Another scary moment in a P2

[RobHomewood]

Last weekend in the lovely hot weather I had just topped a long hill in the P2 (47 16 engine) when I smelled petrol really strongly. I stopped in the nearest layby - luckily only about 1/4 mile - switched off and opened the bonnet. Petrol was pouring out of the carb and over the hot exhaust. It continued to pour out even though the engine and pump were off. (It has an electric fuel pump). I really thought it was going to blow and ordered my wife out! About this time I made a mental note to get a fire extinguisher on board before next trip! Nearly an hour later when the breakdown mechanic arrived he thought the cause was a slightly loose screw on the float cover and once tightened it seemed fine. But I am wondering whether this was a gasket leak because it seemed on first sight to be pumping out of the top (air cleaner opening) and then a pilot jet air bleed (I think-I find the diagram of the 30FF1A carb difficult to interpret as I haven't dismantled it yet). I stuffed some chewing gum on it to staunch the flow anyway - messy but effective. Could it have been that the float was stuck after the long uphill pull? Would the fuel have come out of the jet orifice or whatever in that case? Could that be caused by excess pressure from the electric pump? I will replace the gasket anyway but would appreciate some advice from more experienced P2 owners.

[47p2]

Check the needle valve is not sticking as this is a common problem with the Solex carb.

The fuel pump should stop pumping when the ignition is switched off, check that the pump is wired correctly

[luli]

Solex 30FFIA can leak petrol even if all gaskets are in perfect condition and the cover is tight. This is because the float chamber has an overflow outlet that allows petrol to flow out if its level is too high.
This can happen for several reasons:
1. Incorrect fuel pump. Modern electrical fuel pumps produce high pressure. The P2 carburetor is designed to operate with pressure of 1.5 – 2 psi. The fuel pressure can be measured with an appropriate gauge (normally a vacuum/fuel-pressure gauge). If the pressure is found to be too high a fuel pressure regulator should be used or the fuel pump replaced to the correct type (AUA25).
2. Leaking or incorrect needle valve. The correct one is No. 1.5. If higher than that – it should be replaced.
3. Incorrect fiber disk between the needle valve and the cover. If it is too thin the fuel level may be too high. Add another one.
4. Incorrect/damaged float. The float wight is written on it (normally it is 26 grams). Remove it, clean it and weigh, replace if necessary. You can also switch to a lighter float: I have met P2 Solex carburetors with as low as 23 grams floats.

[lakesrally]

I'm suffering similar problems with my P3 at the moment. I changed the needle valve this evening and there seems to have been an instantaneous improvement. Will use the car for a couple of days and see if it really is fixed.

[RobHomewood]

Thanks for all your prompt replies and advice, you have confirmed my suspicions I think that it was not a gasket leak. I shall investigate the options including re-installing the Purolator fuel pressure regulator which I have found in the parts box- on checking the pump is rated at 2.5 to 4 PSI which could be a contributory factor. Its a good way to get familiar with the carburettor workings if nothing else!
By the way 47p2 the fuel pump does switch off with the ignition with an additional switch on the dash but I think in this case there must have been excess pressure in the fuel line/carb, aided perhaps by being parked facing slightly downhill
Rob

[chris dancey]

Sorry I'm a little late. Luli is correct on all points, I have experience of a friends 1948 75 who contacted me with petrol flowing out through the solex carb. He had fitted a facet fuel pump with a 4+ pressure rating, this was the problem, I advised him to fit a flow regulator set at 1.5 .....did the trick, no problems since.

[lakesrally]

After changing the needle valve I used my P3 for a week as my daily driver and it never missed a beat. Running better than it has since the National at Blackpool two years ago.