A: There's no way to compel a member to vote. Let's say you had a special rule of order requiring those members present not to abstain. Your councilman could wait until everyone else had voted, then go with the majority (in effect, abstain); or he could even vote first, then change his vote later if it was the minority position (thus, again, effectually abstaining). And there really are legitimate reasons to abstain, including just plain not having a strong enough opinion.

However, your councilman has a civic duty to study the issues being voted on, and to vote using his best judgement. If he continually fails in this duty, you might consider steps to have him recalled.

Technically, he doesn't stop the democratic process; he just doesn't participate in it, and leaves the work and responsibility to the remaining members.