Is it smoking while you crank?
Are you sure all of the new glow plugs are getting 12 VDC? Is the fuse on the firewall blown? Did the PO fab up individual wires for the plugs? Sounds like you have fuel to all injectors but lacking heat enough on a cold morning to make it go bang. With a tight belt I wouldn't expect poor timing as it was running fine previously. Blow a gasket maybe?
What's the outdoor temperature? Is it cranking slow /fast?