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Old 05-11-2020, 12:03 PM
Sculldog1 Sculldog1 is offline
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Carb leaking when running after spring startup

Hello everyone, I am having the trouble of gas leaking from the carburetor. After replacing the head gaskets, cleaning the water jacket, replacing a freeze out plug that corrosion on the block had allowed to fall out I finally got the motor fired up. Trouble is I now have gasoline leaking from the carb. It doesn't leak with the engine off and fuel line open but does once I start the engine. I have removed the carb with the flame arrestor attached and wondering where to go from here as to diagnosing what all could be my problem and best course of action. Any ideas?

The motor ran well last season, was winterized properly and had no fuel issues in the two years I have owned it. Thanks

Last edited by Sculldog1; 05-11-2020 at 12:05 PM. Reason: Add info
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Old 05-11-2020, 12:48 PM
JOHN COOKSON JOHN COOKSON is online now
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Check to see if the scavenge tube from the bottom of the carb to the manifold to open and working properly.
The engine not only starts but does it run normally once it starts? Could not tell from the first post if this is true or not.

ex TRUE GRIT

Edit: Check to see if there is a hole in the float(s).

Last edited by JOHN COOKSON; 05-11-2020 at 01:05 PM.
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Old 05-11-2020, 01:40 PM
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I guess you have already seen it, but just in case..
https://www.youtube.com/watch?time_c...ature=emb_logo
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Old 05-11-2020, 02:31 PM
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Thanks for the reply folks. It seemed to run normally (as near as I could tell as I was running with the intake water line into a bucket with the hose filling at the same rate the rwc was taking the h2o). The engine ran fine as I shut the choke down and increased/decreased throttle. Just had a pretty steady dripping coming from carb. It did take a bit more cranking to fire her up the first time though.
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Old 05-12-2020, 02:38 AM
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Can you tell where the leak is exactly emanating from on the carburetor?

Last edited by Ando; 05-12-2020 at 03:17 AM.
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Old 05-12-2020, 10:56 AM
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Sounds like the float valve isn't closing. I'd replace the float valve. While you've got it open, check the float. Liquid in it? Does it bubble if you put it in hot water?
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Old 05-12-2020, 10:57 AM
JOHN COOKSON JOHN COOKSON is online now
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Quote:
Originally Posted by Ando View Post
Can you tell where the leak is exactly emanating from on the carburetor?
Was gas pooling in the throat (as I assumed in post #2) or leaking around the outside of the carb?
If gas was leaking around the outside of the carb then the gasket between the two carb halves has failed.

ex TRUE GRIT
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Old 05-12-2020, 11:21 AM
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Answers?

Does it drip while running or stopped or both?

I have not seen the question regarding the scavenge tube being hooked up, is it?

In order for it to leak from where the body halves come together the bowl would need to be full IE a faulty needle & seat.

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Old 05-12-2020, 01:10 PM
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Quote:
Originally Posted by Sculldog1 View Post
...Trouble is I now have gasoline leaking from the carb. It doesn't leak with the engine off and fuel line open but does once I start the engine. ...
This is usually indicative of the float valve not closing. The fuel pump continues to pump fuel until the float bowl overflows. Common causes are:
  1. Crud in the float valve seat
  2. Float valve stuck
  3. Float body has a leak and has taken on some gas.

Disassemble the carb and check that the float valve operates freely and the tip and seat are clean.

Check the float body for leaks. Simplest test is to shake it next to your ear and listen for sloshing. A more sensitive test is to balance it on a knife-edge, with one float lobe on each side. If one lobe has flooded, it will balance way off center.
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Old 05-15-2020, 12:05 PM
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Thanks to all.

I have gotten to the bottom of my troubles. Indeed the float valve was getting stuck open and overflowing. Once I took it apart and saw a bunch of black bits and sediment and cleaned the jets everything working fine. I looked inside mechanical fuel pump on hunch that trouble was coming from it. Sure enough the diaphragm was giving up the ghost in the form of little bits of rubber flaking off the fabric that reinforces it. Sediment screen very clogged and the sediment bowl gasket washer disintegrated as soon as bowl was removed. Got the rebuild kit and all is well! Thanks again to everyone.
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Old 05-15-2020, 05:04 PM
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Sculldog1--

Thanks for letting us know the answer and resolution of your problem. Often it seem like a thread is progressing... and then goes suddenly silent.

It's like working through a good book, only to discover your copy is missing the final chapter. ;^)
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Old 05-15-2020, 06:36 PM
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Congratulations on chasing down the problem. The question remains, what caused the diaphragm to disintegrate? I suspect the previous use of ethanol fuel, which IMO degrades rubber. Adding MMO to the fuel will also help preserve the diaphragm and the bowl gasket. I think if you use non-ethanol with MMO in a rebuilt pump, that problem won't happen again.
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Sculldog1 (05-18-2020)
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Old 05-18-2020, 09:18 PM
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I agree that Ethanol is no good.

The diaphragm looked like it was more of a dry rot kind of deterioration as the bits of rubber were kind of brittle and breaking off where the flexing seemed to be hapenning. The gasket on the sediment bowl appeared to be an ethanol casualty as if was very gummy and generally gooey which is what heppens to small engine lines in my experience. I will be making the extra effort to get non-ethanol fuel exclusively in the future.
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Old 05-19-2020, 09:58 AM
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I ran E-gas here in So Cal for as long as it was available. I sold the boat with the same "mechanical pump" rebuilt around 2005 or so after running it for 15 + years. I doubt the ethanol was bothering the diaphragm as it was probably very very old. The mechanical pumps are far more durable and safer to operate than an electric, also simpler .

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