Bad ground or bad turn on?

Hey. I've got a sony 600 watt 4 channel amp, and I can't seem to find a good ground for it. I've tried several places where there are already screws going into the body. I ground all of those places down to bare metal, and screwed the screw in as far as I could without breaking it, but the ground still doesn't seem good. The amp acts sort of funny...sometimes, the amp will come on, and everything works great, but then I'll start driving and it cuts off. Or, it will turn on, and then I'll shut the car off, and start it up again, but the amp won't cut on. I know I've made a good connection for the amp turn on, so I don't think that's it...but then again, I really don't know. So, what do you guys think? Does it sound like a ground issue, or something fishy with the turn-on lead? Thanks.

try testing the remote turn on with a test light, that will be easy and will either eliminate the problem there, or you need to bench test that amp. have you tried putting the ground to something like the strut tower bolts? hey even more detail on this topic exists in the ground Q&A froum you may want to consult with that!

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Is it possible that the remote turn on wire is too long? I haven't yet cut it down to the right size, since I was just testing the amps operation...

to make a good ground, take a foot or so of 0AWG wire, with ring terminals on both ends, get a couple 1/4 inch bolts,nuts, and washers. Drill a hole in your frame under the car/truck. Use a wire wheel, and take the area around the hole down to bare metal. Bolt one side to the frame....then take the other side, to your trunk area or wherever you want your ground. Drill a hole there.. grind down the area of all paint...insert the bolt  and attach your ground cable inside the car and tighten...if you have access to a welder, you can weld the connections in, but if you dont know how to weld i wouldnt recommend it.

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ok...listen to this. I got out my multimeter and tested the terminals on the amp. The amp is getting power, because connecting to the 12volt constant and the ground produces 12 volts. So, I tried connecting a larger gauge wire to the remote turn on at the head unit, and still nothing. I checked all the fuses, and they're all fine. The only thing I can figure is that there is something wrong with the amp itself. For some reason the amp isn't getting the power from the turn on lead. Any ideas? Thanks

nm everyone...The light actually WAS on, but from the front seat, I couldn't see it. and as for the sub not working, one of it's wires came loose when I was driving. Sorry for wasting everyones time. Thanks, though.