As an auto tech for the last 30 years, I've been through the carburetor open loop era, closed loop era and now just when you thought they were ALL gone, one shows up at the shop. This was a carry-in QJet off of a 1970 GS 350 with the complaint of flooding immediately after start-up. Normally I won't touch a carb unless there is a car attached to it, but I've known the owner for a long time as he delivers parts from a decent salvage yard a few towns away, and he is a Buick guy. The engine would start and run fine, but after a few seconds, fuel would pour out the top. It had a "reman" sticker on the side of the float bowl. What could go wrong here? I installed a kit and float from Ruggles and set the float level and adjustments as best I could without a car. So I give the carb back to the owner, and a couple of days later, it shows back up with the same problem. Hmmm, so I decided to find enough "stuff" to adapt the -8 fuel line on my 494 to the older, smaller fuel inlet of the 70 Qjet. I bolted it on, and sure enough, it flooded just like he said. I removed the carb and air horn, and the bowl was over full. I checked the float setting (correct), and did a crude pressure check of the needle and seat for seating -OK. Maybe a piece of crude from somewhere was caught in the needle and seat, so I blew it all out again with compressed air, assembled and installed carb and ran the engine - no change. WTF, I have worked on 100's of Qjets over the years, but maybe the knowledge was being lost from lack of use... I may not be the sharpest tool in the shed, but I never give up! Off and apart again, and looking REAL close at how the float, needle and seat work, I then spotted the problem. Anyone care to take a stab at it? It so simple but in 30 years I had never seen it. Probably had something to do with the sticker on the side of the float bowl, but it could happen to any Qjet.
Nope - it did it before and after I "rebuilt" it. New parts were float, needle and seat, accel pump, spring, choke pull-off, etc. The typical kit didn't fix the problem.
Remanufactured carburetors are the worst. They frequently have mismatched parts because they are built from piles of parts, instead of rebuilding an original carburetor. We just had a member with a flooding problem because the air horn gasket he was using was wrong, and it was hanging up the float.
No mismatched parts and no well plugs or anything else leaking. Classic carb flooding over out of the bowl after running long enough to fill and then overfill the bowl.
If it has all the correct parts and the parts are all good. I would guess that the needle 'wire' was installed incorrectly on the float. If not I would check hinge pin, bowl stuffer, something that causing the float and or needle and seat to not operate correctly.
I would say the float is not holding in place by the needle seat. Wrong float pin or the plastic cover were wrong, bent or something? Fuel pump pressure?
We have a couple of winners! Remember, though, that the carb was on 2 different engines, and I had replaced the float with a new one, with no change in symptom. What I found was the float hinge pin (the c-shaped pin that slides through the float lever) was bent. The top, curved part was closed up a bit, and there was no way for the air horn to keep the pin secured in the float bowl lands. When the fuel pump was filling the bowl, the float was rising. With pressure on the float and fuel pressure on the needle, the float and needle both rose because the float hinge pin was not being secured correctly by the air horn, resulting in no way to shut the fuel off. When I had the carb apart the first time today and was crudely checking the sealing capabilities of the needle and seat by blowing into the fuel inlet, I was holding down the hinge pin with my finger... I have never run into this before, and is something else to check when rebuilding one of these old carbs. I don't know if any of you carb builders give the hinge pin a little tweak apart or not, but it would seems that if it was a little wider, it would be pressed together during the installation of the air horn, eliminating the chance of it not holding the float and needle correctly. HTHs somebody someday!
We were close. :TU: I had one hinge pin recently that was bent up too far. So have you determined what is the best height above the plastic cover that the top edge of the pin should be? That may be good for future reference.
Well that is something else to check that I have never thought of, I'll be sure to keep an eye on that from here on. :grin:
Was your bent up hinge pin causing a problem? I would think that it would get pushed down to the ideal preload location when the air horn is installed? I don't know if there is a "checking height" of the hinge pin or not. May an experienced carb builder can chime in. I have a bunch of NOS small carb parts from when I worked at Rchester Products in the early 80's, so I just bent the pin to match an NOS one.
Was the float bowl insert in place? Normally, that part keeps the float hinge pin bottomed in the groove so it can never ride up higher and mess up the fulcrum point. I've seen some carbs without it...and it causes fuel to slosh around a lot, too.
Yes, the float bowl insert was in place. If I remember correctly, the older Qjets ( such as this one) had a more open designed insert in the area of the hinge pin. The later ones were more closed, which assisted in keeping the hinge pin seated. This stuff is being purged from my memory banks at an all too fast pace!
