Starting problem on 2001 Ford E-150

She is running fine ,battery about 2 yrs old . She doesn't get used often and when she does,it is short milage. About 3 weeks ago when I went to start her, she turned over easy but didn't fire. When hubby came home he bought some starting fluid and she has been fine until today.However since then she has only been used 3 times max? and 20 miles total? Could it be a weak battery or weak fuel pump?

Asked by for the 2001 Ford E-150
The answer is inconclusive. Basically, at the car, you have to see what is missing. If the engine cranks well enough, the battery is not an issue. If starting fluid helped, could be a fuel pressure issue. Only by testing at the point of failure can a true cause be found.
I too have a simliar problem, E-150, 2001 conversion van. Mine is used infrequently for short distances and has been turning over fine, but refusing to start periodically. Sometimes i can wait a couple of minutes and then she will start just fine. The engine cranks, battery has plently of juice, just won't start.
Again - could be as simple as a fuel pump relay issue. Could be a intermittent bleed down of fuel pressure. Could be a loss of cam or crank signal. Only testing while the problem is occuring will reveal the answer.