Why engine keeps flooding?

[Super Mario]

Hi this is on behalf of my Dad. He is working on a 1969 Morris Minor with a 1000cc engine. Petrol keeps flowing straight into the bores. He has dried out bores and put new spark plugs in - engine runs for about 5 seconds - bores completely filled with petrol again and the plugs are soaked. He dries the plugs and bores but it just keeps happening over and over again. Took float chamber lid off carb. Filled float chamber with petrol, cranked engine for less than a minute and carb chamber drained of petrol straight into the bores. Any idea what the problem is? Thank you.

[bmcecosse]

Is there a needle in the carb ? Should be attached to the piston that rises and falls. Also check - is the float chamber vertical - and is the choke control (it's not really a 'choke'!) completely off ?

[Super Mario]

Yes there is a needle on the carb. The float chamber is vertical. Choke is completely off and seems to be working normally. He has fitted new needle and choke chamber.

[bmcecosse]

What size carb ? Are the needle and jet same size ? ie Axx needle in a 90 thou jet ?? And - erm - what's a 'choke chamber' ?? Not understanding that!

[Super Mario]

The choke chamber jet. Needle and jet are matching set. Don't know the size. Have tried another carburettor - same problem.

[bmcecosse]

'Choke chamber jet' - no - not getting that.......... However - if you tried another carb, and still have the same problem - it's obviously NOT the carb! Does the car have the standard SU fuel pump fitted ? If a non-standard fuel pump - then probably the pressure is too high and it's simply flooding through the float chamber needle valve.

[Super Mario]

Forget choke chamber. I meant needle and jet. It's a brand new standard fuel pump and even with the pump disconnected and manually filling the fuel chamber the problem is still the same. The engine was reconditioned recently. Could there be a problem with the engine or could a new carburretor solve the problem?

[bmcecosse]

Well no! You've tried another carb already! I really don't get it - it runs for 5 seconds - sounds ok when doing so - then it 'floods' even if no petrol is added to the float chamber ???

[Super Mario]

Firing order is correct. New contacts, condenser plugs rotar arm distributor cap plug leads and two sets of new plugs have been fitted. It has a good spark. Tried two coils. At one point the engine was running very high revs only.

[bmcecosse]

Has the engine run 'normally' since the 'reconditioning' ? Are the valve gaps all set correctly? Assuming the cam timing is ok - can only suggest advancing the ignition timing until the engine kicks against the starter - then retard slightly - it should start there!

[kennatt]

you say that you filled the carb manually and after cranking for less than a minute the carb was empty and engine now flooded am I understanding thats what you are saying,Very Very strange if correct.

[mike.perry]

Can you post a few photos of the carb?
I think that you need to start afresh and go through each step at a time and report on the result.
1st test. When you turn the ignition on does the fuel pump tick rapidly then just the occassional tick?

[bmcecosse]

This seems to happen 'even with the pump disconnected' Mike! .............. I'm waiting to hear the answers to the Qs I posted earlier........

[Super Mario]

This is a recap and update on everything my Dad has tried so far.

He got the engine from an unfinished project. The original owner obviously had problems so he has inherited these problems.

Engine is re-conditioned and has never really run. New fuel pump fitted and clicks until carb float chamber is full, then clicks on occasions.

New points, plugs, condenser, dist cap, rotor arm and leads have been fitted. He has tried two new coils as well. Valve clearances have been set to 12 thousand.

He has set the engine up by checking top dead centre. No 1 piston TDC Both valves closed. Checked rotor arm is on lead No. 1 and has set firing order, valve timing and ignition timing are okay and engine is getting a good spark.

Engine has started and run on full throttle with choke when cold. When he tries to run engine slowly, engine stops and then will fire again for a short time then floods. He has tried another carb and the same thing happens again.

When he removes spark plugs and turns the engine over, petrol continuously comes out of boars more significantly on cylinder 1 and 2.

He took the lid off fuel float chamber and filled chamber with petrol, cranked engine and watched float chamber fuel disappear in less than a minute.

He is now powering fuel pump for very short periods of time to allow a little fuel into float chamber. This has the effect of the engine running for 20 to 30 seconds at a time. After a few attempts like this cylinders 1 and 2 flood again.

This problem really has him stumped and he is grasping at straws. He is thinking maybe a hole in manifold between inlet and exhaust could be drawing in the extra fuel?

Any help or ideas would be very gratefully appreciated.

[bmcecosse]

If it runs for 20-30 seconds - there's nothing very much wrong with it! A hole in the manifold -would draw in air - not petrol! Is the petrol pump definitely the right one for a Minor ??? Does seem like the carb float bowl is over flowing - has a new valve been fitted - and the level set ??

[Super Mario]

It is an SU fuel pump bought from Morris Dealer. Have tried two carburettors and problem is same and have set needles and jets according to workshop manual in them.

[bmcecosse]

What needle is in either or both of the carbs ?

[Super Mario]

He looked at the markings today and thinks it's either a AN or NA???

[bmcecosse]

AN is standard for the HS2 carb.

[mike.perry]

If you lift the carb piston with your finger does it drop onto the bridge with an audible clunk?
AN is a standard needle for 1098 or 1275 twin carb engine.You beat me to the answer Roy.
I think we are missing the "bleeding obvious" which a couple of photos may reveal.