hard starting

So I've been having this problem for a few weeks. Ever since I bought my XJ. It was my boss's. It sat literally for six months without being even so much as turned over. It took forever for the battery to charge up enough to jump, and it doesn't like to start. Today I was at MacDonald's and when I put the key to start the car just clicked once and then nothing. Wouldn't start at all, no lights, no radio, no nothing. So I had the boys from the dealership run me up a jump-box and it still was hard starting, but eventually kicked over. About four hours later I had the jump-box with me thinking I wouldn't be able to get home without it, and the Jeep started. Took a while, but it did start. I haven't checked it out since I got home.

Here's my question: I'm sure it's either the alternator or the battery. But how do I know? I don't want to buy a new battery if I don't nee to. I've already changed the plugs and wires, cheaned off the batt terminals, and it's still hard to start. Usually, once it's started, it's not too hard to start after that for a few hours or so. And the colder it is, the harder and longer it takes to start.

It's the battery right? Old and decrepit?

I'd think the battery - just because it sat for so long.

However, year/engine? While it's doubtful, there are some electronic issues that will want looking into, after you've ruled out the battery (but I'd go with the battery first...)

5-90

Ditto what 5-90 said. I agree it's probably the battery, but you can take it to most any auto parts chain (Kragen, Autozone, etc...) and they can test the battery, alternator, and starter for you. Good Luck!

I cleaned my engine compartment today. When I started the Jeep up to move it out of the driveway, it wouldn't start. Just kept making a clicking sound. I remember having a car do that once, but I can't remember what I did to fix it. The radio worked, the lights worked, everything worked, but no start at all. Just click click click click click. I took out the battery and went to NTB. They tested it and it got a 590 out of 610. Whatever the hell that means. The girl that tested it said it was okay, but a tech came over and opened the battery up and said it was probably bad. So I bought a new battery, put it in and... It's hard to start. Just keeps making a wirring sound til I give it enough of the gas pedal to really start up. Isn't that clicking sound the car trying to get juice to the starter? Like the starter isn't holding charge or something?

Starter basics. Starter is actually three parts (maybe 4). The solenoid (large round electro magnet mounted on the side of the starter motor) that has two functions, it throws the little gear in the starter into the big gear on the flex plate/flywheel, at the same time it closes two big contacts (in the base of the solenoid) for the juice to flow to the starter motor (the part that turns). As mentioned, the motor is the part that turns, it turns the Bendix, this is the part that allows the little gear to slide on a shaft into the big gear. The motor/Bendix shaft is cut (slots at an angle) so when the motor turns it helps throw the little gear into the big gear and helps hold it there while the motor is turning.
Another component (actually number 4) is a clutch, that allows the little gear to slip, when the motor starts, actually a one way (hopefully) clutch. If the clutch is slipping, you'll get a click, whir but the engine won't turn over.
Click, Click Click is often, not enough juice to run the whole thing. Battery or the cable end at the battery pole gets dirty or oily and doesn't allow enough juice through to get the job done. Same with the ground wire, same with the ground wire at the battery or on the motor block. Same with the plus battery cable at the battery or at the starter motor itself. Cable ends are dirty or the nut/connection is loose. Loose mounting bolts for the starter can also cause this problem, either the starter is hanging at an angle or the bolts aren't tight enough to make a good ground contact.
Whirring, is often the motor turning, but for some reason the little gear isn't going into the big gear on the flex plate/flywheel. The shaft is gummed up with grease, mud and trash or the solenoid isn't working well. The motor mounting bolts are loose, so the starter is hanging at an angle (grab it and shack it). Or the clutch is bad. Solenoid *mechanical* problems are rare, it's usually something else (electrical connection).
Starter takes a lot of juice. A volt measurement during start often shows around 9 volts, the battery at rest often shows around 13-13.5 volts. If any connections are iffy, the solenoid may not work properly, the motor may turn slowly and the Bendix becomes iffy.
Sometimes the brushes inside the starter make a poor contact, also causing an electrical flow bottleneck.

Clear as Mud?

Well the red cable at my battery is actualyl showing through. The red shielding doesn't go all the way into the batery terminal. Should I just putthe old battery back in and wait for it to start, then take it to NTB and find out where the problem is?

I'd clean the cable ends that clamp onto the battery and the battery terminals with a solvent then lightly sand them until shinny (both the battery terminals and the cable clamps inside).
Then check the other end of the cables at the starter and the oil dipstick holder. While I'm down by the starter, I'd give it a good shake and see if it's about to fall off.
Or call AAA.