The truck will randomly have a long crank time at startup. 90% of the time it starts on the first or 2nd revolution. But lately it will randomly crank for about 5 seconds and then fire with a minimal amount of smoke.

The truck runs flawlessly once it starts. It starts perfectly when cold. Truck has 131500 miles. Fuel filter changed 3k miles ago. The TST/mp8 on or off makes no difference it seems.

 

I've read that is a sign of excess fuel return. Maybe an injector is going out? I'm no expert, just a guess.