www.jec.org.uk

HI guys
This is all self inflicted after I messed with my carbs.
I will start at the beginning..
My engine was running fairly well, Cold starting is auto with a switch conversion, started fine.
The issue was that I would sometimes smell fuel and after checking it appeared the front SU was dumping fuel out of the overflow pipe onto ground. Not all the time but often enough.

So this is when my trouble starts. I removed the float bowl covers and found one of the needle valves was getting stuck because the float fork was allowing it to drop to far. I replaced the float fork refitted and the engine would not start. The carbs were now flooding, fuel was running out of the air intake etc.. I re adjusted the float height and it seemed to help but still wont cold start.

I now started messing with the Auto choke solenoid which does energise when power applied.

since the car was ok prior to my ruining the carb setup I am hoping that you can help me reset up the auto choke and the fast idle screw setting etc...

thanks

Hello JMD,

as the choke worke dbefore and you haven't played with it I would leave it alone.
You must set the float chambers so that no fuel floods out. The correct distance is set by putting a 7/16" diameter rod and set the float lever to that. If it still floods the needle(s) must be defective or have some dirt in them?

Alec

Thanks Alex.
I will check and reset the float levels again.
Can you explain how the auto choke works? I know that when operated it draws a rich fuel mixture from the float chamber and delivers this into the cylinders. But as it seems to be the front SU connected to the starter Carb does this mean that only the cylinders that are fed by front SU will have the fuel delivered?

How does the butterfly open when the starter carb is working? Is there a relationship between the auto choke and the fast idle? I am trying to understand how the fuel feeds through the carb body into the cylinders if the butterfly is closed.

I am asking this as I have messed about with the fast idle screw and dont know how it should be set up..

Thanks for your patience

JMD

Hello JMD,

while I have worked a lot on S.U.s, I've never played with the auto choke. It only takes fuel from the front carburettopr (It is essentially a third carburettor) but feeds air\fuel via two small diameter pipes connected to the intake manifold. The solenoid, which energises from cold via the thermal switch in the intake manifold water jacket, this allows air into the device which lifts the metering needle and allows fuel\air to be added to the intake manifold so the engine can start.
However from my S.U. workshop manual it says.
First the carburettors have to be tuned correctly.
With the engine at operating temeperature, bring the choke into operation by shorting the thermal switch wire to the engine. You may need to open the throttle a bit to overcome the high idle vacuum in the manifold. You should hear the characteristic hiss from the device at this point.
Screw the adjusting nut (This is at the top of the intake and through which the top of the needle protrudes) clockwise until the engine start to falter because the mixture is too weak.
Screw the nut anticlockwise and engine speed should increase to a maximum of about 1400 rpm, continue until the engine start to run rough and black smoke is visible from the exhaust. This should give an engine speed of about 800 to 1000 rpm. Replace the wire back on the thermal switch.

I hope this helps but ask if something is unclear or you need more advice?

Alec