Fuel cut off valve page L 73 +2 manual

Has any one got one of these fitted?

I am about to fit one as I am now convinced the car in losing petrol through the carbs when the car is parked.

i notice it on page 73 of the workshop manual but have never seen one on a car.

What was lotus’s reason for fitting one?

( its is always open when the ignition is on)

Zetec,

Can’t answer your question but I think you should investigate the fuel loss. What are the symptoms and how much are you losing?

I’ve had a similar problem in the dim and distant past although not with Webers. The cause was a faulty float valve causing the float chamber to overfill and fuel to leak constantly but only when the engine was running as the fuel tank was lower than the carbs. When the valve got worse, the car overfuelled and ran very rich. It’s probably worth a quick check to see if the fuel levels are ok in the float chambers.

With a +2, the fuel tank is high. I haven’t measured the levels but I suspect that fuel would run through the system through gravity if there was no valve to stop it. Mind you I would also expect the fuel pump to stop the flow although I can’t remember exactly how its valves work.

good luck
Mike

carb float levels are the correct and valve seats are in good condition.

It says in the manual to fit one and I have been meaning to do it for 5 years so I will do it and see how I get on.

I would have thought the pump would have stopped it.

I have noticed if from empty I add 1 gallon of fuel drive the car around the block till warm say 1 liter gets used I then park the car 2 -3 weeks later there will not be enough petrol to start the car initially I put this down to evaporation or a small leak in the tank.

No leak (pressure tested tank when I had it out). no leaks.

To test evaporation i left a 5 liter petrol container in the garage at the same time with no lid as a reference to measure evaporation.

not much evaporated.

Do you get a strong petrol smell in the garage? Litres going missing seems rather a lot.

Mind you could be using a gallon very quickly if you are driving ‘round the block’ from cold. Urban driving from cold may well give you much less than 20 m.p.g.

You could measure it more accurately by brimming the tank (from a spare can) when you park it up and then checking how much is needed to top it up after a week or two.

If you take the intake box off, can you see whether the carbs are wet with fuel when the car has been standing?

If you have a traditional rubberised fuel pipe to the carbs, you could clamp it when you park up to isolate the carbs and tell you whether the cut off valve would help.

Mike

I’ll guess it is fuel tank evaporation. There are many threads here on the subject, both carbs and fuel tanks. My '69 +2 can make one to two gallons disappear in about three to four weeks if not driven.
I’m no scientist but I think the open can idea doesn’t replicate the liquid surface area and airflow the +2 tanks provide (they’re good for Optimum evapoative processes it seems.)
Does anyone know of another classic car that has such a fuel evaporation problem as the +2 ?