working when dissasembled, not working when put together

i have a problem with one of these...

got it from frien of mine, with broken off screen. i have replaced that with one i got my hands on. machine was working correctly before the hinges snaped.

now, when i try to start it, no life. i tried it with two different batteries, no luck. charger is good, as it charges both batteries to full. i can only turn it on, when i take off the bottom lid and metalic shield. in that state, i flip it over plug the charger in and it turns on, chime, boot to system and stays there for however long i need it to. i put it together and no life...

i restarted PMU, tried CMD+alt+P+R, no luck... actually the second one seemed to get it a bit quieter, at least the chime did sound quiet.

it never was water damaged never dropped...

i also noticed, that the fan is not working, but spins when i put it on external powersource... i tried to install some fan control, but for some reason it does not allow me to run it...

can anybody help? thank you

I have tried suggested. Only partial success. Now it turns on every time. And every time after i log on i will get kernel panic. I wonder, does this shield also play any other role than being emi shield? If no, i believe if i put a heet of paper between shield and board, it should solve my problem. What do you think guys?