I trickle charged my car to a full battery over 48 hrs. I drove it ~20 miles (no radio/lights). I then let it sit for 4 days. I went to start it and it is trying to turn but never turns over. If i jump the car it turns over almost immediately. The battery is 6 months old. I disconnected the negative lead and used a 12v tester. There are no leaks to be shown. I first thought it was the glow plugs (3 years old) but when the car is being jumped it turns over immediately. I am very confused as to what to troubleshoot.