When the car is parked for about 1 day then the carburetor seems to have emptied. The fuel pump needs to be primed by filling fuel directly from an external source. I don't know if the problem is some sort of syphon effect returning fuel to the tank, a very slow leak from the carburetor or some other problem. The rubber pipes look to be in good condition. No apparent drips from base of carburetor. Any ideas. Thanks
Technical Fuel loss from carburetor when car is parked for 24 hours.
- Thread starter Mypanda
- Start date
Currently reading:
Technical Fuel loss from carburetor when car is parked for 24 hours.
This question is actually from my 126 but I imagine the question is just as relevant here too. The design of the fuel system is probably the same as on the layer 500s with the latest engines and Fiat600s
Last edited by a moderator:
Sounds like you have an air leak,
And it is syphoning back
And it is syphoning back
smart51
Established member
I had this on my car when I first got it. If the car had been running and had stopped, it would fire right back up. The following day, it needed to be cranked for ages before it would fire. Someone suggested replacing the jubilee clips on the fuel hoses with proper fuel hose clips. It worked for me.
The theory is that Jubilee clips are not quite round so the hose doesn't seal properly. They don't let fuel out, but they let air in. After sitting over night, enough air had leaked in to the pipe to break the syphon or whatever stops the fuel draining back into the tank.
The theory is that Jubilee clips are not quite round so the hose doesn't seal properly. They don't let fuel out, but they let air in. After sitting over night, enough air had leaked in to the pipe to break the syphon or whatever stops the fuel draining back into the tank.
- Joined
- Sep 27, 2020
- Messages
- 317
- Points
- 144
I know it’s not reassuring, but I can confirm that my car with all new lines and new fuel pump fires up within a handful of seconds even if sat for a week or more. So you shouldn’t have to crank it for an extended period after just 24hrs!
When you mention manually filling the carb bowl with fuel, is that just to save 20s of cranking or without that will it simply never start? If the latter, I might take a closer look at the pump.
When you mention manually filling the carb bowl with fuel, is that just to save 20s of cranking or without that will it simply never start? If the latter, I might take a closer look at the pump.
I must admit I don't keep on cranking time and time again.I know it’s not reassuring, but I can confirm that my car with all new lines and new fuel pump fires up within a handful of seconds even if sat for a week or more. So you shouldn’t have to crank it for an extended period after just 24hrs!
When you mention manually filling the carb bowl with fuel, is that just to save 20s of cranking or without that will it simply never start? If the latter, I might take a closer look at the pump.
Having said that, I don't understand why there isn't sufficient petrol in the carburetor itself from the last time it was full, just a day ago.
Is there a breather pipe on the petrol tank?
If the pressure inside the tank drops below the atmospheric pressure if it is a closed volume due to lowering temperature, then the lower pressure could suck the fuel from the pipes and pump. Just a thought.
smart51
Established member
An air leak where a rubber hose meets a metal pipe. For example where the wrong type of hose clip has been used. I've found that taking the hose off and reseating it has helped.
A fuel hose that is drawing air..
So the line fills with air, and the Fuel pump then struggles to "pump air"
You priming it with fuel is your clue there
I anledning don't know what you mean by the hose draws air. Could you explain that please. ThanksA fuel hose that is drawing air..
So the line fills with air, and the Fuel pump then struggles to "pump air"
You priming it with fuel is your clue there
There all puntos
Member
If you remove the tamper cover on a 2 litre jug of milk, and just put the cap back on, it will spill all your fridge and table if it falls down.
If you only remove it half way and pour some milk from it and put the anti-tamperback down, and the cap back on, you can kick it about your kitchen (and striking sharp implements excluded) it won't leak.
This is because, the air can't get inside, causing the milk (or in your case fuel) getting out. No air, means a vacuum is formed.
In your case (maybe) causing a syphoning of the float bowl.
If you only remove it half way and pour some milk from it and put the anti-tamperback down, and the cap back on, you can kick it about your kitchen (and striking sharp implements excluded) it won't leak.
This is because, the air can't get inside, causing the milk (or in your case fuel) getting out. No air, means a vacuum is formed.
In your case (maybe
) causing a syphoning of the float bowl.smart51
Established member
To draw means to pull, or in this case, to suck. He means a small amount of air is leaking into the fuel hose.
Correct, and the air will sit high in the hose (an air pocket)
This will act as a "spring".. The fuel pump only managing to suck tiny amounts of fuel,
as this air pocket damp the pumps effectiveness.
