Does anyone know what the capacitor that comes off the coil wire does?..The dealer told me its called a radial Capacitor but what does this thing do?The truck is a 95 f 250 with a 351w.

 

Probably there for supressing ignition noise in the radio. Caps were used on the old ignition systems (the ones with mechanical points) to reduce arcing and pitting of the points. As used today they are usually for noise suppresion, or in the audio world HUGE ones are used at the amp "to prevent voltage droop". Dubious in my mind, but then what do I know.

 

Capacitors are like short term batteries, They hold a charge for a certain time period!! Before working on certain circuits, short out a cap with a screwdriver across the terminals, Or else it will dump all it's current into you with a quickness!! A cap has barely any internal resistance unlike a battery so when you make contact with the terminals it transmits all the energy, that is why they are dangerous until discharged even low voltage ones!! Putting one across your battery will help smooth out the power from the alternator, It really isn't true dc coming from the alternator but a pulsing dc. If you have noise on your cb or radio putting a big cap on the battery will help smooth out the current!! Get a cap and charge it up and short it out, It releases so much energy so quick, I can feel it in my teeth when it sparks(don't put on your tongue!!) Those throw away cameras have a killer cap in them, If you are careful take apart the camera (don't worry the film rolls into the case you won't expose it) pull the battery out, Discharge the big cap in there with a insulated screw driver(if it hasn't been used lately it it probably won't have any juice). figure out a way to insulate the electronics(plastic battery case) and put the battery back in, charge the cap by hitting the flash button, and get ready for some fireworks, short out the terminals!! That is some power right there boy!! It will kill you if your not careful!! Always keep your left hand in your pocket when working with high voltage!! The veins in your left arm go straight to your heart so a shock to it, Has a higher potential to kill you!!!! Those flash units are nice little toys you can set them up as booby traps solder a new switch with longer wires and put the electronics in a case an old rayovac battery package works good for a project box. Run the switch to whatever you want to protect, if someone moves the object and the switch gets tripped it will set off the flash!! Making them think they just got their picture taken!! I made a crazy DIY disco ball with 10 of them, I made it so the switches were activated by a cam on the center shaft of the ball when it spun the flashes lit up. It was just one of those things to do just because. My sister worked at the photo center and would bring home piles of them for me.

 

The one coming off of the coil wire is for ignition noise supression. It acts as a low-pass filter; so any high frequency spikes generated by the coil pulses are "shorted" to ground (as the frequency of a voltage signal across the capacitor increases, the impedance of the capacitor decreases).

 

And your engine will run just fine without it. However, you'll be more likely to get noise through your (and adjacent vehicle's) audio system, especially if on the AM band.

Steve