With the key on you should have 12 volts between the + side of the coil and ground. I think the pressure switch just turns on the LP fuel lock valve and the hour meter. If you have 12 volts on the + coil terminal, then check voltage between the other coil terminal (-) that goes to the distributor and ground while cranking the motor. It should be fluctuating between 12 and 0 volts as you crank. If it stays at 12 volts the points aren't closing due to gap or they are not clean or the wire is broken from the coil to the distributor. If it is 0 volts all the time while cranking then the wire is shorted to ground somewhere like where it connects to the points and condenser in the distributor.