Fixing genesis carts

Okay, i bought Zoop from Funcoland and recieved Kid Chameleon from a friend...neither cart "works". Both show the "Produced by or under license from Sega Enterprises, LTD" screen, but go directly to a black screen after that. I cleaned both carts with "Goo Gone" (citrus stuff, works wonders for cleaning fact, kid chameleon would only show the first screen after being cleaned) and they still do not work. Anyone have any suggestions, or are they both fried?

p.s. kid chameleon was tested on a genesis 1,2 and nomad. zoop was tested on the genesis 1 + nomad.
The fact that the "PRODUCED BY..." screen appears shows that the Genesis is able to read the ROM header, so that's something, at least.

I think more cleaning is in order, and I would personally recommend using Isopropyl alcohol rather than anything citrus-based. Soak a cotton bud (Q-tip) in the alcohol and clean both sides of the cartridge edge connector from end to end.

If you still have no joy after another thorough cleaning, you might want to open up the cartridges and check for damaged traces or dry solder joints. It depends on how much time you have on your hands, really :

I tried cleaning them (exactly how you suggested) and the contacts are so clean i could eat off them (if i were eating a very very small meal) but they still just show the "PRODUCED BY.." screen. When i can get a gamebit screwdriver i'll open them up but until then i'll keep filing down this flathead...FOR KID CHAMELEON!!!!