Priming problems with jet pump

I have a 2 year old het pump with about 70 feet of line on a gentle but continuous slope to the lake- the foot valve is also just 2 years old. When I remove the plug to prime the pump it appears to fill. I then recap and turn on the pump but the pressure won't build and hold. We examined the foot valve under water and it appears to be working properly. I have 2 questions - there is a shut off between the pump and the main line to the cottage - should it be open or closed on initial startup? Also, I saw somewhere where it was suggested that you leave the plug out and continue to run water into the pump until you hear the motor running smoothly and prime is being held. Is this recommended? Any other suggestions?

Make sure the pump is full of water and the main valve is off on the discharge end of the pump. Leave the plug on loose to allow air to escape. Once the pump is primed the pressure will build and you will have water shooting out where the loose plug is. Tighten the plug and slowly open the main valve half way with a hose running to allow all the air to escape. Once you get a steady flow rate, You should be able to open it all the way but do it slowly.

Sammy

How to prime a pump:
You need a gallon jug of drinking water, teflon tape and a wrench.
As stated, turn off any valves/hydrants on the discharge side, and turn off or unplug the pump.
1. Wrap teflon tape clockwise only on the threads of the largest plug on the pump head (usually 3/4") as the threaded end faces you.
2. Fill the pump head with water, turn on (or plug in) the pump and quickly begin hand-tightening the plug. Water and air will bubble out around the plug, but that's normal. Hand tighten the plug and let the pump run until it picks up prime.
3. Once the pump picks up prime, tighten the plug with the wrench.
If it doesn't pick up prime, keep repeating the steps, including new teflon tape, until it does.
Good Luck!
Mike