Truck Repair: 6.0 Liter Hard Start, injector nozzles, fuel quality

Question
I have an '06 6.0L F-350 with 97k miles. About 2 weeks ago it began having hard starts. If left for long hours, it tends to start (a bit of a long start but will eventually start.) The real problem is after a short period of driving after it has been turned off it won't start without ether. I replaced both batteries and the fuel filters with no effect. There are no fault codes. The air filter appears clean. Any advice would be much appreciated. Thank you in advance.

Answer
Hi Mark,
Hard starting can occur due to a variety of reasons among which are:
1. Poor fuel quality
2. Air in fuel system
3. Malfunctioning non fuel return check valve on the fuel return line to drain
4. Malfunctioning injector nozzles
5. Malfunctioning fuel solenoids due to partial or intermittent contact
6. Worn out fuel pump elements.
Try to verify all of the above and perhaps you may find a solution therein.

Kind regards,