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Old 08-26-2020, 09:42 PM
JackConnick JackConnick is offline
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Leaking Carb

Arrgh.

My carb seems to be leaking gas. After servicing it now 3 times and checking the float, replacing the needle valve and seat, it's still leaking.

Frustrating, as otherwise it runs perfectly.

I replaced the scavenging tube, thinking that was the source, also the needle valve, seat and gasket. All the usual seats, etc. cleaned/replaced.

I called MM and talked to Ken, he said to double check that the float was sitting perfectly level with housing when turned over. I checked it and made sure that they seemed to be square and level.

So it seems that the only solution is a $295 new carb. (?) I leave Labor Day weekend for 2 weeks and it's too dangerous to screw around with.

But it ticks me off, as it's probably just a small adjustment somewhere.

Seems like a very poor and dangerous design, IMHO. From now on, I'm turning off and running the system out of gas. I've had a couple of scary times coming down to the boat and finding pooled gas. I service the carb about every 100 or so hours.

Jack
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Old 08-26-2020, 10:30 PM
Dave Neptune Dave Neptune is online now
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Do you have any idea where the fuel is leaking from? Unless it is the needle and seat of which you changed out something should of changed. Unless there is a crack that is about all that will leak other than a plug which is an external leak.

One possibility is a hole in a float but then the fuel will usually run out as fast as the pump pumps.

Does it leak while running?

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Old 08-27-2020, 12:40 AM
JackConnick JackConnick is offline
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It looks to be running out the main gasket. The floats appear to be ok, didn't have any fuel in them, checked twice.

Bone dry while it is running.

Some sort of small crack might be what's going on, but nothing visible.

Jack
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Old 08-27-2020, 01:34 AM
JOHN COOKSON JOHN COOKSON is online now
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Feel around the carb with dry paper towel in your hand when the carb is leaking. You might be able to tell where the leak is this way.

ex TRUE GRIT
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Old 08-27-2020, 01:39 AM
JackConnick JackConnick is offline
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Yeah, did that, it's on all sides slightly and leaking down. There's not a single point.

Jack
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Old 08-27-2020, 08:03 AM
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The carb may have become warped. Someone on here may have a method to fix that so it seals again.
I had a troublesome carb and eventually just got a new one from Moyer and it has run perfect ever since. Also I turn my fuel pump off and run the engine out of gas when done for the day.
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Old 08-27-2020, 09:45 AM
Dave Neptune Dave Neptune is online now
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If fuel is leaking out around the main gasket then the needle & seat assembly is compromised somewhere. In order for fuel to leak out of the main gasket the fuel bowl has to be to full. In normal operation the bowl's fuel level is kept at about 1/2 bowl well below the gasket. That means that fuel is getting by when the float is holding the needle in the closed position. You also state that the carb stays dry when running.

There has to be some sort of gap either in the seat, the seats gasket or the seat itself or the needle's point has a minor flaw. Once shut off if your fuel level in the tank is higher than the carb gravity will prevail and the fuel will slowly leak by and once the engine is running the "leak" is moot as the carb uses far more than the leak can leak.

Take another close look at the needle and seat assembly with a magnifying glass of some kind.


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Old 08-27-2020, 12:10 PM
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Since you've replaced the float needle & seat, I'm still suspicious of the float itself, even though you've checked it. Maybe it got bent during reassembly? A new one is only $21:

https://moyermarine.com/product/carb...at-fcar_02_54/

A lot cheaper than a new carb if it works! And a useful spare even if it doesn't.

A float is one of the things I keep in the "critical items I can't kludge" spares kit that I keep aboard when I'm cruising.
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Old 08-27-2020, 12:49 PM
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New Carb

My carb was doing the same thing. I just bought a new carb from Moyer and it’s fixed. One less thing to fiddle with. DVD
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Old 08-27-2020, 02:51 PM
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Just went through the fuel leak thing with my chipper/shredder - Tecumseh H35 was leaking fuel out of the carb. Went through it twice looking for the leak - no good. Finally held the float bowl up to the light, found two pin holes in the bottom! Looked like a snake bite - metal dented in slightly with a pin hole in the bottom of each dent. Put some epoxy on it but I don't trust it - parts on order (carb itself is no longer available).
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Old 08-27-2020, 03:18 PM
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Based on Dave's guidance that a leak from the carb main gasket can only come from fuel leaking around the needle seat/float assembly:

Could the needle seat just not be screwed in all the way? I recently had confusion on setting the float parallel by backing out the seat.

Could the needle itself be dropped in upside down? I get turned around every time I put it back together. I'm not sure if you would be able to identify this while running, as it may function well enough when fuel is being sucked through the jets. It would then not make a good seal when shutdown and gravity could cause the bowl to fill up to the main gasket (maybe).

Of course, there could be a fracture somewhere. I think it would have to be in the bowl.

Do you have an electric or mechanical fuel pump? I'm not sure what's inside the electric pumps, but if I understand the mechanical pump correctly fuel shouldn't be able to move through it while shutdown. One of the two valves is always shut, and even if is pressure released through a leak they would both be shut by a spring.

This could also be indicative of a bigger leak in the boat fuel system. Assuming you have a shut off valve immediately downstream of the fuel tank there shouldn't be any fuel leak when shutdown. I know nothing is perfect, but like plugging the top of a straw full of liquid, even removing the carb (creating a large carb leak) should not result in the entire volume of fuel lines leaking out.

