I have a 99 3.0 that when I got wouldn't start. So I got some starting fluid in there and it started and was starting atleast 10 more times after that over a two week period. Now its only starting when I put starting fluid in it. I can hear the pump when I turn the key and once its running it will run but as soon as I turn it off It wont start again.

 

1 Plugged fuel filter
2 Water in fuel tank (Condensation from sitting)
3 Fuel pump / regulator failing
4 Fuel pump relay failing

Get a fuel pressure guage and check the pressure at the fuel rail.

Is there a CEL ? What are the codes ?

 

there are three things you need to get an engine to start...
1. compression
2. fuel
3. spark

Now all you need to do is process of elimination. Good Luck!