CamH Posted July 13, 2007 Share Posted July 13, 2007 My front SU carb is having a strange problem, it's dumping a LOT of fuel up through the fitting on the float circled in the attached picture. I took the four screws off the top of the float and tore the cover off, a little brass fitting above the float had simply fallen out and was loose in the bowl, so I screwed it back in to where it was supposed to be. This seemed to help a tiny bit, but a lot of fuel is still being dumped. If anyone could give any suggestions on how to fix this, I would appreciate it. Sorry if the post was difficult to understand, I am not very familiar with carbs. thanks! Cam Quote Link to comment Share on other sites More sharing options...
hughdogz Posted July 13, 2007 Share Posted July 13, 2007 I think what you're describing is that the needle valve fell out. What I think may be happening is that the fuel is pumping into the bowl but the float won't close the needle valve. Then you could get fuel spraying out of the top of the float chamber through the barbed fitting like you're describing... Check the needle valve and see if it will still seal when closed. If not, get a new one from Ztherepy in Salem. If it still works, you may have to adjust the float. If it is not contacting the needle perpendicular, it may not close all the way. To adjust the float, bend the mounting tab so there is ~3/8 inch space between the top of the float and the cover (...I'm not 100% on the 3/8") ensuring they remain as parallel as possible. This is also how you roughly adjust the mixture (the fine mixture adjust ment is the knob below the jet nozzle). Also, it might be a good idea to attach a hose to the barbed fitting, then into a container to catch any gas spillage while you're testing... Did this all the sudden start happening? Maybe the return line is somehow plugged or kinked? -HTH Quote Link to comment Share on other sites More sharing options...
CamH Posted July 13, 2007 Author Share Posted July 13, 2007 Yes, this just randomly started happening when I was stopped at a light the other day, the line was dumping in to the air cleaner and flooding both carbs so the car was running extremely rich, so I took it home and started to take things apart. Just to make sure before I order the wrong part from ZTherapy, is the part I want called float valve? I can't find anything called a needle valve and I don't want to order the wrong part. Thanks! Cam Quote Link to comment Share on other sites More sharing options...
MrFancypants Posted July 13, 2007 Share Posted July 13, 2007 Float valve. Definitely sounds like your problem. May as well order two (one for each carb). Could even get a seal/gasket kit and new jets and needles to do a total overhaul. I think you can get just the valves from AutoZone. - Greg - Quote Link to comment Share on other sites More sharing options...
Tony D Posted July 16, 2007 Share Posted July 16, 2007 Yep, Float Valve is stuck down, or not sealing. My 77 Impala would do that after a long run...would pump out of the vent in the center of the carb---would have to jump out and bang on the body to get the float to seat the valve. Bad thing was it was doing thin in 1979... So 30+ year old SU's are forgiven! LOL Weigh those floats, make sure they aren't leaking and filling with fuel, causing them to sink. My friend recently replaced two of his floats, as it had failed all around the solder joint at the center of the float. You can boil the floats (brass ones) in hot water....if you see bubbles coming out of the float, you know you got a leak! Sometimes you can solder over the hole you see (do it while it's hot, so the solder will be 'sucked in' as it cools, instead of having air blowing out as you heat the float to solder it!) but you have to be careful not to make the float too heavy, or the bouyancy is affected, and you end up in the same situation you were in with the leak! Good Luck! Quote Link to comment Share on other sites More sharing options...
fhptom Posted July 24, 2007 Share Posted July 24, 2007 Definitely not what you want to happen. When I first got my 260 it did the same thing and the raw fuel was dumping right onto my exhaust header. Luckily no fire. Shut it down on the side of the road and adjusted floats to get me home and then redid the whole carb. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.