Engine interference in CB and AM radio
 

I drive a 2004 Mack Granite. Whenever the engine is under load and you have the pedal most of the way down, there is buzzing in the CB. It's not the antennas or the cables because it also happens on the seperate AM/FM radio as well(AM band only). Both the CB power outlet and the AM/FM radio share the same fuse and I wonder if a filter could be installed.
Could the electrical interference be caused by the injectors being pulsed?

Re: Engine interference in CB and AM radio
 

Sounds like you have a wire or component generating unwanted noise. The best way to find the source is to use a small, cheap pocket-type AM or AM/FM radio. Turn it on AM and tune it so it's not really receiving any station on am and all you have is static. Then, lower the antenna till its almost all the way retracted. Now, using the antenna stub as a pointer, move from wire to wire, component to component under the hood. When you get close to the offending item, you will hear the engine noise through the radio's speaker. For BEST results, use headphones if you can as this makes it a LOT easier and will be more accurate. Once the offending wire or component is located, you can either fix what's wrong with it (usually a poor ground if it's a component or if it's a wire, it may be cracked or broken INSIDE of it's insulating cover and you can't see it) now you can replace it, or you can install a filter at that pointand you won't need a filter for everything ELSE on the truck.

Items to check: Alternator, fan (if electrically powered), ac/heater blower motor(s), the injectors, and any other electric pumps or motors.

Also check ALL ground wires. ESPECIALLY the battery. Make sure they are TIGHT, corrosion free and at the point they are grounded to, make sure there is NOTHING between the connection (wire) and the base metal surface.

Re: Engine interference in CB and AM radio
 

Sounds like you have a wire or component generating unwanted noise. The best way to find the source is to use a small, cheap pocket-type AM or AM/FM radio.

I actually used this trick to find a bad spark plug wire that the GM technicians couldn't locate on my Chevy truck. The problem is that the Mack engine has to be driving under load. Does not make interference noise in neutral.

I'm guessing Alternator or Ground-You can get a filter for that noise.

Re: Engine interference in CB and AM radio
 

Hmmmm... That makes my idea a little dangerous then hehehe

When under load, it's POSSIBLE something is moving and causing a bad ground situation. To imagine what I'm saying, remember how any motor vehicle twists and bends when you rev the engine up and down at a stop light. It's plausible that a wire mounted to the chassis or a frame member is tight when you inspect it at a standstill, but loosens up when the metal surface it is attatched to moves away or to it when the engine torque is tweaking the frame.