Michelle,

When you turn your key to START, you are powering the solenoid to pull in and connect battery voltage to the starter to spin it. The way you have described the problem, my first thought would surely be a bad battery. This would be true only if the cables were in great shape, clean and connected well.

There is a oxide or crust that forms on the positive post and cable where it clamps onto the post. This is a tough material and must be 'cut' off with a knife. After this is done, the little post cleaner do-dad can shine the lead and finish the job.

Unless you know the history of your 'good battery', it would be my very first suspect. If you have a remote starter switch you can attach it to the little terminal on the solenoid and the big lug that has the BATT cable on it. This will take any other wiring out of the loop and prove the battery.

If you don't have the remote starter switch you can use a old screwdriver to jump from the little 'S' terminal on the solenoid to the big BATT lug. Make sure your rig is in neutral.

I sure would think bad battery first. Good luck!

Stuart