96 cont. air ride problem

The air bags are not going up on the left side of the car, right is working fine, I can hear the pump going, it goes for a bit the finally shuts off after a few mins and left side does nothing the whole time, any ideas what is causing it?

Could be the leveling sensor since the pump shuts off. Does the pump run like crazy or more than it used to?

Ya it runs a while, about 4-5 mins. Sounds reasonable, it was a repossetion (we're a car lot) and we're pretty sure it was drove a while after the left bags wouldn't come up so we figured the bags might be damaged also.