Greg: The 1000 fires from a "short" across the START pair. You can pick it up on J19 inside the unit or on the rear CPC connector. Most common cause of not firing is a bad/loose connection between the board with the firing relay and the two terminals listed. You can start from either end but just short across the two wires and work back unitl it either starts to fire or stops firing (depending on which end you start from). If it fires all the way back to the relay card it has to be at that card (considering you stated the relay is firing) which you can hear.
The 1000 is a real reliable workhorse. I assume this is a machine torch that will fire from the START Pair. If you have a hand torch with the torch switch tapped into then that area should be carefully checked.