Needing to purge air to start each time after elec. lift pump install

You can install a check valve but shouldn't have to, Is the return line from the fuel filter to the #1 injector hooked up? A little more info on whats happening would help.

Your electric pump is down on the frame just in front of the tank selector valve correct? If your return line from the filter head is hooked up there should be no reason to purge anything. What are the rest of your problems? Do you still have the lift pump hooked in line using the electric pump?

How long since you have replaced the return lines, tees and o-rings? After you get all the injector tops clean and dry and you drive it is there any wetness around the fuel return line tee's. If there is get a return line kit (can be found for about $25 online) . Check the fuel priming valve (looks like tire valve) on the filter head, if its missing it put a good quality cap on it. You didn't say if your lift pump is still hooked up. If it is and your using an electric pump having the lift pump still inline is a real bad ideal. If the diaphragm on the lift pump ruptures the electric pump will fill your crankcase full of diesel fuel in a short amount of time. If your electric pump is working right it should fill your filter and push any air out through the return line in less time than it takes your glow plugs to cycle.

I would check fuel pressure 4-6 lbs should be good, Has the pump timing been messed with, and how about has the fuel been turned up.Does the truck ever black smoke.