I noticed today that my truck was missing really bad so threw a timing light on it. While goin through making sure all the plugs were gettin spark I heard an arching sound. I noticed that an arch jumpin from the coil wire to the vacumn hose. I am already replacing the the plugs, plug wires cap and rotor tomorrow after church and rapped the vacumn hose in electrical tape to hold it off for now. But im curious what would cause this???? The hose is rubber so it shouldnt conduct electricity??

Thanks in advance Josh

 

Why did you wrap the hose and not the coil wire?

I don't understand how the rubber vacuum hose is acting as ground either.

 

its something about the carbon in the vacuum hose. I was taught to use a piece of vacuum hose when doing a power-balance test of computerized ignition because there is just enough carbon to give a path for the arc to not damage any of the ignition. not too sure about anything exact, but the best explanation i have.

then of course its possible there is juat something conductive that got onto that vacuum line.

 

Your ignition wires are leaking...as a side note, see here how vacuum hose is used to check spark..Part 3 -Ford Ignition Module Test. Fender Mounted Module (ICM).

yep, not a problem with replacement rubber hose

 

I forgot to mention that I out some on it to.

And thanks for the answers! definetly answered my queston.

Thanks Josh