starting when hot

[davidp57]

hello
My 950 is not good to start when hot, the engine has been completely rebuilt and uses no oil ,it starts first touch when cold and runs fine.
It is using too much petrol , a new needle and jet have been fitted but the plugs are getting very sooty.
I have adjusted the mixture down as far as I dare without affecting the running but no joy , I have ordered a rebuild kit for the carb and will fit it as soon as it comes ?
David

[ssnjimb]

Is the needle in the carburettor correct.

One tool i recommend if you call it a tool is a Colortune kit

Jamie

[bmcecosse]

Don't waste money on a colourtune !! The SU comes with it's own mixture setting device - the 'lift pin' !! But I suspect the problem is a leaking float valve...when you turn on the Ign - the fuel pump should click ywo or three times then stop.. If it keeps on clicking - the float valve is leaking...

[minor65]

You mentioned that you screwed the jet / mixture screw as far down as you dare. Screwing the mixture down makes the mixture rich. Screwing it up makes it weak. I would screw it up providing engine noise keeps staying 'nice'. And engine can rev up freely / nicely. Then if your still happy with performance, replace your sooty plugs with new ones champions / ngk's. Then drive car for a while and check colour of plugs. Ideally should be a (plain) rich tea biscuit colour.

[mike.perry]

You should need some choke when stating from cold but none when hot

[davidp57]

You should need some choke when stating from cold but none when hot

It is a new M needle and jet and sorry I screwed it up not down ,I served my time on the BMC range but this has me puzzled ,I have ordered a new rebuild kit and will fit that when it arrives.
After cutting the mixture down it would not pull so I gave it more until it would run right.
It needs choke but not for long ,I will replace all when the kit arrives and try again.
Cheers David

[bmcecosse]

If you've already fitted jet and needle....I wouldn't be bothering with a kit!

[darren1camper]

I had exactly the same problem thought it was fuel evaporation after trying everything changed the rotar arm and hey presto turned out the bakerlite in the rotar arm was faulty.
Regards
Darren

[davidp57]

I have fit a new rotor arm from distributor doctor but it made no difference.
Dave

[bmcecosse]

And have you checked the float valve ?

[davidp57]

And have you checked the float valve ?

No but after the first couple of clicks from the pump it is silent , however I will be fitting the float valve when the kit arrives.
David

[bmcecosse]

Hmmm - so it's not flooding (that's a good enough check ) - it would be interesting next time it's 'hot' to pour a little petrol in the carb inlet and crank it. If it starts right away - then petrol delivery is the problem....if it's still reluctant to start - it's an ignition problem.

[andypocock]

And if it's neither it's a bit tight after it's rebuild

Andy

[Heronwood]

I had problems with my float valve. it was made out of copper and became porous it slowly filled up with rule and then sank!

This meant the fuel pump clicked all the time, fuel flooded out of the primer button and and spilled all over a very hot exhaust!

beware…..

Mike

[Trickydicky]

I had problems with my float valve. it was made out of copper and became porous it slowly filled up with rule and then sank!

This meant the fuel pump clicked all the time, fuel flooded out of the primer button and and spilled all over a very hot exhaust!

beware…..

Mike

So did mine, I drilled 2, 1mm holes in it ( one in the leaking hole) to drain it and then soldered them back up, it's been fine since.

[MarkyB]

made out of copper and became porous

What were you using for fuel?

[davidp57]

I am using unleaded with addative.
I have fit the overhaul kit from Bull motive and was surprised that there was no needle in the kit which they tell me is the case.
I havn't had time to give it a good run yet to check the plugs for sooting but I will post the result as soon as I give it a run.
Dave

[bmcecosse]

No need for 'addative' (sic) - just run on the unleaded - it's fine.

[davidp57]

I have now given the car a decent run but the plugs although not sooting up are still too dark I am going to fit a new needle and try again.
Dave