2000 6.5td won't start but fires

[fiano]

Got home from work this after noon and went to the truck before I left I put he battery on charge turn the key waited then it started right up I though to my self must be the brand new x2 batteries ran for about 45-60 seconds it shut off in it own ok so I went back turn the key and bam started right up again this time it ran for 20secomds tried again started ran for about 10-15 seconds this time I thought ill time it 6.5 seconds
Then one more time turn the key nothing just turns over??,

[trbankii]

Ok, so it sounds like you’re fighting two fronts. The charging was definitely an issue since you were able to start it repeatedly on the charger. Now I’d start working to determine if you’ve got air in the system. As 5150 said, "you can also insert clear fuel line on the return line to see if you have air bubbles in the return fuel."