ok, i have searched... and read a lot in an attempt to fix.
i have a pioneer head unit, and a mtx amp for the sub, and a sony for the speakers. everything sounds awsome with the truck off. but when you start it up... well you can hear the fuel pump, and there is MAD sound tach.
i have pluged the rcas into my ipod, and it plays great with the truck running, no noise or anything. both amps have 2awg to the frame. and 4awg from the batt. the batt is an optima redtop so it has the top posts, and side posts. i put a 2awg from the side post to the frame. and the top post ground goes to the body with about 12awg, and to the block with 2awg. all the grounds on the body, frame, and ground bolts i just cleaned with a wire brush with my grinder.
no here is how the head unit is wired. i have an aux fuse box which i have some aux lights wired in and that kinda thing... it has 8awg to the batt. my stock fues box has about 10awg, and the starter is 2awg. this is all on the top post, and both amps are hooked to the side terminal on the batt. (the top + post cable has all thoes cables molded into the connecter like this link! )
so the deck is wired to the Aux fuse box with 12awg wire and it is switched on with a toggle and the toggle gets its power from the same 12v line. then it grounds to the body in the cab. now im 90% sure that the ground problem is at the deck.
i tried hooking some jumper cables to the ground post on the batt and un hooking the decks ground from the body, and clamping the jumper cable to the decks ground, and the chasses of the deck. it made it a bit quieter but not much. i also tried my older deck and it too had sound tach, and fuel pump noise.
i get the noise in both amps. all my speakers are amp powered. when i play my ipod threw the rcas it sounds good.
how do i get rid of the noise? im out of ideas... so i guess im gunna buy a ground loop isolater. and see what that does. any ideas?
its grounded behind the dash using a self taping screw.... i have also tried to ground rite to the batt and it still does it. its an older truck... and the ign is screwy, i like having it on a toggle.
the noise has to be from the radio.... you already isolated that by having the ipod eliminate it & give a clean signal.... I would rip the radio out of the dash, take it in the back & ground it to the amp wire & power it from the amp wire... if you still have the noise I would put the radio on the ground & run it over... another alternative would be to put it on the roof & then go out for a blast, but this could scratch your car & maybe cause damage to another vehicle depending on where it fell..... target practice could be an option if your into that sort of thing, then theres always ebay
if the noise goes away with the head unit in the back by the amps then there's a wiring problem....
well i tried hookin the deck up with the amp.. and it was still there. but when i hooked my older deck up with the amp it was gone so i think im off to get a new deck. ill see how this works out. thanks.
Ahhh, first example of a deck with burned ground traces!!! I made mention of this in the FAQ. It can be fixed by an electronic repair shop but its the WORST thing to troubleshoot! Good job turbo!