MGB Register Forum

Hi Vic,
Haven’t touched the internals of the choke devices. I have changed the connecting spindle levers location though. Initially these were resting in the large upper square hole in each choke quadrant, however I moved them into the lower smaller square hole as this gives a more efficient mechanical pull of the choke cable enabling more movement of the quadrants. Given this, it is possible that the sooting effect I am getting is the use of too much throttle for too long!

Points and condenser etc came from my NOS spares left over from my days of racing historic Cooper S. With engines reaching near 9000 rpm, only quality products would do.

Cheers, David.

Morning David.
I've had a look at the diagram of the choke operation in my official workshop manual and the connecting levers are shown engaging in the lower small hole of the carburettor choke quadrant so you're right.
Give it a good run as Charles suggested to clear the engine and try again.
. Vic

OK — just about reached the end of my tether with my car.

Thought I had it running reasonably well so would take it for a test drive today. Started the car, it popped and banged and just died refusing point blank to start again!

It is as if it is not fuelling properly, if at all ,but I ‘ve had carbs apart so many times I’m loosing the will to live.

Debating what to do next for the sake of my sanity.

Does anyone know of a reliable classic car specialist within reasonable distance of Taunton they might like to recommend?

Cheers David.

Hi David,
Assuming you have checked it isn't a fault on the ignition side,have you replaced the fuel filter? I think you said the car had stood for some months before you got to work on it . Modern fuel waxes up in the fuel filter if the car is not used for a long time. If the problem is a lack of fuel getting through to the carbs this might be your problem ( or a failing pump). If you take the feed off the front carb & place it in a container the pump should push through about a pint in 30 seconds. ( My original pump that is 38 years old manages that). Check that the hose between the two carbs hssn't collapsed internally - i had this once & found it by accident as it starved the rear carb when the car was under load during acceleration ).
Cheers, Charles

Hi Charles,
Thanks for suggestions.

I have replaced fuel filter and fuel pump, but not sure fuel comes thru at speed you quoted.

Fuel line comes out of side of tank where I believe gauge is also placed. Is there any in tank filter that could become clogged?

Have checked carb to carb fuel line and fuel seems to be present.

When replacing jets and float cut off needles, the fuel cut off seem to get easily stuck and modern fuel seems to leave dusty residue everywhere in float chamber which can’t help the situation I would have thought.

Hoping I don’t have to buy refurbished carbs just to eliminate them as an issue or not!

Cheers David.

Update — just checked pump flow rate as Charles suggested. I have a brand new electronic pump from MGB Hive and am getting only 0.6 of a pint in 30 seconds from copper pipe end in engine compartment plus flow seems very aerated. This equates to about 9 gallons an hour and am wondering if this provides enough pressure to operate carbs correctly?

Comments appreciated, David.

Hi David,
Irrispective of whether the car will actually run at all at the moment i think (i stand to be corrected by othrrs), the flow at 0.6 seems low, if not half the rate it should be as mine does 1 pint + per 30 seconds. You may have stirred up some old fuel in the tank which may have aleady clooged your in line fuel filter under the bonnet. As you have changed the fuel fump i can't comment if it has any gauzes on it that might have become clogged.
Have you still got the old pump as if off the car,easy to clean the points up on it & then check if it works & at what flow rate?
Are you sure your points haven't slipped into a permanent closed position? (80% of fuel problems turn out to be ignition problems)!
Cheers , Charles

One further thought, are you using up old petrol in the tank that the car came with or have you added a reasonable amount of fresh petrol?
Cheers, Charles

Hi Charles,
Flow checked before filter so afraid that one is crossed off the list.
Mostly new fuel.

Will check points again tomorrow.

Thanks, David.

David, daft question maybe but have you got a spark at the plug? With the ignition switched on short out the points with a screwdriver and you should get a spark. Is the carbon brush in the distributor cap OK?
This is an extremely rare fault but it happened to my BGT once a long time ago. One of the core plugs at the end of the inlet manifold had popped out. Fortunately it was still in the engine bay and the car was in the garage so I stuck it back with superglue. Very unusual I know but easy to check.
. Vic