We had dozens of these where I used to work. I've run into the problem with the pump relay occasionally not sending voltage to the pump many times over the years. Often it is from carbon building up on the relay points.
Something you can try is:
A) Ensure that the power is turned off to the entire system
B) Using a strip of very fine emery cloth, perhaps 1,000 grit, gently slide the cloth across the relay points. Slide a few times, turn the paper upside down and slide across the other points.
C) Use Contact Cleaner to clean the debris off of the points. (Option: Dip a piece of writing paper in alcohol and slide it through)
D) Blow air around where the metal plate with the points pivots. Sometimes dust settles there.
E) When the contact cleaner or alcohol is evaporated, turn power back on to the unit.
I hope this helps and saves you some frustration and money!
Paul
PS: To be honest, I removed mine at home and replaced it with an aquastat and a couple of ice cube relays in an appropriate enclosure. But, that will involve a lot of re-wiring for you. Hopefully you can get the L8148 working well.
