway, yes, I too just want to get this fixed. Sounds like we have the same problem. Not a big enough for a drip, but its fuel so we have to fix it! My car drives great with this too!

Sounds like we are close with some options to try. I will look at my throats when I get home. My pictures were taken this morning with a full carb bowls sitting overnight. It amazes me that the fuel just seeps out with no fuel pressure!

Mark

[Mark Yarrish]

Mark -

I agree with Ron on this one, based on your pics it looks like it is the slotted plug. But seeping gas migrates. Before using any Locktite, I'd inspect the sealing washer, the plug, and the carb body to try to find a small scratch, defect, lip, etc. This would be the source of your problem. Rather than Loctite it, fix the source by filing, replacing, etc. That would be a more permanent fix that you won't have to revisit anytime you remove the plug.

- Bruce

Bruce, thanks. Yes, my goal is to try not to loctite this thing up into one solid piece of metal... although if it didn't leak anymore...

[Mark Yarrish]

Thanks Ron and Bruce! and Mark, sorry for jumping into your thread. I'm hoping our issues are one in the same or super related.

Ron: That what what I needed to hear. I don't know all the inner capillaries and such that provide fuel. I will check the float level again, but sitting on the bench and with no fuel attachment, it still seems to be all wet on the inside... I think I'll clean and dry everything on the inside next and see if it will weep on the bench (it shouldn't).

I did replace the body, but none of the internals and such - I just moved them over from the last body. I did find that those little silver caps towards the bottom leaked on both bodies. I cleaned out the little well they sit in from the inside and mixed up some JB-Weld. That solved that leak. They are now bone dry on the outside.

Thanks again, and great to hear from you

Franny

Franny, I am glad this discussion is helping out another, and not just taking up bits and bytes in cyberspace!

Thanks to all who have helped in the discussion.

~Mark