: Fuel bowl empties when engine warm

09-22-04, 01:23 PM
I'm having trouble (again) with a 68 deVille 472. I rebuilt the carburetor and, when I finally adjusted the float bowl correctly?, it ran perfectly. Sometime over the past month or so - after other repairs to various components - it got to where after about 15 minutes or so (engine warms up) the in-line filter starts to bubble as if it stops getting gas. When the engine stalls, all the remaining fuel is 'sucked' from both the filter and the carb bowl. I had switched back to the mechanical fuel pump that had been on the car a few weeks back and have since put the electrical one back on - it does the same thing with either one. It may have had this problem all along, since I don't drive it and maybe never had it running more than fifteen minutes. Maybe I didn't do such a good job on the carb.Five years ago I drove it every day with no problem.
My question is: why does it run so good when it's cold (starts immediately and fuel filter stays full), but not when it warms up? Could I have TWO bad fuel pumps and if they're bad, why do they both pump strong when cold. Is something inside the carb causing the problem? It's a pretty long lift from the fuel line to the carb - I tried putting the electric pump lower than the tank on the frame beneath the engine, but this didn't help.
I've checked the ful lines for leaks everywhere in the engine compartment - maybe a leak between there and the tank (metal line)?
Hopefully someone else has had this problem and solved it. I'm looking at changing the pump and then maybe the carb if necessary. Anyone know who sells the best rebuilts? Have had bad luck with Checker - Kraagen in the past!

10-03-04, 07:57 PM
This may sound bizarre, but I have seen one case where there was a vacuum created in the gas tank that the fuel pump couldn't overcome due to an issue with the vapor line being plugged....try removing your gas cap and letting it run....see if that helps!

10-07-04, 09:09 AM
Thanks for the reply.
I should've updated my situation though; I got the car warmed up and the problem returned. Removed the cap (thought of that also) - still wouldn't run. Tried the fuel pump out (the electric installed again) by pumping directly into a gas can - it worked. Tried blowing into the carb - no dice. Don't know what inside of it is causing the problem, but it must be the carb (I hope). I've ordered a rebuilt one as maybe mine has something that doesn't come with a kit wrong with it (since I rebuilt it already once.
I know if the float sinks or the needle valve sticks open, the carb will flood (had that problem already after the rebuild), but don't know why the needle valve appears to stay shut after warm-up?? Maybe something betweeen the fuel bowl and the rest of the carb? Hopefully not vacuum related - replacing carb won't eliminate the problem?