Jump starting my 4.6

[galbre]

All,
The other day I ran my battery down and tried to jump start it using one of those portable jump starters. I fully charged the jump starter but my suv just would not turn over. I wound up using another car to jump start it.

Are these jump starters just not powerful enough to turn over my V8? I had previously used it to successfully jump start a v6 Chevy Blazer.
I'd like to be able to count on it in case of emergency but now I'm not so sure.
Gregg

 

[snickstx]

Some aren't, check the rating on the case. Also, depending on how old the jump box is it might be getting ready to die itself.

 

[Blee1099]

Depends on how many cranking amps the jump box is.. I have 2 jump boxes, one is a Diehard 750 peak amps but realstically its only like 180 amps cranking and the other one I normally carry is a 2000 peak amp with about 350 amp cranking rate. More than likely the jump box either doesn't have enough power to turn the high compression motor or you need to leave the box on it for a few minutes before cranking.