"Sticky" ignition

[shaefer]

I'll see if I can describe "sticky ignition" the best I can. First off, car is a '31 Cabriolet all original engine, etc., etc., etc. Just so we're clear on what hardware we're working with here.

When I depress the starter button on the floor the engine turns over fine enough. It may be slightly weak, but it gets through the revolutions well enough. At least it does right up until it's about to ignite. If a regular revolution under starter motor power (before startup) sounds like "rauhrauhrauhrauh", then the moment before the engine starts sounds like rauhrauhrauhree - with an abrupt halt right at the very end there as if the cylinder pressure were too much to overcome. After that abrupt halt, it does not start up right away. Occasionally, if I stay on the starter, the cylinder will get a spark just after the halt and then it will come to life.

The engine runs fine, has plenty of oil and is well timed. The battery is probably near the end of its life, although like I said, it does have enough juice to turn the engine over.

And this is what has me confused. I would chalk it up to a weak battery and therefore a weak start, but it does turn over. Is there something I'm missing about the mechanical process that would answer this, or is this typical of a battery that needs replacing?

Thanks for the help! This is my first post. I've been maintaining this car with my dad since 1997, when I was only 15. Between the two of us, the car spent no less than 7 straight years as a daily driver! By far the best car I have ever owned. As the weather is just getting to be perfect, I am hoping to have her up and running just like the reliable old Belle that she is! Thanks for the help!

- Mark