willswitchengage Posted July 18, 2012 Share Posted July 18, 2012 Well I've put up with this for ten months now and nobody on the BX forum has any working solutions so thought I'd try the boffins here. Inheritance: Bloke who sold me the car for some reason swapped the OEM Solex for a Weber, but then discovered that whenever the car's left standing for a few days the float bowl is dry and the car takes a lot of cranking to refill the system. He postulated that somehow the fuel is simply draining back into the fuel tank through the return pipe - an internal leak somewhere. To combat this a manually operated Facet pump was installed on the fireboard to "prime" the fuel system before starting - to save on caning the starter and battery, works to an extent but if the car's been sat for a week or so it still needs a fair amount of cranking to get going. Any ideas/solutions that can actually treat the symptoms of this? Really, really hope nobody says FUEL LEAK M8. Here's a pictograph of under the hood: P1030607 by willswitchengage, on Flickr Fuel tank > facet pump > mechanical pump > canister >> carburettor and return pipe (hope you can see this) Cheers and that Link to comment Share on other sites More sharing options...
scaryoldcortina Posted July 18, 2012 Share Posted July 18, 2012 It shouldn't be possible for the fuel to drain out of the float bowl - that's like a glass of beer emptying itself (*clue is in the name "bowl") - the supply pipe and any return line are above the resevoir and the jets themselves are arranged to be close as possible to the actual fuel level in the float chamber (so fuel can be drawn into the airstream in a controlled way) leaving nowhere for the fuel to escape to unless the carb is faulty (like an internal casting fault or crack). I'd guess that this stray petrol is making its way down the venturi and into the manifold which is why you can't see a leak. Link to comment Share on other sites More sharing options...
jonny69 Posted July 19, 2012 Share Posted July 19, 2012 Typically, Webers only leak when they aren't shutting off the fuel supply and it all spills out the overflow. It's draining into the engine somehow, probably through the throttle pump. Depending on the carb, there are a number of little balls and springs down holes or diaphragms that can cause this. they are supposed to stop fuel getting through, but when they leak they can do what you've described. Either that or it's evaporating out because the carb is getting hot. Edit: or, if you haven't taken the top off the carb and actually witnessed for yourself that it's dry in there, the fuel might be running back down into the tank due to a leaky fuel pump valve. Typically, if it's this, the car will fire and run for a second, then die. Then you'll have to crank it for a bit to get it to start again. Link to comment Share on other sites More sharing options...
dollywobbler Posted July 19, 2012 Share Posted July 19, 2012 I think the main problem is that these carburettors are shite. I know another BX owner who's decided to see whether a Weber conversion makes the car behave any more sweetly as he's had all manner of fueling issues. Not fun in an automatic! Link to comment Share on other sites More sharing options...
autofive Posted July 19, 2012 Share Posted July 19, 2012 I think the main problem is that these carburettors are shite. I know another BX owner who's decided to see whether a Weber conversion makes the car behave any more sweetly as he's had all manner of fueling issues. Not fun in an automatic! dollywobbler - I get a bit miffed with your constant desire to point out how shit weber carbs are, and the people who make them. No-one forces you to use them! I find there's not much to tempt me there, so I generally keep away from them. There's much more to life than spending time with carbs you don't even seem to like! touche Link to comment Share on other sites More sharing options...
dollywobbler Posted July 19, 2012 Share Posted July 19, 2012 I think the main problem is that these carburettors are shite. I know another BX owner who's decided to see whether a Weber conversion makes the car behave any more sweetly as he's had all manner of fueling issues. Not fun in an automatic! dollywobbler - I get a bit miffed with your constant desire to point out how shit weber carbs are, and the people who make them. No-one forces you to use them! I find there's not much to tempt me there, so I generally keep away from them. There's much more to life than spending time with carbs you don't even seem to like! touche I think you need to look at this thread again carefully. The carburettor fitted is a Solex. My friend is considering a Weber as a replacement as it's apparently superior! I have nowhere slagged off Webers. Link to comment Share on other sites More sharing options...
willswitchengage Posted July 19, 2012 Author Share Posted July 19, 2012 The Weber is the problem here! Don't know why Bob took the original Solex off... weird. Oh well, something for you to look at at the the tech weekend Anyways - I kind of imagined fuel was evaporating as it usually stinks of petrol - but from where? Worn float bowl gasket? This doesn't quite explain why how the whole system was draining itself, however. The fuel filter is transparent and sometimes after a few days parked up it's still full, others it's completely drained. Bizarre. These late carb cars are hideously complicated, I also thought that the PD mechanical pump might be worn and allowing fuel to seep through it backwards and back to the tank that way. EDIt also the engine fast idles when hot (~1100, used to be higher) in case that's also symptomatic of some general carb problem Link to comment Share on other sites More sharing options...
dollywobbler Posted July 19, 2012 Share Posted July 19, 2012 Ha! Oops. I need to re-read this thread as well then! Well, my comments were about a friend replacing a Solex with Weber. Maybe there's an underlying fuel issue that a new carb isn't going to cure for him? Link to comment Share on other sites More sharing options...
dieselnutjob Posted July 19, 2012 Share Posted July 19, 2012 Edit: or, if you haven't taken the top off the carb and actually witnessed for yourself that it's dry in there, the fuel might be running back down into the tank due to a leaky fuel pump valve. Typically, if it's this, the car will fire and run for a second, then die. Then you'll have to crank it for a bit to get it to start again. my 604 does this Link to comment Share on other sites More sharing options...
jonny69 Posted July 19, 2012 Share Posted July 19, 2012 Fast idle when hot often points to an air leak in the gasket/spacer underneath. Or the throttle shaft is completely kenkered. Link to comment Share on other sites More sharing options...
willswitchengage Posted July 19, 2012 Author Share Posted July 19, 2012 Edit: or, if you haven't taken the top off the carb and actually witnessed for yourself that it's dry in there, the fuel might be running back down into the tank due to a leaky fuel pump valve. Typically, if it's this, the car will fire and run for a second, then die. Then you'll have to crank it for a bit to get it to start again. my 604 does this Oops didn't see that edit, yes this happens too if it's the first start in say... 12 hours. Anything more requires priming and lots of cranking. I'll get a new pump as they're dirt cheap on ebay and see if that helps. And Jonny, gasket/spacer underneath what? Link to comment Share on other sites More sharing options...
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