Good evening all! I hope you have been having a most excellent weekend but now I must quiz those who have had a bit more experience with carburettors!

Basically the fuel in the carb is boiling from the heat of the engine. If you put your ear to it you can hear it bubbling and its forcing fuel out into the inlet through the accelerator pump jet and maybe other places too. This means I stop the car after a journey and it slowly pours fuel into the manifold which makes it bloody hard to restart!!

Now I can think of 2 things that might help:

Disconnect the heated manifold pipes from the coolant system ( not sure this will help as the heat will surely still ride up the manifold with conduction anyway - temperature might be greater without the coolant system flow?)

Build a heat shield round the carb from aluminium or something ( the exhaust and inlet are both on the same side on this engine (Y10 Turbo) so heat from exhaust and turbo might be getting to the carb by radiation.

Anyone else have any more suggestions? Anything you can buy to cool a carb?

Cheers,
Si

Firsty, huge respect for solving a very difficult problem with the worn butterfly mentioned in your main MM thread. I know the engine is a little "hot", if you'll pardent he expression, but I'm suprised the issue is so prevalent that it is causing fuel to boil. Makes you wonder how it is meant to work in the standard Y10.

Heat shields will have an effect and is a good place to start.

You can buy fuel coolers. Modern diesels commonly use them due to high fuel pressure generating heat.

Having more fuel in the tank may help as the fuel itself will be cooler before it gets to the carb.

X1/9s suffer from this, never come across it in a Panda before. On the X1/9 there is a heat shield which fits under the carb - presume the carb 'footprints' are different between the cars however. They also have a cooling fan directed at the carb which is triggered by a temp sensor. Many people question the fan's effectiveness, and disconnect them because the fan can stay on after the ignition is off, draining the battery. Hope you get it sorted, David

On other cars I have heard of people doubling or tripling up the carb gasket between the carb and the manifold or making up their own thicker one to help reduce the amount of heat conduction.

excuse for an impreza style massive air scoop on the bonnet?:devil:

A plastic thermal block between the carb and inlet manifold is a common solution used by manufacturers, but I think you would probably need something else too, maybe some thermal wrap around the exhaust manifold if there's room.

Cool, thanks for the suggestions guys. I didn't know that this problem was so well known! I will certainly try the cooling fan if I can find one. Or perhaps make up a cooling system of my own. I have already put a plastic gasket in between but the studs are not long enough for a thicker or additional gasket; maybe I can fit longer studs...if I can find some

I did think about some sort of air scoop on the bonnet too but went away from the idea because its a bit obvious (detracts from the sleeper look) and that it only works when moving so it will still cook when stuck in traffic.

I could fit a fuel cooler but I expect it wont stop the fuel in the float chamber from boiling over after the engine has been turned off.

I will also look into some thermal wrap for the exhaust manifold in addition to a heat shield; anything to carry the heat further away from the inlet has got to be a good thing!

Certainly need to have some more profound brain things inside my head!

Thanks again for all your suggestions.

Cheers,
Si

Heat shield built awaiting a road test to get some heat into it

Nice work Si, hope it works for you .

Thats a nice heatshield!

Could you take an air feed from the side of heater intake shroud (putting a peek over it to stop water getting in), then fitting a computer case fan in the ducting...

If you suck air from the intake onto the carb, then you shouldnt get any oil smell in the cabin with the heater on.

Thanks guys,

I'm not 100% convinced an air cooled solution is that effective as I have been reliably informed that cooling systems like that were fitted to Renault 5 Turbos as well as x1/9s and that most people gave up with them anyway. Air just doesnt have the heat capacity in my opinion so I am coming up with a water cooled system should the heat shield not be enough.

Damn weather is stopping me from putting carb back on though!! Bloody sun all day long all week and it picks friday evening to start chucking it down!!:bang:

Si

ARG!! Well I am not convinced that this problem is due to carburettor over heating anymore. I ran the engine till it was really hot and left engine to stand. I kept feeling the outside temperature of the carb and it kept pretty cool now. But still the fuel started to pour into the inlet through the pump jet. And a slight bubbling noise from inside somewhere. maybe the heat is just rising up through the idle circuit from the inlet manifold but if thats the case what the hell do I do to overcome that!!

I think I have just got to cool the whole engine down more in general. So going to look for a better radiator next. The current one is on its last legs anyway as it sprung a leak when I first started her up lol - I did the evil radweld solution at the time. ( don't judge me )

Oh and I should have done my dynamics calculations as the heat shield has a resonant frequency around the 1200 RPM mark lol Just needs a bracket I think, or something rubber to push up against it.

More to come! Probably going to be continued on the marbella's own thread from now on though...I'm moving away from general discussion :devil:

Si

Si

I think anything rubber pushing on it will melt

Are you sure the fuel is boiling? It could be excessive fuel pressure forcing it past the float chamber valve.

Couldnt be a blocked vent could it?

Does that system have a return to the tank?

I don't think its fuel pressure but worth a check. The float chamber would be over filled if that was the case but its always at normal levels when I check. And it happens when the engine is off so no fuel pressure should be supplied apart from built up pressure.

I did think it was vapour return system related simply because I have blanked that off! There is no vapour return to my tank because of the original panda engine it had didnt need it. I've tried opening this up before though and it didn't help but perhaps there is something in the system I am not fully understanding.