Disc is not spinning with a new laser PlayStation 2

aspi91, "this trying to start spinning but not wanted to spin with the new laser on." and "I took the old laser off, and old one back, and the disc started to spin, but not reading" this sounds like your new laser assembly is shortening out the drive. Since you still have the old laser which sounds like it has failed, you may have to replace the laser assembly once more. Of course it is also possible that your height adjustment is off and the new laser assembly is blocking the drive from spinning up. So check on that as well. Since you still have the old laser and the disk spins with that, measure the height on the assembly and adjust the new one accordingly. On the old laser assembly you could of course also try to adjust the pots for the laser output. This usually requires an oscilloscope but can also be achieved with a good multimeter. The attached picture shows where those pots are. Turn clockwise to increase power and counterclockwise to decrease power. Don't turn those blindly since that may kill your laser using to much power or just not getting them back to work. Normal values are 800mV peak to peak (650-1000 ohms) with DVD and 640mV (950-1200 ohms) peak to peak with CD media.

For the pot adjustment with a multimeter in ohms check between these points.

To ensure the height is properly adjusted use the values from the old laser unit. Measure the height at the marked point using a depth gauge (vernier calipers have those)

you can adjust the height via the Torx screw bottom left in the image.