Why does my carb flood?

[Chris1956]

I have a '93 Merc 135V6. The lower carb seems to flood, althought the float is set correctly and the inlet needle seams to seal very well. Is it possible that the mid or upper carb are actually flooding and the fuel travels thru the intake manifold, recirculation hose or some other path, making it appear that the lower carb is flooding?

 

[Frank Acampora]

Re: Why does my carb flood?

If you have a starting enrichment solenoid instead of a choke, and if it is leaking, or partially manually turned to the start position the bottom carb being the lowest will preferentially get the extra fuel. That might do it.

 

[Chris1956]

Re: Why does my carb flood?

Frank, Thanks, but I checked that, and it doesn't leak.

 

[Laddies]

Re: Why does my carb flood?

Chris, years ago we used to have a lot of problems with V/6 carbs leaking and a factory rep told us to make a simple tool to ck carbs for dripping on a V/6, take a short piece of fuel line put a male hose end on it, a pressure gauge if have one on a tee fitting, before assembling the bowl to the carb and the floats set, hook the line you have made to the fuel fitting on the bowl and a fuel tank pump the system up with the primer bulb to 10 lbs. the fuel level in the bowl should not go above the inside ledge on the float bowl if it does cheat the float till it holds or replace the needle as it's no good. We use it on most carbs today to ck for leakage before installing them on engines. Hope this helps--Bob

 

[Texasmark]

Re: Why does my carb flood?

Both you guys touched on what I would have suggested. For it to travel down the inside of the intake mfld seems very far fetched. It's not leaking from somewhere else and running down onto and then dripping from the lower one is it?

When you say it floods, I assume you mean that when you tilt the engine fuel comes out the throat of the carb.

When you say the float system works ok on that carb, how do you know?

Have you held the float parallel to the carb casting with the primer bulb squeezed firm and minimal fingertip pressure on the float with no leaking?

Is the seat on the needle rubber or metal?

You aren't running an electric fuel pump are you?

Mark

 

[Chris1956]

Re: Why does my carb flood?

Thanks for all the good ideas. As it turns out, the outer diaphram of the fuel pump leaks. Fuel poured out of the throttle plate when I tilted the motor up a bit.
Thanks for the attention...

 

[Silvertip]

Re: Why does my carb flood?

Leave it to the factory to come up with a complicated way of testing inlet needle function. When rebuilding a carb, before buttoning it up, invert it and simply blow into the inlet fitting. If air passes, you screwed up. If not, button it up. After installation, slip a piece of fuel line on the inlet fitting and again blow into it. If you can't pass air (into the inlet wise guy) the seal is good. If air passes, it's leaking and you get to do it over again.

 

[Chris1956]

Re: Why does my carb flood?

Actually I did the "blow into the fuel inlet with the carb inverted" trick. The inlet nedle functioned perfectly, during all tests. After I took the carb off for the third time, I even put the float into some water to see if it would sink.

My only miscalculation was not thinking the hole in fuel pump diapham would allow the fuel to pour out of the throttle plate. I thought the reeds would trap the fuel in the crankcase,

 

[gonelong]

Re: Why does my carb flood?

Leave it to the factory to come up with a complicated way of testing inlet needle function. When rebuilding a carb, before buttoning it up, invert it and simply blow into the inlet fitting. If air passes, you screwed up. If not, button it up. After installation, slip a piece of fuel line on the inlet fitting and again blow into it. If you can't pass air (into the inlet wise guy) the seal is good. If air passes, it's leaking and you get to do it over again.

Exactly how I determined if my inlet needles were sealing. I did this before and after adjusting the floats so I had a frame of reference.

GL