'04 Sprinter won't start sometimes

My son has a '04 Sprinter 158'wb, high roof, cargo, with about 325,000 miles. Whenever it feels like it, after the van is up to operating temperature, if you shut it off, lets say to make a delivery, then try to restart, the engine will turn over, but will not start, after a few trys at this, waiting a few minutes in between, it will finally start. I happened to be at the same place he was today when it did this, I thought it kind of sounded like a gasoline engine that is out of time, ie. the speed in which it turned over varied, like it almost starts, although he did not hear that. When it finally starts it will start like normal, and run fine, there seems to be no drivability issues, no check engine light. Any ideas, it can be difficult and expensive, and time consuming for a mechanic to fix, when it is an intermittent problem, unless it happens to do it for him.

The first step is to see if there are any error codes. Since the codes are stored, you'll see them after the fact.

Check the error codes first. But I bet this problem turns out to be that the injectors are leaking. Want to test that idea? Just spray some diesel into the intake manifold and see if she fires up. Do not use starting fluid! If she fires up and stays running you have ruled out most of the electrical problems that can happen. If see does not it maybe time to check the fuel filter, cam position sensor, crank position sensor fuel pump relay and the list goes on. I will post a link on how to test the injectors for leaks as soon as I find it. Hope this helps, Wayne

Here is the thread be sure to read the whole thing. This started out with one that had a problem when cold but there are also some that had a problem when warm. Wayne

https://sprinter-source.com/forums/showthread.php?t=9663&highlight=leak+test