air suspension problems

Hello everyone, I am new to this site. I have a '97 expedition 4x4 with air suspension. Filled up at a gas station week ago and when I restarted the engine , the compressor did not come on and "check susp" light was on. I shut the engine of several times and same problem. Disconnected batt. to see if something needed to be reset, same problem. I manually gave the compressor 12 volts and it came on and filled air bags. I did this several times through the week and now when I manually inflate the bags the 2 back ones aren't inflating anymore. Does anybody out there know whats going on? Thanks.:evillol: :banghead: