T24 Carb problem

[David.H]

The jet underneath the carb is fixed It was clear when I reassembled it I think, but I will have another go! - There is a small fibre seal down there that I couldn't dislodge....maybe that is the culprit. I have a new one in my "kit" although it seemed a touch large,,,I will get the old 'un out somehow & try again!
Thanks again!
D

[David.H]

The saga continues!
Got the main  jet fibre washer out and was unable to blow though to the venturi. Did a bit of digging at the base of the venturi and eventually was able to get a clear passage from the main jet to the venturi.
That will fix it thinks I.
Reassemble everything, starts fine on the choke.......Attempt to do without the choke & the engine immediately stops. By closing the intake completely with a hand palm fuel was sucked in - & the engine ran without choke very briefly.
A quick old style test of liquid sprayed onto the inlet gaskets (manifold & carb) did not change the engine note, so no  sign of air leaks there to weaken the mixture.
The car runs remarkably well fully choked! ticks over well, pulls ok, no exhaust black smoke. I drove it around the block without problem, so what is left to examine/change?
It seems to me that the base of the problem is that the engine is starved of fuel unless choked.
So what else affects this? About the only thing left in my thoughts is -
Float level? There is a 1.5 (marked) needle valve - the correct one according to the book! and it appears to open & shut perfectly. It has one washer (aluminium?) from the overhaul kit. but is the (non punctured !) float at the right height? How significant is this?
Fuel flow. There is a clean in line filter...I will remove this to see if that alters anything, but I am not hopeful as fuel flows freely through it and when running fully choked, the engine revs remarkably freely!
I don' t want to drive around with the choke pulled out....so what next?

[John Mason]

David. I am no specialist on carbs but if it run reasonably well when the choke is out. That leads me to think that the closed choke is correcting the air to petrol ratio and it runs reasonably well. Opening the choke upsets this and the engine stops (to much air). The level of petrol in the float chamber is critical to get the correct air/petrol ratio. As air is drawn down the Ventura this alters the air pressure making it lower than normal air pressure thus more petrol to more air keeping the balance of petrol/air the same whatever the throttle setting.
So your thinking of float level could be the answer. Is it to low.

John Mason

[David.H]

Thank you John

So I need to set the shut off needle valve to operate sooner, ie to have less fuel in the float chamber.
Naively if I put another washer under the valve seat, this should lower the needle & thus the level by the same amount (about a millimetre)...is that significant I wonder?
I know the "1.5" of the needle valve refers to the size of the intake (diameter?)
D

[AustinWood]

If the problem is lack of fuel then surely the fuel level should be raised.
The correct level must be specified somewhere.

[David.H]

Hmmm! more food for thought.
It is, of course a non standard carburettor & all I have found is the jet etc sizes, apart from Tim Reynold's excellent article....which I will now re- read!
D

[Bryan]

Hi David, it does sound like you’re not getting enough fuel. If you can set up a temporary supply and line to it and see what happens.

[John Mason]

David, Higher the level of petrol in the float chamber. Take out a washer from the delivery valve if you can. To lift it higher. Also always remember what you have done in an effort to improve things so that if there is no improvement you should return things to how they were.

John Mason

[AustinWood]

Have a look at this:
http://zenithcarb.co.uk/zen24/?___store=zenith
I think it specifies fuel level etc

[David.H]

Thank you!
Now to measure 15mm fuel height!
No problem ...this carb is on & off like the proverbial!
Just need a steady hand>
D