Thanks both for your replies.
I am positive that there was water in the tank. I had added water myself this through the fill port and could see that it was at least half full. What I meant was that I am pretty sure that on a previous trip the tank became full, but I don't recall putting water in it. It may have filled itself due to a check valve issue. That only happened once. Just added that statement to fill in the whole picture.
When pump was operating "half power", I could hear that it sounded different, it wasn't as loud and it pulsed more, and the water didn't come out with as much pressure.
Now the pump runs constantly when turned on, but it isn't as loud as when it was operating at full pressure (that's what I meant...lower volume noise). But no water output.
Water works perfectly fine when hooked up to city water supply.
I will check the suction strainer. I need to look that one up, though. Can you tell me where it is to save me some time?
Thanks again for your help.
2015 Shamrock 233S
2007 Ford Expedition EL Eddie Bauer
2016 Nights Camped = 22