97 elantra fuel pump problem?

I have a 97Elantra wagon which has trouble starting about once a week. If I tap the underneath of the gastank while turning the key,it will usually fire up right away.
However, one day this week it wouldn't start at all. Strangly, the next morning it started right away once I tapped the gastank.
Has anyone else had this problem? Could it be a fuel pump problem? if so why doesn't it happen while the car is running?
Thanks for all responses. Dave (and confused).
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If it's cranking and won't start and tapping the underside of the tank makes it start, then it's almost certainly the fuel pump. It's very rare for Hyundai fuel pumps to fail in this manner, but I've seen it much more frequently on GM cars.
The reason it won't start is that the brushes are worn and not touching the pump. Tapping the tank probably vibrates it enough for the brushes to touch and the pump to start running. Once the pump is runnng, it's likely to stay running because the motion keeps the brushes at least partially in contact.
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