Carburettor starting problem

[taznuv]

Hello all, wonder if any of you have come accross this problem before.

My old Alfasud which is in pretty good order, and normally an excellent starter, won't start without a lot of cranking if I leave it for more than about a week. I'm reasonably convinced it's lack of fuel, as the amount of cranking required is always the same to get it to start, and when it does start it runs perfectly. Battery, compression, ignition etc are all good BTW. It runs a Weber progessive twin choke, like a DGAV I think but smaller. I've come accross this when leaving a car in hot weather for a longer period, but surely it can't be evaporating in a cool garage after a week. I'm thinking it must be leaking out of the float chamber but can't see any sign externally.

any ideas?

thanks

[rev-erend]

Go buy some 'Easy Start' .. spray it into the carb before starting ..

If it starts easily - when you would normally expect it to turn over loads of times before starting .. then it's an issue with either fuel drain off or evaporation from the float chamber and the engine driven pump has to replenish this fuel before the car will start easily again.

[350zwelgje]

Seems to me that the carburettor can vent too quickly and too much (and the easy start elements of petrol) have evaporated.
Isn't there a way to prime the reservoirs to overcome your problem?
Have this issue myself with a car that I have planned to bring back to live since many years, and it won't start but once it has done, it will for a couple of months or so at the first click. Haven't got my head around priming it myself as oilpressure is used as a safety to the electric fuel pump and that needs by passing without triggering the starter... (for information: not Alfa, Rover SD1 with SUs).
Sorry if it is not making sense as haven't played with carburettors in a very long time.

Rob

[GoingUnderCover]

Is the fuel pump engine driven? It sounds like the float chamber is evaporating empty over time, and then needs to refill by cranking the engine over before it'll start. A separate electric fuel pump would prevent this by priming the chambers ever time you turn the ignition on.

[taznuv]

Thanks for the thoughts all. Yes it is a mechanical pump, I had thought about adding an electric but it seemed a little drastic if there might be a simpler fix.

Good comment about the volatile parts evaporating off/carb venting too easily/draining, will look into this. Maybe a carb rebuid is needed.

Rob, I had thought if I did add an electric pump it would have to go through the oil pressure sensor for safety. I imagine in your case you could add a push switch somehow in parallel with oil pressure switch, then a prod of this would switch the pump on (and the oil light out) with the ignition on. Having said that I'm unfamiliar with how they wire in electric pumps so this could be nonsense! Of course with injection they have a sensor to detect a crash situation which makes the system safer still.

[Jerkins]

My x-flow powered kit car now has an electric pump, wired through an inertia switch I bought via ebay (I think it was intended for a Rover). It looks like this one (but the supplier I used included the connector).

http://cgi.ebay.co.uk/Rover-200-25-Tomcat-Fuel-cut...

It's really easy to wire in - it only has 2 wires that are normally connected when in normal mode, so you just wire it into the live side of the electric pump. Any severe impact or roll-over will break the circuit and disconnect the power to the pump - in fact, on my car it disconnects all the engine electrics, including the Megajolt ignition system. A quick push down on the rubber cap will reset it if it disconnects unexpectedly.

[taznuv]

Jerkins, looks like a good solution, thanks.