Carb flooding

[djgreen]

Gents

Still trying to get this '69 roadster started !

I've got the fuel supply working but when I pull the choke on full, fuel flows rapidly from the front carb air inlet (under pressure from the fuel pump)

I think it is the jet assembly but before I replace it does anyone have any suggestions ?.

Cheers

Dave

[Ian F]

Sounds as if the needle valve in the float chamber is not doing its job? This valve should close (by a float) when the chamber is full, and the pump should then stop ticking.

Check that the float is floating(!), Check the setting arm, and finally consider replacing valve seat and needle.

Ian F

[djgreen]

Thanks Ian

That was my first thought, so I cleaned and checked the float chamber (dry so not certain the float is floating -although it is not full of fluid- or that it is adjusted properly but the needle does block the intake)

The fuel doesn't flow out when the choke is in and the pump is on ?? Which made me suspect the jet assembly. Maybe it is still letting fuel through but much less noticeably ?

I'll recheck the float adjustment

Cheers

Dave

[Ian F]

I think the choke just lowers the jet and opens the throttle butterfly a tad? I think I would focus on the float chamber components and adjustment if you have flooding problems. Are you using a standard fuel pump and not a high pressure aftermarket unit? You may need a pressure regulator if you have an aftermarket pump.
The valve and seat of SU carb float chambers can be quite troublesome - they may look OK but still leak a bit.. I would recommend the newer Grose Jet type - one upgraded part which seems to work and is hardly any more expensive than the standard part!

Ian F

[Vic Butler]

Switch the ignition on but don't start the engine. The fuel pump will be heard ticking then the ticking should slow down and then stop. If it doesn't stop have a look around the carburettor float chambers to check for flooding.

[djgreen]

Good news 👍👍

Managed to get the engine started and up to running temperature - although running rough I am chuffed as I bought it as a non runner with loads of bits missing from the engine or removed and in boxes.

Which leads me on to the embarrassing admission of not noticing one of the carbs had the wrong float chamber lid. It is the rear one and has a straight through fuel inlet as apposed to the breather inlet from the float chamber. I connected both together which meant the front chamber was being flooded from the rear via the breather - if that makes sense !

Anyway I blocked them off and no more flooding 😊😊😊

Thanks guys for pointing me in the right direction and stopping me from wasting money on a jet assembly.

Not sure where the wrong chamber lid is from but I'm thinking of keeping them both blocked until I can get a second hand replacement - how important is the breather connection I wonder ?

Cheers

Dave

[Ian F]

That's good!!

I think I would need at least one photo to make any sensible appraisal!!

Ian F

[djgreen]

👍
I’ll try to post a few pictures tomorrow

[djgreen]

As promised photos

However with these blocked it would not start this morning . Could be due to no choke, but when I reconnected them it started 🤨. I assume the flooding was helping 🤪
Anyway I’ve sourced the correct lid now 👍

Cheers
Dave

[Ian F]

Dave, thanks for the photos. What you are calling the breathers I have always thought of as emergency overflows for when the float chamber valve malfunctions. But I guess they also allow air pressure to remain constant if there are variations in the levels of fuel in the chamber. They should each have a rigid steel pipe attached which extends down well below the carbs. and is open at the end.
I will attempt to post photos of both carbs on my BGT which are as original (although with K&N filters).

Ian F