Fuel draining out of float

[pottsthomas]

I've done this discussion before but it's come back around. My stock carb was draining out the float. I read about the check valve solution and how that was just addressing the symptom without solving the problem which was most likely internal in the carb i.e. Gunk preventing the valve from seating correctly. I bit the bullet got a new 1800 intake manifold and a 32/36 Webber and problem solved. But..... It returned and with an obviously junked up gas tank it replaced it. Blew out fuel lines and figured I was good to go. Added in a check valve just to be sure. Nope. Now put on an electric fuel pump so I can at least get the gas back in without cranking the engine for 5 minutes. But now I'm wondering where is the gas going. With the check valves it's not going back to the tank. It must be draining in to the intake and from there to the cylinders and from there into the sump. Does that sound feasible? If so what would the likely culprit be in the carb?

The sad news is I've picked up a rattle on the lower end and when I changed the oil it seemed suspiciously thin like maybe I fried a bearing with thin oil.

[TimpanogosSlim]

You mean the bowl. The float is the thing that floats in the bowl, which is responsible for closing the needle valve when the bowl is full.

Carburetors aren't rocket science. Well, they sort of are rocket science in that they are pretty fantastic hydraulic engineering. But I think you'd be well served by taking the top plate off and having a look around.

It could be gunked up. I've seen pictures of fancy viton tipped needle valves turned to goo by ethanol fuel (so solid brass needle valves are preferred). It could be that your float is adjusted too low so the bowl never has very much in it to begin with.

Without air getting sucked through the throat(s) of the carburetor the gasoline isn't going to get sucked through with it. I doubt the bowl is just draining into the engine.

[pottsthomas]

Yes sorry for not being clear. Of course I'm referring to the fuel in the float bowl when I'm saying float. I have an mg with SU's and a common condition is the needle valve getting gunked and not shutting which then allows fuel to continue coming into the float bowl and eventually pouring out over the exhaust header. It doesn't seem like gunk on the needle valve is my issue. If it were incorrectly adjusted float level then I would think my problem would be more consistent. I only have start up issues after two days of sitting. My fuel filter is just off the supply to the carb and I can see its full. If the fuel only gets sucked out of the float bowl my the negative pressure of the piston downstroke I don't see where the fuel in the float bowl is going?

[Dawgme85]

I haven't responded to your problem until now because of the check valve you installed, which should prevent fuel from leaking back to the tank. However, your symptom is the same as what I had; i.e. hard starting after sitting for a few days. I had this same problem for quite a while with my 1800/32ADFA combination; if the car was warm or only sat overnight, it would start right up, but if it sat for longer than a day or two it would take 15-20 seconds or more of constant cranking and pumping the throttle before it would finally start, after which it would be fine until the next time it sat.
What I finally discovered was that the inlet and vent barbs on the carburetor top plate both had become loose, to the point that I could rotate and wiggle them with my fingers, including one time when the inlet barb actually disengaged from the carb and pumped gas into the engine compartment! With the barbs so loose, air can leak into the fuel line and allow the gas to (slowly) leak back to the tank (I could actually see bubbles forming in the clear filter after shutting the engine off as evidence of this) I tried switching carb top plates with one which had "tight" barbs from a different carb, but the problem returned after a short time (couple of weeks or so), so I finally had the carb top plate modified to accept threaded hose barbs, which appears to have now solved the problem (it's been a couple of months, now, with much easier starting after sitting for as much as 2 weeks). I thought about it, but never installed a check valve, believing this to be merely a bandaid on a more serious problem that should be solved properly, and think that a threaded connection is a better solution. Good luck.

LeRoy

[pottsthomas]

problem has been solved, but not sure exactly how. Put in an electric fuel pump along with the check valve and recleaned and checked over the weber 32/36. No more starting or fuel draining issues. Ha!!

My lower end rattle had nothing to do with the bearing. It was a smashed oil pan, broken oil pump pickup, and slight contact with a connecting rod. No other damage, offending parts replaced, and car is running very sweet.