my 2003 sprinter wont startin morning without starting fluid. it will start after that

 

If it will start with fluid, the fuelrail pressure is not getting high enough to allow a signal to the ECU to say ALL OK TO START. It could be too low of pressure for the following reasons:
1 Starter is worn not getting enough speed to reach pressure,
2. Battery is too low to allow fast enough starter speed
3. 1 or more injectors is worn/plugged and letting pressure backflow
4. An O-ring on the fuelrail pressure valve is leaking
5. the fuel filter is clogged.
Use of Starting fluid must be minimal! It does speed up the engine's pumps, but because it ignites before Deisel it may ignite before the valves are closed and send a valve thru your pistons, or blow out your intake manifold.
Use as little of the starting fluid as possible and at your own risk of damage to the engine. I've needed it before and never needed more than 1/2 second of spray into the EGR to start.
Are there bubbles in the clear fuel lines in the morning, if so the O-rings on the fuel filter may have shrunk allowing air in.

I would to an injector leak-off test, use Diesel Kleen injector cleaner, change the fuel filter, bench test the battery at an Auto parts store etc