Float/needle valve stuck shut?

[Bob N]

Don,

When I launched my boat this week, my engine would not start. I confirmed that I had spark (especially after I tried starting fluid spray and the engine would run for a few seconds). I used my trusty jumper wire across the oil safety switch and found that the fuel pump was working fine--fuel pumped out after I removed the fuel hose from the carb. When I opened the main passage plug on the carb, no gas came out. My conclusion was that somehow the float valve was stuck shut and was not letting fuel into the carb.

Today I removed the carb to clean it. When I first took it off the engine, I shook it gently and could not hear a rattle from the float. Of course, in the process of opening up the carb, the needle--if it WAS stuck--came unstuck. When I examined the needle (unfortunately, I did not have a magnifying glass), I thought I saw an impression in the rubber coating as though it had been stuck to the seat. I replaced the needle and cleaned the carb. When I cleaned it, the first thing I did was to spray a bit of cleaner through the gas inlet. It flowed out the needle seat, so I don't think the inlet passage was clogged. When I got things back together, it started on the first push of the starter button.

Question: I ran the carb dry when I winterized the boat--how is it possible that the needle could stick shut in its seat? Could ethanol in the gas have softened the rubber coating on the needle, causing it to glue itself shut over the winter? By the way, the carb is about 6 seasons old and I have not cleaned it before today.

I am happy that the engine is now running fine, but remain puzzled.

--Bob

[Don Moyer]

Bob,

We have heard of at least one or two stuck float valves each year that we've been in business. Yours is the first so far during this 2007 spring start-up season. To this point, the occurrences of stuck float valves seem to be rather consistent and within the small margin of a few expected random episodes each year, so I have no reason to believe that Ethanol fuel is involved.

I don't know what (if any) fuel additives you may be using, but I would not be surprised if limiting the use of additives in the fuel to only the recommended dosage of Marvel Mystery Oil may minimize exposure to sticky needle valves.

Don

[Bob N]

I've been using MMO and a fuel stabilizer. I'm concerned about not using the stabilizer, since I only run the engine a total of a few hours a month. I realize that manufacturers ads are not the best source of info, but the latest Boat US magazine has an ad for Starbrite's "Star Tron" that supposedly burns completely in the combustion process and at the same time prevents phase separation of the fuel sitting in the tank. Any thoughts? Thanks.

--Bob

[Don Moyer]

Bob,

My usual fallback position on all additives is that if a particular additive is working for you, then by all means continue to use it. If you have annoying symptoms that might be caused by an additive, then you could discontinue its use long enough to see if the symptoms go away. In your case, I still believe that your stuck float valve was probably a random occurrence.

Don

[Bob N]

Thanks for your advice

Went down to the boat today and took her out for a short spin. Everything is fine. Thanks.

--Bob

[Bob N]

Problem has returned

Don,

My engine has been running perfectly ( well as perfectly as a 37-year old engine probably could) all season, since I replaced the carb float needle in May. Today I experienced the same symptons that I did last fall--which led to the stuck needle problem: After motoring for a bout an hour, I throttled back and ran dead slow to enter the slip. Then, as we were tying up, I let the engine idle. After a few minutes it stalled and would not restart. The fuel pump worked fine when I used a jumper wire and I checked to see that I had spark. I did not have time to do any further checks. For a start, I'll open up the passage plug to see if there is gas in the carb. I suspect the new needle is stuck. I notice in the forum that other folks have had a similar problem. Is a needle available without the rubber coatling at the tip? I suspect that it is getting gummed up--possibly because of the ethanol in the gas.

--Bob Nash

[Don Moyer]

Bob,

We're always ready to accept new information, but to this point (thankfully) we have no documented evidence that I know of where 10% Ethanol has had any debilitating effect on the tip of the needle in a float valve.

Don

[rshearley]

Needle valve degraded?

I have had a similar problem with the float needle valve.
The rubber tip in mine appeared to have worn/degraded after basically hardly any use.
This had led to fuel leaking through the flame arrestor.
I noticed the rubber tip seems to be a newer modification to the needle. Can you re-use the old needle valve with the newer seat?
I have a spare engine for parts and ended up switching carbs but can't get the engine to start now so I will have to work on the original carb which I rebuilt last year.
I had cleaned the entire assembly with carb cleaner prior to putting it back together. Perhaps this is the culprit. The rubber actually had what appeared to be threads pulling off it. I doubt it was the alcohol in the fuel but I suppose anything is possible.

Rich Shearley

[Sony2000]

Last week the float bowl was dry, but the gas would not flow in. A stuck float needle with the 1/2 carb in my hands and the float hanging down, the needle stayed up. I used carb cleaner. Back in the boat and the needle refused to drop and let gas into the float. So rather than wait a week for a replacement, I chose two Dremel bits to lightly resurface the brass seat. A rough ball bit and another pointed bit, both to polish the brass seat. The old float needle now drops from its shaft. Tomorrow, I'll try it on the engine.