Fuel Vapor Affecting My Health

[NovaF4]

Hi Lauren

Many years ago I bought that little red anodised device from Demon Tweeks that I was referring to in my reply to David, but never fitted it. I remember you emailing me with help about where to fit it. I'll have to dig out the email, unless you can remind me. Does it go in line with the breather pipe? I think you said locate it high up but my breather pipe exits the side and goes downwards into the wheelarch.

I've bought a good large fan and tried it, with mixed results.

I had those carb plastic pushrods off the other week whilst experimenting with the springing force at the pedal end. Granted - taking them off would stop the fuel jetting into the carbs when I'm testing the throttle pedal and would greatly reduce the problem I'm experiencing. But, I need them attached in order to give the throttle pedal a 'full travel' stopping point, as this is crucial during what has become an extremely tedious experimenting process which is draining me of enthusiasm.

[islandman]

which is draining me of enthusiasm.

Don't let it drain you, but you could try draining the tank, then with no fuel inside there is nothing to be squirted into the carbs....Just a thought as I remembered draining my tank when sorting my sender unit out.

[NovaF4]

David - I can’t believe I didn’t think of that. So obvious. Maybe I’ve lost more brain cells than I thought.

[islandman]

Giles, you are in good company with me, clearly I wasn't the only one who couldn't think straight. Brett made what in hindsight is an even more obvious suggestion, and doesn't involve draining the tank....."could he not just disconnect the fuel line to the carb or disconnect the accelerator pump instead of draining the tank"

Sometimes the obvious answers seem so obvious ONLY after someone points them out

[NovaF4]

I think I'll stick to your suggestion. I have 4 fuel pipes - 2 for each carb, as you well know. If I take them all off then fuel would vapour out of them as well as the breather pipe. Maybe it could syphon out too.

I've no idea where the accelerator pump is. Never worked on that before. Do you know?

Another idea would be to remove the fuel pipe from the in-line filter and clamp it off. That would save draining any fuel but the breather pipe would still vent vapour.

The first thing I should do is fit the valve. That will hopefully stop vapour exiting the breather pipe. How is your valve fitted David?

Then if I still need to do a lot of throttle pumping I'll either try my idea with the clamp or drain the tank.

Thanks for all the ideas.

[Spacenut]

Many years ago I bought that little red anodised device from Demon Tweeks that I was referring to in my reply to David, but never fitted it. Does it go in line with the breather pipe? I think you said locate it high up but my breather pipe exits the side and goes downwards into the wheelarch.

I had those carb plastic pushrods off the other week whilst experimenting with the springing force at the pedal end. Granted - taking them off would stop the fuel jetting into the carbs when I'm testing the throttle pedal and would greatly reduce the problem I'm experiencing. But, I need them attached in order to give the throttle pedal a 'full travel' stopping point, as this is crucial during what has become an extremely tedious experimenting process which is draining me of enthusiasm.

Hi Giles - it sounds like you have got some sort of breather valve, although there are many types to choose from. My original device (also anodised red) was a roll-over valve which simply stopped the fuel draining out of the breather if the car ended up on its roof. With the car right side up it did not do anything to stop the fumes from building up in the garage.

The valve should be fitted in the breather hose and vent to atmosphere. It doesn't matter where the valve is fitted (high up or low down), it does not affect its function. The valve that you want should have some resistance to pressure in both directions (try blowing through it) - that way the valve will prevent fumes from escaping (unless there is pressure build up do to heat or filling the tank with fuel), while at the same time allowing air back in to replace fuel as it is used by the engine.

Your carbs have an accelerator pump which is operated by a pushrod attached to the throttle butterfly bar in between the two chokes. The pump is formed from a diaphragm in a square housing on the side of the carb with a lever connected to the pushrod. Not an easy thing to disconnect without removing the carbs from the engine I'm afraid.

Easiest thing to do is to disconnect and plug the fuel line from the tank. You could siphon the fuel out of the carburettor float chambers by whipping to tops off, but the easiest way to drain the float chamber would be to operate the throttle and let the accelerator pumps empty the float bowls.

However, this puts quite a lot of neat fuel down the cylinder bores, which can dilute the oil on the cylinder walls. Best bet is to take the spark plugs out and crank the engine over to expel the fuel from the cylinders.

Once the float bowls are empty of fuel you can operate the throttle with fully representative spring resistance. Hopefully it will not be long before you hit the ideal combination of settings. Keep at it, it will all be worthwhile in the end.

I have just spent a similarly frustrating weekend adjusting the self-park position on my Lucas 15W wiper motor. Because I am using tailgate contacts that only make with the canopy closed it has been a slow, iterative process which has cycled the canopy about 20 times. I know I previously made up a set of jumper wires to link the motor to the wiring harness with the canopy open, but I just couldn't be bothered this time... Still, everything seems to be working now.

Lauren

[islandman]

The first thing I should do is fit the valve. That will hopefully stop vapour exiting the breather pipe. How is your valve fitted David?

Then if I still need to do a lot of throttle pumping I'll either try my idea with the clamp or drain the tank.

Thanks for all the ideas.

I have a shut off valve mounted to a side wall just below the tank (about 6 inches of fuel pipe from the tank to the shut off valve). Another alternative is simply disconnecting the fuel pipe (its only one pipe) as it enters the mechanical fuel pump, simply plug that and the inlet to the mechanical fuel pump to stop any draining back. You could also once this is done just run the engine till its stops and your carb float bowls have emptied themselves.

[NovaF4]

Good idea. How would you plug the fuel pump?

[islandman]

Good idea. How would you plug the fuel pump?

get a small section of fuel pipe (5 cm), put one end on the fuel pump inlet, put a bolt (or dowel or similar item) inside the other end and clamp a jubilee clip around it. Job done, no back flow of fuel or vapours

[NovaF4]