Water Pump won't prime, suggestions?

Golden_HVAC wrote:
A new pump will solve the problem. A pump rebuild kit takes about 10 minutes to install (about the time to install the new pump) and only cost about $18.
Try the pump kit first. IT will likely solve the problem.
Fred.

Thanks, Fred! I went to an RV store and asked for a rebuild kit. The guy asked what the problem was. When I said it worked well except on priming, he pointed to the Shur Flow valve replacement, just one complicated rubber piece, for $28 CDN. I had a photo of my pump and he made sure it was the right part.

I unhooked my pump (only a couple of spoonfuls of water fell out of the pipe), opened it up and found the original "valve" looked great except for a few fragments of pipe cuttings in its grooves. The "membrane", a stiffer piece of rubber like material behind the valve looked good, too. The pump primes way better with the new valve. My tank is a foot or so below the pump and in the past primed itself only when parked on a slope to reduce that foot of height and filled the tank to overflowing. This time it self primed when level and the tank half full.

The job called for some attention to which screws go where because there are two kinds of them, course and fine threads. I recommend avoiding the temptation to take the back end of the motor housing off to look at the brushes - I had to ask for help to get it back on! The trick is to stick wires or long needles into the little holes in the plastic brush holders to hold the springs and brushes in place while putting the back end on. Tricky to get the bearing end on the shaft because it is free to tilt. My 11 year old brushes were still in great shape. No carbon in the commutator slots.

YouTube video helpful on Opening the pump: Youtube
The video refers to the black Shur flow valve as the diaphragm. The yellow/white part behind it is what Shurflow calls the diaphragm.