Moved water pump...now it's acting strange!

Is the pump at the same vertical height as it was before? Some pumps have pressue to push water at high pressure but not enough suction to draw water up into it. Lookng at large scale pumps like well pumps. They can draw water from deep wells of hundreds of feet and push out under pressure but other large pumps like ditch pumps can only raise water a very few feet but can push it out under high pressure. Since most pumps I have seen in RVs seem to be mounted almost level with the bottom of the tank I suspect they can push water out with pressure but limited to how far they can raise water into the inlet of the pump. Seems to me if you just added extra water line and didn't raise the pump vertically it should operate the same providing there are no leaks in the fittings or water line