96 tahoe starting problem

My Tahoe (4x4 Vortec 5.7) will not start in the mornings when temp below 32 degrees. I have to shot it with starting fuild.
I have replaceed fuel pressure reg, plugs, wires fuel filter.
Does anyone know if there is some sort of sensor that causes this problem,
It will start when it is warm out, but takes three times.

Thanks.