car turns over but wont start, replaced fuel filter,battery,starter,alternator i give up help me

still making payments just want an idea of where to start to fix it so don't spend a lot of money for nothing

about once a month I have to jump on the back of my car and rattle it to get it to start-not fun

I had a recall fixed on the wiring harness. Picked up my car from Serra Chevrolet in Sylacauga, Alabama, drove across the road to Wal-Mart & the thing wouldn't start! Went back to Serra, told them what had happened... it had NEVER done this before & they told me it was a fuel pump problem. It wasn't anything they had done. I should have never had the recall fixed.

engine will turn over, but it will not start. the fuel filter has been changed and the spark plugs are firing