Fuel dripping onto butterfly after shut off/occasional intake fireball on warm up

[TheBirdistheWord]

Weber 38/38 once warm it has a solid idle and runs relatively well. 

 

I had noticed a "fluid moving around" sound after shut off months ago but assumed it was coolant.

 

I've played with ignition timing and a LOT of air mixture screw fiddling to no avail as far as mitigating the backfire.  Just noticed the extra fuel dropping into the manifold immediately after shut off while doing some tinkering yesterday. Figure they're likely related.

 

Anyone have any insight on what might need attention?  

[datzenmike]

The float chamber is over filling and flooding. This could be...

 

Float out of adjustment. Set higher.

Some floats are hollow. If it leaks it will fill and won't float properly and shut of the fuel into the chamber.

Webers are sensitive to too much fuel pressure, and old ones are even worse. You may need a fuel pressure regulator

 

Backfire through carburetor...

 

Caused by a cold engine not being able to fully vaporize the gas and it runs lean. Called a 'lean backfire.' This is what the choke is for. It forces a rich condition so enough gas evaporates for it to run properly. If you don't have a choke... get one. If you have a choke set it richer or if manual leave on longer till warmed up.

[TheBirdistheWord]

8 hours ago, datzenmike said:

The float chamber is over filling and flooding. This could be...

 

Float out of adjustment. Set higher.

Some floats are hollow. If it leaks it will fill and won't float properly and shut of the fuel into the chamber.

Webers are sensitive to too much fuel pressure, and old ones are even worse. You may need a fuel pressure regulator

 

Backfire through carburetor...

 

Caused by a cold engine not being able to fully vaporize the gas and it runs lean. Called a 'lean backfire.' This is what the choke is for. It forces a rich condition so enough gas evaporates for it to run properly. If you don't have a choke... get one. If you have a choke set it richer or if manual leave on longer till warmed up.

 

According to the fuel pressure gauge it's at 3psi all of the time. Does anyone know stock float level for a 38 outlaw?  Or can I get away with eyeballing it and getting the resting float level parallel with the bowl mounting surface?

 

Could this issue possibly affect A/F screw mixture behavior?  I've never been able to get the same kind of clear adjustment feedback I was able to get with the 32/36 that it replaced.

 

I do have a manual choke, but have been having issues with the cable since the mounting location is different than the 32/36.  Are there any sources for custom length cables? I emailed a few distributors as well as redline directly to no avail. 

[banzai510(hainz)]

I had a tear in the accel pump diaphrame on the side and when ones pushes the gas pedal gas would sqeeze out the diaphrame plunger dripping on the manifold. Thus causeing a big stink inside cab

[Stoffregen Motorsports]

The float should be level when you hold the lid upside down, and just before it depresses the ball on the needle and seat. Basically, with the float level, the needle is closed and you should not be able to blow air into the fuel inlet.

[datzenmike]

One other cause is a bit of debris (dirt) caught in the inlet needle valve preventing it closing all the way.

[Stoffregen Motorsports]

For some reason, needle and seat valves seem to stick more frequently with our new gasoline. Try smacking the carb lid with the plastic end of a screwdriver next time it happens and see if the drip goes away.

[TheBirdistheWord]

Thank you to everyone who has replied.  

 

So it seems like a couple of tap sessions dislodged whatever it was in the needle valve.

 

Today I was coming home from a local meet and with the engine completely warmed up... In fact running a little warmer than usual and I got a carb backfire when I blipped the throttle for a downshift.  I kept driving to see if I could re-create it to try and diagnose.   It happened two more times in about 10 miles but I didn't notice any consistency.

 

What can cause this on a warm engine

[datzenmike]

Backfire through the carb? How do you know it was the carburetor as you can't see this when driving? Not saying it can't be, just how sure are you?

 

Through the carb is usually caused a sudden lean mixture. Could also be a tight valve clearance.

[TheBirdistheWord]

3 hours ago, datzenmike said:

Backfire through the carb? How do you know it was the carburetor as you can't see this when driving? Not saying it can't be, just how sure are you?

 

Through the carb is usually caused a sudden lean mixture. Could also be a tight valve clearance.

 

Other than the fact that it sounds and feels like it's happening right in front of me as opposed to a few feet behind me is really my only "proof" so to speak of intake vs exhaust backfire. Sounds like all of the other backfires that I mentioned earlier in this post

[datzenmike]

Good enough.

 

Inspect the rotor, cap and wires.  I guess it's possible that a spark is jumping to another wire. If clipped to a loom separate them and see it that fixes it.