1968 Quadrajet 750cfm I rebuilt. '72 Buick 350 motor. Across maybe 150 miles of driving, twice the carb has apparently flooded real bad. I am looking for thoughts on what is happening. The first time this opccurred, I was accellerating from a dead stop. Floored the pedal to WOT, and the rear axle started to hop so I eased out of the gas. The motor went pig rich, stumbled, and died. Wouldnt start by cranking. A look under the hood showed gas all over the intake, hard to tell where it came from, but I am certain it did not come from a fitting or clamp connection, as the carb does not leak at all, normally. Second time this occurred, the car had been sitting parked for a day or two. It had run flawlessly for about 100 miles on a new rebuild. I pumped the pedal twice, like i usually do, and hit the ignition. It started but ran REALLY rough, coughing black smoke bad. Again, super rich. I opened the throttle a bit to bring RPMS up, and it stayed rough. Shut it down, looked under the hood, and again, gas on the intake. Several starts later, after holding rpms around 1500 to clear some gas out, the problem went away. Drove it a bit tonight, it is like it never happened. Ran great, no problems. Any ideas? I was thinking a sticky needle/seat, or bad float level? I just dont have the experience to know. This was my first Quadrajet rebuild. Thanks for any help! Ken G
Back in the early 70's, my 69 vette with a q jet would sometimes get crap between the needle and seat and behave just as you describe. Sometimes a rebuild will knock stuff loose that has been sitting for a while. You may also want to check for any binding between the floats and body if you are comfortable that the floats are adjusted correctly. Let us know what you find. Regards, Arland
Quadrajets can get trash under the seat as was stated but also the whole mess can be screwed up by crapy gas or varnish that got dislodged when you rebuilt it.
Your diagnosis is correct - a sticking/damaged float, or inlet needle that does not seat properly can cause this condition - the flooding can also cause a fire, so be careful ! :eek2: Sometimes a light wrap on the fuel bowl with a plastic mallet or screwdriver handle will stop the fuel from spilling into the intake, but the cause should be eliminated. Change the fuel filter element too. :TU:
Next time you open the carb, take that tiny wire needle hanger and throw it away. It can get hung-up or jamed and cause problems. You don't need it. Check the float for fuel absorbtion and look for trash in the fuel bowl. Make sure the float is not rubbing against the power valve tower or any thing else. Install the plastic insert over the front of the float bowl to control surges and high speed fuel flow. Make sure the float hinge is positioned properly (left vs right) and set the curved portion sticking straight up when you put the air horn back on.
Thanks for the help! Today I pulled the carb. Inspection found three "particles" of maybe rust or shmeg in the forward fuel bowl. Nothing was found in the needle/seat or under it. I used brakleen to flush the fuel bowl and the fuel inlet after removing the three invaders. I got another chunk of junk out of the fuel inlet during the backflush. Everything else looked fine, no interferences, breakage, bending or anything else unusual. So I put it back together and test drove. No problems yet. I am using an inline filter before the fuel pump, so I will get another one and replace it. My thoughts are that the fuel pump and hoses may have accumulated some crap while sitting in the garage awaiting my last engine rebuild. Either that or I have a bad fuel filter that is letting junk from the old gas tank through. Thanks again for the input I do appreciate the help. I will advise if anything changes for the worse. Ken G.
never use a filter before the pump. fuel under a vaccum can boil leading to vapor lock. a safety note keep a fire extinguisher on the floor in the back seat not the trunk. and for an under hood fire don't open the hood try putting it out from under the car
It is likely that the source of the rust is from the tank. It is possible for the smaller particles to get through the filter, or worse, plug the filter to the point where fuel pressure pushes the filter away from the line. This will essentially bypass the filter. One other possibility is water in the fuel. This will cause the filter to swell, and pkug up, then later, when the water disappears, the filter will appear normal. Just some food for thought. Gary is correct with respect to the float's absorbing fuel and becoming "heavy." I do not, however, recommend "tossing" the metal clip. It allows the dropping float to positively open the needle and seat assy, not requiring building fuel pressure to "dislodge" it. Sorry Gary. Good luck. Ray
"I am using an inline filter before the fuel pump, so I will get another one and replace it." You need a filter after the pump. Even theough the pump is working fine, things can come off of it.
Well the fuel inlet stuck open again, after working very nicely for awhile. Gas everywhere, wouldnt run. Murphys law, it happened 5 miles from home, with my 9 month old in the car, on the way home cause he needed his nap. I couldnt work on it properly listening to a toddler scream (you with kids know what I mean), so we walked home. He fell asleep on the way. Later we went back to fix it. So I pulled the air horn and looked inside. The inlet needle was stuck up, I felt it pop back down when I pushed on it. manipulating the float got the needle stuck up again, so I looked carefully for the hangup. It was that little hanger clip sure enough. so I yanked it, and re-adjusted my float, re-assembled the carb. Varoom started right up, no more gas overflow. So the 1st few times it happened due to junk in the carb (there was no hanger clip at that time - i installed it *after* I cleaned the carb out). This time, there was no junk in the carb, but that little clip hung it up. Maybe I have addressed all the issues with my carb this time. I can only hope.:grin: I am sure learning a lot. Thanks for all of your posts.
