By checking do you mean you looked at them and said "they look good" or did you pull each ground connection and wire brush it? It makes a difference, they can look good externally but still have corrosion you can't see.
Also check the cables themselves. If they are unknown age/history, then replace them. 4 gauge or 2 gauge, dealer's choice on a 12v system unless you're running a winch, then go heavier. Battery and ground cables can look good on the outside and on the ends but be nothing more than a tube of corrosion on the inside.
Get a fuel pressure gauge and get some readings. Just because it's running doesn't mean the fuel pressure is good. There is a pressure test and a volume test. Usually if they pass the pressure test they're going to move enough volume. The volume test is a little more involved. Seen more than one Jeep that would start ok but run like garbage especially under load and it was a weak fuel pump.