Truck Repair: 1995 n14, leaky injector, check fuel

Question
i have a 95 n14 and have a hard time to start it in the morning (have to turn it over for 10-15 sec. before it fires) i replaced the check fuel checkvalve already did not help at all it.runs good ones it runs, sometimes it is hard to start even when it is warm after shutting it of for 5 min. could it be a leaky injector? how would i know which one? please help

Answer
Does it have a fuel filter on the pump?if so is it the Fleetguard FS1000?The Fleetguard has a tube made in it to help with starting.Probably not a inj because it would smoke badly on start up.Sounds like it is just draining back but I would check the check valve for debris.