Leaky carb - the floats

[rigspelt]

After rebuilding the carb on this new-to me A4/boat and running it at the dock for the first time this spring, I could smell a hint of gas. Found and could see a tiny drip with the finger test under the main jet plug. Carefully tweaked it a bit (heeding Don's warning about tightening too much and squishing the hard-to-replace washer thereby causing a worse leak) which stopped that drip.

Couple of days later (still not running engine much, just brief periods at the dock to set up idle and get feel for shifter) I convinced myself I could smell a hint of gas after opening the boat. Finger test found a bit of wet gas on the undersurface of the carb at the flame arrester housing-carb joint. Removed the flame arrester and found 1/4" of fuel in the throat. Most likely scenario is leaking float valve and dripping out the choke linkage, or around the old flame arrester o-ring, but I cannot verify that.

I tossed in the towel tonight and ordered a new carb from MMI to replace this apparently original carb. The linkages and screws are all creaky, and maybe I blew the rebuild, not being a mechanic.

For sharing the learning, here are photos of the floats and valve. For those new to the insides of the carb, it is upside down in these photos: the floats press up as the chamber fills (down in these photos), shutting off fuel from the pump as the stainless float valve needle seats upward into the brass seat.

When I did the rebuild, I had used the dowel in the kit to buff the valve seat. I found no grit in the float valve, but of course it may have come off if one was there. I had tried to make the bottom of the floats horizontal or a hair up. How does the alignment look?

[Marian Claire]

Could gas be leaking around the brass seat? Not snug or maybe too snug and compressing the round gasket. Just thinking out loud. Dan S/V Marian Claire

[sastanley]

Rigs, Does your valve have a rubber tip? It is hard to tell in that photo.?

[lat 64]

Rigs,
It seems to me that it is unsafe just to have only a float valve to hold back the siphon and pressure from the fuel tank when the boat is at the dock.

Do you have a fuel shut-off valve?
I turn off the fuel even if I just go to lunch. Also, I think the proper electric fuel pumps have a check valve sort of thing that will stop this siphon or drip from the tank.
My pump is too strong to leave on if the engine dies, as I found out last month. It needs an oil pressure shut-off switch.

Be safe,
Russell

[joec43]

In my carb (its an old style) there was a little wire that hooked onto the float, and went around the needle valve which forced the needle into the seat.

During my rebuild last summer, I lost the little wire, and now that am home, expect to be looking for another to replace it.

I do not see this wire on your float, so possibly, the needle (I'm sure thats not thee correct name for it, but its the stainless piece that goes up and down into the seat when the float moves up and down) is sticking.

You can see the groove for the wire in the bottom part (not the sharp end) of the needle.

Joe

[rigspelt]

Originally Posted by sastanley

Rigs, Does your valve have a rubber tip? It is hard to tell in that photo?

No, and I looked for that yesterday after I removed the carb and did the research on leaky carbs. I wondered if there was supposed to be one. If there was and I overlooked it in the rebuild kit, that could explain the leak.

http://www.moyermarine.com/forums/showthread.php?p=9971

Originally Posted by lat 64

It seems to me that it is unsafe just to have only a float valve to hold back the siphon and pressure from the fuel tank when the boat is at the dock.

Yes, I do, and use it routinely with this engine. I should have made this important point, so thanks for doing so. As I understand it, the Facet pump model normally used on this engine does not have either an internal check valve or postive shutoff feature, although some do. There are threads where folks have talked about a second postiive shutoff valve just in front of the pump, as well as at the tank.

Originally Posted by Marian Claire

Could gas be leaking around the brass seat? Not snug or maybe too snug and compressing the round gasket. Just thinking out loud. Dan S/V Marian Claire

Another good thought. It looks OK sitting here on my desk. Getting the right feel for bolt or nut tightness is always a pain for us amateurs. Hence my decision to just cut my losses and buy a new, professionally set up carb from MMI.

Originally Posted by joec43

In my carb (its an old style) there was a little wire that hooked onto the float, and went around the needle valve which forced the needle into the seat. ... You can see the groove for the wire in the bottom part (not the sharp end) of the needle.

That's interesting, Joe. I had not seen mention of that wire in any of my sources. Presumably it was not used in later models?

[Don Moyer]

The tiny wire spring clip that was used to attach the needle to the float assembly on some early model carburetors was discontinued by Zenith many years ago. When I asked them about it they said only that the clip caused more problems than it solved.

Don

[Don Moyer]

It looks like your float setting might be a bit on the "droopy" side. I tried to attach a photo of the setting which basically reflects the factory setting on a new Zenith. The setting in your photo would result in a slightly higher float level, leading to a slightly richer mixture. I'm not at all sure however that this condition would explain the fuel collecting in the bottom of your intake throat.

Don

[tenders]

Rigs, the resolution and shadows may be causing this but do you have the pointy side of the needle valve pointed towards the float of the carb? It should be the other way around.

[67c&ccorv]

Rigsy,

In your first pic it looks as if the float needle valve is sitting under the float lever?

- the needle should fit into the middle of the float lever beams by the grove in its uppermost end (opposite the needle). If you set your float level by setting the beams on top of the needle it would give an incorrect level (rich I think?).

That, in addition to the lack of the viton rubber tip on your needle probably caused your fuel leak.

I wonder where that little rubber tip is?

[sastanley]

Russ, I agree with you, but right now I am relying on it (the float/needle valve) to do so.

I am thinking about some other sort of way to turn off my fuel supply when not in the boat. Right now I have to remove the drawer in the galley to get to my tank fittings - I replaced the stock tank with a plastic one..dimensions are close but it is longer and now protrudes out from under the quarterberth into the galley, hence access behind the drawer. Regardless, this is still actually easier than previous access thru the quarterberth panel..there is ALWAYS stuff in the q-berth covering the access hatch.

[rigspelt]

Originally Posted by tenders

Rigs, the resolution and shadows may be causing this but do you have the pointy side of the needle valve pointed towards the float of the carb? It should be the other way around.

No, pointy end was in the seat, blunt end under the float.

Originally Posted by 67c&ccorv

Rigsy, In your first pic it looks as if the float needle valve is sitting under the float lever?

No, it is in the correct position. Same as the photo Don posted today in this thread..

[rigspelt]

I got out a magnifying glass and see that the tip of the float valve needle is indeed covered with a slight film of rubber. So, (1) that was not the issue, and (b) this is what the rubber tip looks like.