I am trying to diagnose whether or not my timing chain has slipped. I have a 1986 F-150 with a TFI-IV ignition system. The motor will turn over, the plugs are receiving fuel and a spark, but will not start. I have manually rotated the crankshaft approximately 10 times. I realize that with properly timed motors, when the rotor is pointing at the number one spark plug wire terminal in the distributor cap and the zero degree timing marks are aligned, the number one piston is at TDC on the compression stroke. However, when aligned as just described, the rotor points to the number two plug in the firing order. Also, my timing chain is showing 18-19 drgrees of excess play when I test for excessive chain movement. Are these symtoms of a timing chain that has slipped and would this cause the vehicle not to start at all?