Re: no Spark.
There will be a voltage reading on the negative side of the coil if you measure from ground to that terminal. That is normal and means nearly nothing, only that the coil winding is passing the voltage from the positive terminal to the negative terminal as it should. The negative termninal connects to the points in the distributor which ground and unground the negative terminal, this produces the spark via an induced current from the primary coil circuit (positive and negative terminals) to the secondary coil circuit (spark plug wire going to the distributor). Both of the coil circuits ground thru the negative terminal.
A coil is really just an electrical step-up transformer. It is two sets of tightly wound wire in coils (imagine that!), one around the other in close proximity but not touching. The primary winding is what the positive and negative terminals connect to on each "end" of that winding, it is the only one with actual power applied to it. The other coil of wire, called the secondary coil, is what the spark plug wire from the distributor connects to. The secondary coil picks up voltage inductively from the primary coil but has way more windings so the net effect is way more voltage is produced but with less current. That is what goes out the coil tower and into the distributor for, well distrubution to the individual spark plug wires thru the rotor and distributor cap.
Under the covers even electronic ignitions work this way, they just use much more reliable methods to trigger the coil, and also increase the amount of voltage that comes out of the coil.
