Fuel and carb problems

[Timmy Wainwright]

Hi guys, I am after some advice on my MGB 1978 roadster, if possible.

I have recently changed the fuel pump due to it failing stopping the engine starting,
I thought this would solve the problem, instead now with the increased pressure to the carbs it overflows and won't start. Probably flooding the engine.
I am presuming that the carbs need work to allow for the increased fuel pressure for the car to start? The front carb fills up with fuel, am presuming this floods the system.

Any help would be massively appreciated.

[Peter Cresswell]

Hi Timmy,
You are not alone! Firstly take a look at these previous threads on the Forum, which are about similar problems and may help to solve your issues:
http://mgbforum.mgb-register.org/viewtopic.php?f=4&t=66

and this one:
http://mgbforum.mgb-register.org/viewtopic.php?f=4&t=74

You say you have changed the fuel pump. Is the new one an MGB spec SU pump, or have you changed to something like a Facet?

[Timmy Wainwright]

Hi Pete,

I had the carbs off and had a look! Both were full of rubbish and muck so gave them a good clean, turns out its the seat and needle valve that needs replacing.

Have booked it into AJ Griffiths in Derby to be done tomorrow, so hopefully that should solve it all. The fuel pump was a like for like replacement, so that shouldn't be a problem.

Many thanks for your help.

Cheers,
Tim

[Peter Cresswell]

Hi Timmy,
I hope that fixes your problem. It should as it is the most common reason for SUs flooding. Make sure they fit the VITON tipped needle valves. Perhaps consider also having a fuel filter fitted before the carbs if you are getting muck in the fuel bowls.

Also, if your flexible pipes are the originals and these can be the source of the muck as much as the tank, for the future consider replacing them with flexibles that are compatible with modern fuels as the ethanol rots the older rubber based fuel lines. Stevson Motors in Selly Oak, Birmingham are often highly recommended for these. See http://www.stevsonmotors.co.uk/Stevson% ... epage.html for details.

[Dave Linkson]

Some aftermarket fuel pumps will overwhelm the floatvalves and cause flooding. What like for like replacement pump did you fit? an OE SU pump?
If you've had the carbs off and cleaned them out then it's very easy for you to replace the needle valves. Viton tipped needle valves are all you can get now, avoid grose valves.
A good tip is to use just a small drop of redex in the fuel to help stop varnish/gum build up caused by unleaded fuel. Super unleaded fuel is supposed to be best for cleanliness, and use an inline filter, and change or clean it every now and again.