Audio Systems: no volume from cd player, pioneer sterio, connected drive

Question
"i have fitted in a pioneer sterio into my car which works fine, until
i go over a bump, then the volume cuts out, although the cd is still
playing. i then put my cd in to see if the volume works again and still
the cd plays but no volume. then if i turn my engine off and on again
the volume comes back on but only sometimes this does not always work.

Has anyone got any ideas on what the hell is going on is my cd player
faulty or is it a cable. if a cable has come loose i cant understand ehy
it plays when i turn the engine on again sometimes????"  

Answer
sounds like you have a wire that's getting grounded against metal somewhere.  maybe a door speaker wire inside the door or something. anyway what's probably happening is that when it shorts out, the amplifier inside the cd player goes into protect mode. the reason it starts working again when you shut the car off is because this resets the protection to "try again".  
again, this is a guess so far.   but it's about all I got for now.  
as for fixing this.  I'd pull out the cd player and disconnect the 4 wires going to the front speakers. leave the rears connected.  drive around for a while and see if the problem still occurs. if the problem goes away then the front door speaker wires were the fault.  you can hook up just the left or right and continue the test until you find the speaker wire that causes the problem.
if disconnecting the fronts doesn't fix the problem, then reconnect the fronts and disconnect the rears and drive around for a while again and see if the problem goes away.

let me know how that goes and we'll work from there.

good luck!