fuel draining into carb at shut down and a stumble at about 1/2 throttle

[185StingLX]

I've been dealing with a hot/warm starting issue for some time. If I shut it down just long enough to pull a skier out and then restart (~2 minutes) it starts back up easily. But if I let it sit for more than 10 minutes or so I have to go full throttle to get it to start and I get black smoke from the exhaust. While running on the hose I could hear liquid flowing at shut down. I looked into the carb barrels and they were being filled through the boosters. This ran in for about 5-10 seconds and slowly stopped. My first thought is/was a float or needle/seat issue. But it will idle all day and I have never had an issue in any no-wake zones.

I pulled the float bowl off and set the top of the float even with the top of the bowl and retested. It leaked down again. Lowered the floats about a 1/2 turn and tested with no draining. I thought I had found my answer. But, on the water, the problem reappeared. I am thinking of replacing the needle/seat under the assumption of an intermittent problem.

But, can a stuck power-valve cause the same problem? I am thinking not since the fuel still has to travel higher than the correct fuel level even through the PV.

Part 2:
Since adjusting the floats, I have a bit of a stumble while slowly or moderately throttling up. It also acts a little bit sick while coming off plane if I bring the throttle to about 1/2. This doesn't happen as soon as I throttle down but only after the engine slowly lowers to the new speed. And it only takes a slight increase or a drop back to idle to solve it. I never had any issues with this prior to changing the needle/seat height. How sensitive is the tuning to fuel bowl levels? I expected it to be not very sensitive since there is no good way to check the level with the engine running(plug or sight-glass). I have considered swapping to a float bowl with a sight glass.

PS - The acc pump does give me a nice spray when the throttle is applied.

Thanks for reading... Any help is appreciated.

 

[jeffnick]

Q-jet?

http://www.hotrod.com/articles/hppp-1107-home-remedy-quadrajet-carburetor/

I just covered the plugs with JB Weld.

 

[Scott Danforth]

what type of carb? what motor? what year?

you have multiple issues with the carb. time to pull it off, clean it and go thru it.

 

[185StingLX]

Its a Holley 2B on a 2008 Volvo 3.0 GLP-J. I think its a 2300.

I think a full carb rebuild will happen once I give up on this seasons temps.

I have pulled the fuel bowl and ensured that the jets were clean. I also verified that the acc pump worked. It does respond to idle screw adjustments(after removing those evil caps that Holley/Volvo installed).

 

[G_Hipster]

After sitting 10 minutes sounds like a heat soak/ fuel percolation issue. Not familiar with that engine on how stuff is routed or if the carb can be isolated or the fuel lines wrapped. A bad power valve would be pouring gas down the throats non-stop and be causing lots of flooding and the mixture screws would be unresponsive.. Float height can be very sensitive. Put them back where they were originally. Changing seemed to cause more issues than it's solved. Too low a level you uncover the jets as fuel sloshes around in there creating a lean stumble.. If your running ethanol switch to non-ethanol it's less susceptible to fuel percolation. A carb kit and a couple hours to make sure it's good. Power valves are not always included in kits, but while I was there I would get the #'s off it and get one.

 

[G_Hipster]

Its a Holley 2B on a 2008 Volvo 3.0 GLP-J. I think its a 2300.

I think a full carb rebuild will happen once I give up on this seasons temps.

.

Get the kit and get it sorted instead of messing with bits and pieces. If it is indeed a flooding issue, fuel washing the rings in the meantime is never a good thing

 

[185StingLX]

A full rebuild is still likely but I tried a new needle/seat just to satisfy my curiousity. I set the floats as described and re-adjusted the idle screws with a vac gauge instead of a tiny-tach that I installed. Best day on the lake so far!! The engine required no throttle on any start (including dead-cold). I had stated that I never had any trouble in no-wake zones and that was evidence, in my mind, that the needle and seat were OK most of the time. But the needle/seat must have been leaky all the time because the engine is happier doing everything from idle to WOT.

I was reading about 18in on the vac gauge at about 850 RPM and the engine seems happiest the the idle screws out about 5/8 of a turn. 5/8 seems like quite a distance from the 1.5 turns out starting point. Does that indicate any other possible issues?