turns over but won't start

To start with I have worked on cars for 40plus years. With that being said, I installed a water pump on my 1996 Dodge ram 4 wheel, withair. 5.9 cu. in. After I installed water pump, got everything together the truck turned over but refuses to start. I might add I removed the fan and installed electric fans, but they are wired directly to battery so should have no bearing on the no start problem.It has myself and my friends baffled.