91 Dodge Caravan won't start

Ok, here is my problem. We just put in a new head gasket yesterday but now the van won't start. It sounds like it is trying to start but just won't turn over. We know there is spark, and we know it is getting gas (cause of the smell) anyone know why it won't turn over???

Wondering if we have the spark plug wires on wrong, We put them on according to the layout in the Haynes manual.

Any help would be wonderful.

Luna