Sleeps if battery installed

I picked up a Macbook4,1 2008 2.4GHz that had suffered a liquid spill (well actually salad dressing in a backpack on the left side :-) The display had some oozage (is that even a word) on the left edge so I replaced it with a new display. The other issue was that it would not boot all the way since it always thought it was in sleep mode (the sleep LED stayed lit throughout the boot). I could get it to temporarily wake up by hitting the enter key but it immediately wanted to go back to sleep. There were signs of charring on the battery connectors both on the battery and on the connector itself (I guess salad dressing conducts).

So I have ordered a new battery/sleep connector for it. In the mean time I had a spare battery/sleep connector of unknown status (from the same model 2.4GHz) that I decided to pop in and it seemed to work!!! or so I thought. I had booted it up with no battery and everything seemed just great. Then I shut it down and reinstalled the battery and fired it up and.... same symptom as before... sleep LED stays on, machine partially boots and then goes to sleep. Hmmmm.... removed the battery and it boots fine.

So the question now is... is this second power/sleep cable also defective (came out of a Mac I picked up for parts.... no obvious signs of damage... it looks new) or is it possible that there is an issue with the logic board? Any ideas or thoughts before I get the known good part to swap in?

Many Thanks