Gas in the air intake box

**Peter** · #1 (**permalink**) 11-01-2009, 02:31 PM

What a wonderful weekend it was....sunshine, mid 70's, absolutely perfect to take the Spider out. On the way home, she started running a little rough, sputtering on acceleration....but not a problem to rev here once going, so I did not feel it was fuel starvation...some backfiring too...too much fuel? I came home, and opened the hood. Noticed fuel had dripped on top of the fuel filter, it had come from the little drain holes in bottom of the air intake. Took the cover off, not a whole lot of fuel in there, but I could feel the carb intakes being wet, at least the one I checked.....not sure if this is related to poor performance......any idea what this could be? Does this sound like a carb rebuild to you?

**Tifosi** · #2 (**permalink**) 11-01-2009, 03:58 PM

Reminicent of a stuck/sunk float, fouled float needle seat, or overpressure from the fuel pump, but I'd wait for others more familiar with them carbs to offer more betterer ideas.

**alfaparticle** · #3 (**permalink**) 11-01-2009, 05:36 PM

How wet? My Webers have always had a thin film of gas in the intakes. I have to open the throttle to start a hot motor. Otherwise it has no noticable effect on performance.

**Peter** · #4 (**permalink**) 11-04-2009, 07:36 AM

Quote:

Originally Posted by alfaparticle

How wet? My Webers have always had a thin film of gas in the intakes. I have to open the throttle to start a hot motor. Otherwise it has no noticable effect on performance.

**60sRacer** · #5 (**permalink**) 11-04-2009, 08:16 AM

If the float in one of the carbs sticks or is misadjusted, or if the fuel pressure is too high (3-4 psi is all that the needle can handle), the carb will overflow. The carb vent/overflow is into the air box - its that big hole at the top of the carb.

Take the fuel cover off - the round cap with thumbscrew - and measure the fuel level (procedure in the book).

Robert

**Andrew** · #6 (**permalink**) 11-04-2009, 08:27 AM

My Weber airbox always has some residual fuel in it; isn't there normally a "standoff" cloud of air/fuel floating outboard of the throats, some of which will deposit inside the box?

Andrew

**Peter** · #7 (**permalink**) 11-04-2009, 08:46 AM

I'll open it up and check it out....got Dellorto's on her BTW. The fact that she's not running right AND I see fuel dripping tells me something's not quite right

**msiert** · #8 (**permalink**) 11-04-2009, 09:58 PM

My setup is a little different with fuel injected individual throttle body's but I had the same symptoms with gas in the airbox and poor running when my fuel pressure regulator was crapping out.

**Peter** · #9 (**permalink**) 11-08-2009, 12:20 PM

Thanks for all the suggestions so far!! The fuel pump is an electric, Facet I believe, low pressure pump for carbs that I've had for years, so I don't think all of a sudden it developed more pressure. I don't have a pressure regulator installed, but I have one laying around that I could try. As I don't think this is the issue, I dug into the carbs. i noticed that I forgot to connect the choke cable lat time I installed them

but that should not cause the issue, I would think....don't need the choke anyways.
I took to tops of the carbs off, and the floats look fine, no leaks. With my rudimentary testing methods of simply blowing air through the fuel line and lifting the floats, I seem to have established that they work as intended. Next thing I noticed is that the was a lot more fuel in the bowls of the front carb, closest to the fuel filter. See picture...it's hard to see but I gues the level in the front carb was probably close to 0.5" higher....I looked at the floats again to see if one closed the valve sooner when lifting the float, but without any proper testing techniques, I could not see a difference. The both look very similar too.
Anyone have an idea how/what to test next? BTW, these are Dellorto carbs

180OUT · #10 (**permalink**) 11-08-2009, 01:01 PM

Quote:

What a wonderful weekend it was....sunshine, mid 70's, absolutely perfect to take the Spider out. On the way home, she started running a little rough, sputtering on acceleration....but not a problem to rev here once going, so I did not feel it was fuel starvation...some backfiring too...too much fuel? I came home, and opened the hood. Noticed fuel had dripped on top of the fuel filter, it had come from the little drain holes in bottom of the air intake. Took the cover off, not a whole lot of fuel in there, but I could feel the carb intakes being wet, at least the one I checked.....not sure if this is related to poor performance......any idea what this could be? Does this sound like a carb rebuild to you?

**radamm** · #11 (**permalink**) 11-08-2009, 05:20 PM

Sometimes a float chamber will"empty" due to a plugged air bleed. The air bleed is there to prevent a siphoning action of the carb's fuel circuits. A restricted bleed will have an effect on the mixture usually during intermediate throttle settings. Backfiring can be a symptom of a lean mixture caused by a restricted air bleed. Since you have the tops off I would use some carb spray in all accessible jets, bleeds, and other openings followed by a blast of compressed air to clean the circuits. Be prepared for splatter. I hope this helps.