Perhaps you're fluid lines are blocked. There is a screen on the solenoid that attaches to the rack and pinion - if they took the solenoid from the old rack and reused it on the new one, it's possible it was not cleaned first. There is also a screen in the pump reservoir which has a tendency to get blocked. Often, when the pump is replaced, the reservoir from the old pump is reused. It's also possible you're replacement pump is bad.