-Joe
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Old 08-27-2020, 03:27 PM
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My experience is that beyond a certain point, a new carb will more than pay for itself in time spent NOT screwing with it
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Old 08-27-2020, 11:26 PM
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take the carb drain plug out.

Find out what size pipe fits in the hole. I am guessing it is 1/8 pipe. Get a pipe nipple this size. get a clear hose the will fit over this nipple. Screw the nipple in the carb and run the engine. Hold the hose up so that it will fill to the level in the carb bowl. This will show the level and if it is too high and may be running over the top.
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Old 08-28-2020, 01:29 AM
JackConnick JackConnick is offline
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Thanks for all the great ideas!

Don actually called early this morning and we went over it. He seemed to be sure that it was just dirty fuel through the system.

He told me to use the electric fuel pump to flush the entire system out by jumping the oil pressure safety switch with the ignition on. I have a MM drain plug on the carb that helped, as I just had to crack open the bolt a couple of turns.

Then I just wedged a cottage cheese container with a coffee filter in it, and some pads under it, and ran the fuel pump for about 5 mins at a time to drain out about 8-10 oz of fuel. A glass container would of been nice, but wouldn't fit. A small aluminum tray might actually work well.

I attached a couple of photos. I think it's a neat trick to have in your bag...

The first time it looked like a sand bar! I did 4 drains in all following Don's directions to really flush it well. Each time it got better, finally littler or no grit was spotted.

I emptied the fuel back into the tank through couple of coffee filters and caught a ton of junk.

I drained the main fuel filter and saw just a small bit of grit, not a lot.

I decided to go ahead and change the polishing filter, even though it was only 25 hrs old. When I went to the store, they looked it up and it was a 20 micron filter, not a 10 as Don sells.

I was on a cruise in July and got a tank of gas at a small resort only open in the summer. I'm pretty sure they sold me the dirty gas.

I'll get a new 10 micron filter in the morning. Give it a test run and check later for leaks. Fingers crossed that was the issue.

Hopefully I got most of the junk out of the tank and the new finer filter will catch the rest in the future.

Jack
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Old 08-28-2020, 06:50 AM
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Wow - that is a lot of sand to make it through TWO fuel filters
Note your alligator clips will spark and you are creating an explosive environment. You have to take care to do nothing that makes a spark once you are draining gas and filling the boat with fumes.

I am still puzzled by one thing - if my needle valve sticks open, I can smell gas because it pools in the carb and might even drip out around the flame arrestor connection, but the only time it ever leaked down the sides of the carb from the point the top and bottom halves connect is when the carb was warped and would not seal. I MarineTex-ed it together, which worked until I got home.
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Old 08-29-2020, 10:26 PM
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Quote:
Originally Posted by joe_db View Post
The carb may have become warped. Someone on here may have a method to fix that so it seals again.
I had pretty good luck "machining" the surfaces of both halves with a belt sander. I just held the carb in one hand (one half at a time) and the sander in the other. I had to do some manual sanding around the pivot point where the float is mounted.
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Old 09-04-2020, 01:47 AM
JackConnick JackConnick is offline
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I really thought the dirty fuel was going to solve the leak, but no go. Same symptoms, ran fine, but then gas leaked out the needle valve.

I ended up just ordering a new carb as I was out of time. Installed it tonight and she ran great, actually much smoother, so even using carb cleaner I think the old one had gunk left in it.

But I disassembled the old carb as I'd like to fix it as a spare. Again, no "smoking gun" or dirt, everything looked ok. No missing washers, etc.

However, looking at the float I noticed a shiny spot from the top of the needle valve. I double checked that the seat was down tight. It looks nive and level when installed as well.

Has anyone seen this before?

Should I just buy another float? It's not leaking.

Jack
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Old 09-04-2020, 02:23 AM
JOHN COOKSON JOHN COOKSON is online now
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Quote:
Originally Posted by joe_db View Post
The carb may have become warped. Someone on here may have a method to fix that so it seals again.
.
Hold the two halves of the carb together (no gasket) against a light source. If you can see light through the two halves the carb is warped.
Scratchee in post # 16 washable to fix this condition.

ex TRUE GRIT
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Old 09-04-2020, 10:24 AM
JackConnick JackConnick is offline
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It's not leaking out the halves, gas is just flowing out the throat and anywhere it can get out. The needle valve is leaking.

Jack
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Old 09-04-2020, 11:25 AM
Dave Neptune Dave Neptune is online now
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The "spot" on the float arm is where the needle rides so it is worn smooth as it should be.

A "leaking spot" would be on the chamfer at the bottom of the seat on the inside where the needle sits OR the end of the needle itself is compromised.

The only other way fuel gets by that assembly is through the threads of the seat and/or the "sealing washer" for the seat.

Dave Neptune
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Old 09-05-2020, 01:40 AM
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Yeah I agree. And all are new. I checked for burrs on the seat. All is screwed down tight.

Jack
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Old 09-08-2020, 12:32 PM
Dave Neptune Dave Neptune is online now
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If all is well with the needle and seat then there is only about one way it could leak. I see in the pic I think that you have the fuel line fitting removed. This is a no-no in carb work as it is just unnecessary. On a few occasions I ran across a crack in the housing from "over tightening" the tapered pipe threads. Depending on where the crack was they could leak (bypass) fuel into the bowl bypassing the N&S OR leak down the outside of the carb and there is no fix for that. Your leak has to be between the end of the fuel hose clamp and the bowl.

Just a hair line mark can leak fuel. Did you try dressing the seat? Do you have a black tipped or a solid needle?

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