Fuel. Priming

[John Clarke]

Hi All.
Has this been done , or even feasible ? We all know how quickly our Carb Float Chambers dry up / evaporate. Wondered if it is both safe or possible to adapt a Spare Gas Tank Lid fitted with a pressure regulator ( Set at 3 PSI ) and a Tire Valve fitted to the inlet side. This would then easily connect with one of those electrical tire pumps available. So, pumping direct through the gas tank. , Pet Cock through to the Carbs.
Just a thought, am I mad? Didn't know if the Petcock would be up to it ?
Just thinking
Jay

[Emil Wojcik]

I don't know if pressurizing the tank is a good idea on a system that wasn't designed to be pressurized.

[Wes Bender]

It would certainly prevent the float bowls from drying out, but would also provide a constant source of fuel to evaporate. The question would then become, how long would it take to evaporate the whole tank rather than just the float bowls. Did you think that all the way through Jay? Or did I miss something.....

[John Clarke]

Hi Wes
Not sure if You missed it, or I didn't explain properly !
This would only be used momentary for pre start carb priming. As Emil mentions above, the system isn't designed to be pressurised, but we are only talking of 3 PSI.
Cheers Jay

[David Aronson]

An auxiliary fuel pump for priming works. I have a similiar but less problematic starting in the 912. If I park it for a few weeks the delortos dry up just like the Zeniths. The fuel pump is more efficient, and only after a few moments the spitting and sputtering begins. I plan to put the same system in the 912 just to save the starter and battery.

[Mike Wilson]

I wonder if anyone has considered a submersible electric fuel pump as used in modern cars.

Mike

[John Brooks]

submersible will have 40-80 psi for injectors I would not try that on a 356

I have 2 methods to prime mine. I use a big hypodermic and put 25cc of fuel in the carburetor vent tubes, if the car has been sitting for a few months. I then allow it to wet the inside of everything for a hour or so before starting, make sure the accelerator pumps are working then fire it up. #2 is the good old outboard motor squeeze bulb between the tank and the fuel pump. Easy on the 912 with more accessible fuel lines. I have also mounted a 6V vibrator pump with a momentary switch on a couple other peoples cars, both under the passengers foot rest and under the car by the torsion bar tubes. They work fine for easy and quick priming. also a good back up for a mechanical pump failure.

[John Clarke]

John and David This is a different method to all the conventional methods of various pumps and primers and has been covered extensively on the registry. With respect, don't want to cover all that again. Just wondered if pressurising the system externally would work.
Jay

[David Jones]

My procedure if car has been sitting for a week or two. Disconnect maintainer from pigtail attached to regulator, check oil level, apply some throttle, spin engine over until oil pressure warning light extinguishes. Pump throttle with up to 10 even strokes. Attempt a start, if no start then pump throttle again and try again to start.
If it does not fire remove air cleaner and check for fuel squirts from accelerator pump jets. Rarely does it fail on any of my cars. The existing fuel system works very well though having an electric fuel pump is nice insurance for that one in ten thousand chance of failure of the mechanical pump.

[Mike Wilson]

Good point, John B. Way too much psi!

Mike

[Wes Bender]

Hi Wes
Not sure if You missed it, or I didn't explain properly !
This would only be used momentary for pre start carb priming. As Emil mentions above, the system isn't designed to be pressurised, but we are only talking of 3 PSI.
Cheers Jay

Thanks. Somehow I couldn't see maintaining any pressure on the tank. That would involve some control over the tank vent too. I am of the school that uses an electric pump to prime the carbs if they sit for a week or so. Most of the time it is only a day or two and no priming is necessary other than the four or five pumps with the throttle.

[John Clarke]

Wes You are correct. I hadn't considered or even thought of the Tank Vent Pipe. Many thanks. The idea is rubbish
Jay

[Martin Benade]

The idea could work ok but starts to get more complicated if you add a solenoid vent valve to the tank. That is a standard part on every modern car, so it’s not outlandish.
I’m not sure about it but if the standard cap is unvented you would only need to connect a switchable pump/vent to the original tank vent, it’s not the worst idea.

[gregg hake]

Dont our tanks have vents, so there isnt a vacuum formed as the fuel pump pulls fuel out of the tank, thus keeping anyone from pressurizing the tanks?

[Mike Wilson]

Correct, Gregg.

Mike