Holden205

I recently replaced the timing chain and gears on a 98 blazer 4.3l. Afterward, I have no spark. Is it possible for the crankshaft position reluctor gear to be installed backwards so as to prevent the 4 volt signal to the ecm? I replaced the position sensor and connected a volt meter to the signal wire and barred over the engine. I don't get any voltage change from the constant .04 volts static. When I look into the position sensor mounting hole, I can only see half of the reluctor gear in the opening. Is it possible i installed it backwards? I'm asking before tearing open the time cover, along with everything else in front of it.