Won't boot. Tried troubleshooting ram, worked and dead again

Ok... So I am at my wits end here. I have a a1278 macbook late 2008. I have a relatively new battery, new power cable, and 8 gb of ram with 2 sticks. I also have replaced the keyboard before.. Which was a pretty intensive task.

Here is my issue. My mac stopped booting up and I assumed the ram, motherboard, or hard drive. I put it aside for a while as I didn't want to dump more money into a old machine. Well, I still am not at a point I want to jump on a new computer so I figured I'd try fixing again. Tonight I took both sticks of ram out, held down power for 10seconds, let up a second, then held down again. To my surprise it started beeping no ram! I was incredibly excited. Put a stick back in. Put the back back on and did the same power cycle. It booted!

I thought I would see by trial and error if I had a bad ram slot, a bad stick of ram, or if both would work. Tried adding both. Dead. Tried one. Dead. Tried the other. Dead. Even without ram in I can't get it to beep again.

So, any suggestions? I'm confused as to why it booted and now won't. Also, it took quite a while to run any tasks when on the short time it was working. I could view files on the hard drive so I am assuming that the hard drive is not my issue.

Thanks for reading and any suggestions you might have.