Help!! Not sure if this is an alternator, battery, or fuel pump issue?? Went to start this morning, and had to put my foot on the accelerator to keep it running. Battery was a little dead, had to jump it, then started it. It died immediately. Can't keep it running for the life of me. Getting battery tested in a bit, how do you test the alternator to see if it's bad? Any other Ideas?? Please Help?

2000 Dakota sport, 4.7 automatic 4x4 156k miles

 

So it turned out to be a bad battery, which was only 2 years old as of April. Starts right up now!!!