This was a curious problem that I had recently.I decided to relocate my msd 6a
box,and reroute some fuel lines.The car was running fine before I did the work,
no electrical connections were altered from where they originated or where they
terminated,the wiring was either shortened or lengthend for the new location of the msd box.So I double checked all my work as I went along so I knew the wiring was all ok,and the dizzy was'nt touched at all.I finished the job,hooked the battery back up,hit the key,and no start.It would crank and crank,but would'nt fire.So my first obvious thought was the wiring,pulled it back out,checked for proper voltage,all ok there.Then I ran all the tests that msd say
to use, to verify proper operation of the box,that too was ok.I was starting to wonder what was going on,so on to the dizzy,checked the pickup,ok as well,so I pulled the dizzy out,and redid tdc on #1 cylinder just to rule that out,but still no go.I checked for spark,got nothing there,then put in a new set of plugs,as the other ones were fouled,still nothing.So after spending most of the day wasting my time,I gave up and went to bed.The next day,I went through everything again just to make sure,but it still would'nt fire.Then
I remembered that I had a spare coil laying around,so I tried that and bingo,
away it went,running just fine.Did'nt I feel stupid.Sorry for the long post,just shows that it can be something simple that gets overlooked,and it becomes frustrating and you end up doing a lot of things that are'nt neccessary.
Maybe this may help someone else.

Alicat.