VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1912-1928 fuel starvation

Hello
When my 23 roadster is on the drive, it idles beautifully- but on the road, when attempting to cruise long in top, or on any incline, the car starts to miss and backfire.
I think it's fuel starvation- I let it tick over on the side of the road, and (presumably) a head of fuel builds up, and we re away again.
The vacuum system seems ok- the float is good, and it seems to work until called upon to work a bit harder. I did notice the gasket at the top of the unit is not in good condition.
Anyone with experience of overcoming this problem?
Thanks

Steve

When it pops and stumbles, let off the accelerator for a couple of seconds and then hit it again. Does it still stumble? If so it is the carburetor or ignition. If it runs well for a short time then begins to stumble it can be the vacuum tank.

Howdy Steve.......It sounds like you may have found an air leak....loose clamp, old hose, or something like that...

Thanks for the reply.
it pops and stumbles, but keeps going for a fair while- a quarter of a mile or so, but with no power there. If I throttle off for a short while and then accelerate, still no difference, in fact if I do that the car is more liable to cut out.
The car starts again when stationary pretty easily, and if I let it idle for a couple of minutes I can drive off again with full power until I get in top and cruise along for a little while or hit a rise, when the popping starts and power falls away.

Thanks for the reply.
Can that be in the tank fuel line, or the vacuum pipe from the manifold, or the gaskets on the vacuum tank? Or is one of these more likely?

Howdy Steve....I think I would check the line between the fuel tank and the vacuum pump, then the vacuum line to the vacuum pump. Hopefully you'll find a suction (low pressure) leak, if not you may have some disassembly to do. Just a thought..do you have a filter on the fuel line?

With the additional information, I agree that is seems to be a leak or partial blockage.

There are several places to check:

Wrap tape tightly around the vacuum fittings and check again. The tape will help seal any leaks. Also check the gasket on the top for leaks. Tape might be wrapped around the top to canister edge for a temporary seal. Or use oil around the edge with the engine running to see if any gets sucked into the gap.

Drain the vacuum tank to measure the amount of fuel in it.

Blow back on the line from the v-tank to gas tank checking for restrictions.

Add about a pint of gas to the inlet fitting (use small funnel and hose) of the V-tank. That should give about 4 miles worth of gas. Run the car and check performance.

Those should tell you if it is the vacuum tank or plug somewhere.

You may have hit the nail on the head there.
I dissembled all the joints, and when I took the fuel inlet off the top of the (carter) carb, I found it had a heap of black debris in there.
I have also found a bit of a blockage in the line there, so have cleaned it all out, replaced the line, and put in a modern fuel filter.
I can't try he car until the weekend because work is in the way, but will keep you posted. Hopefully things should be improved. The car sat for many years in a museum an wasn't used, which is never good for old ladies...
Thanks to you guys for helping out.
Steve

Just to let you know gentlemen, I took the car out today and motored to Glastonbury, and then climbed the Mendip Hills to admire the vista.
It went without missing a beat- fuel problem resolved.
Thanks for your kind assistance.