I have an early 99 F350 w/ 7.3L Powerstroke. I assume yours is the same. You didn't say. I have had my truck since March. It has 197K on it. Starts like a charm. It sounds to me as if the glow plugs are getting weak. But its warm out so that may not be it at all. The other direction would be the high pressure pump output. perhaps the fuel filter is clogged. Its on top of the engine in the valley. In order for these engines to start they need to produce high enough pressure in the High press pump to inject fuel into the cylinders. So you turn on the ign. which starts the electric fuel pump between the tank and engine (among other things). This feeds the high pressure pump which is mechanically connected to the crankshaft. It will not work until the engine is turning over fast enough to produce the need psi.
I learned tons on these trucks by this website and also POWERSTROKEHELP.COM - The Information Source for Ford Power Stroke Diesel Owners & Mechanics and Home of EDAS® "Engine Damage Avoidance System" for Powerstroke Diesel Trucks
some folks on here don't like this guy but I found the videos he has very enlightening.
A diesel will never start like a gasser. A full fuel filter canister does not mean the delivery is right. Take off the inlet line and put it in a jar or something then turn on the key to see if the flow is good. Its a very rough test but would give you an idea of how much fuel is being delivered to the hpop. Mine turns over for a 2-3 seconds before it starts every time. Never will it be like a gasser that seems to start with just a touch on the starter. Its just how a diesel works.
I just reread your original post 10- 15 seconds is way too long. If its your hpop its going to be big $'s.
If you are a do-it-yourselfer then I suggest this
POWERSTROKEHELP.COM - The Information Source for Ford Power Stroke Diesel Owners
He sells videos on what to look for in no start situation. IF/When I have trouble with my truck I am going to start here
Ok let's see here first I thought that fuel pumps are cam driven not crank driven and the 7.3l and 6.0 use heui injection which is oil runs through electronic injectors. So with that also with the glow plugs they are not going to affect your starting unless its cold your thinking an idi such has a pre combustion chamber and need glow plugs. You said when it does start there is no smoke hmmm how is your oil if its clogged it will take injectors a long time to fire and codes popping also which light are you talking bout that goes out comes on and goes out come on again
Pull your icp sensor and see if it starts and runs better also check and see if there us oil on the plug
OK, first off, the fuel pump on the rail, electrically driven, not crank driven; of the truck provides around 50-60 psi of fuel to the fuel bowl, on top pf the engine, and it has a regulatoor on the return line back to the tank.....
the low pressure(engine) oil pump) is crank driven, and provides oil for the engine and the resivior of the high pressure pump.
the HPOP(high pres. pump) provides 500 PSI of cranking oil pressure to the injector plungers to open them up to fire fuel into the cylinders. when running and under load, the HPOP provides 2000-3000PSI of pressure to the injectors.
pull the ICP wire plug, on the drivers side front of the head, and see if it runs. its a sensor thats screwed into the top of the front of the head. white plug. you can unscrew it and see if theres oil in it... could be IPR, which is the regulator for the HPOP. if its stuck closed it wont open.
how is your fuel filter? needs to be changed at least every 10k miles. I do mine on every oil change. (5k)
you can unscrew the fuel bowl top, and either drain out the fuel in it by the yellow handled valve on the back of it or by sucking fuel out of it. put top on, and cycle key. see if the pump fills the bowl.
thats a good place to start...