Electrical Interference

[maroman88]

the blazer has an interference sound in the stereo and any 2-way radios in the truck, only when the engine is running running, never with just the ignition on or off all together. So i assume its related to the ignition? i checked all the plug wires, none appear damaged or to be close to any other wires... any other thoughts?

[Stevoone]

Does the noise increase in pitch when you step on the gas? I had an issue with an alternator in my brothers old car. Try running the engine with the alternator disconnected. I don't remember the name of it but I found an electronic noise filter that I installed in the battery cable to the alternator, never heard the noise again.

Could also be ignition related but I thought that was with older style ignition systems.

[sweetbmxrider]

Probably something to do with the grounds. They make ground loop isolators to prevent the backfeeding buzz. I'm not sure if they make one for your particular setup though.

[maroman88]

does not increase with engine speed... prob is a ground, i never noticed it until after the new engone was installed

[maroman88]

guna correct my last statement, i noticed it DOES increase with RPM

[maroman88]

well it got worse, i thought maybe it could be a bad ignition wire, so i replaced them and the spark plugs, while replacing i noticed some cracks in the cap of the dizzy, so i replaced the cap and rotor (man the originals were nasty!) and now the interferance noise is gone

[greenformula92]

maroman i was going to suggest the cap. everything is so tight knit under that hood that any electrical interference with the ignition system back there can effect the radio. You're not the first person I've heard complain about that in a blazer