Blocked (partial) line or sprayer. Remove tube from sprayer head and pump some fluid, if it increases volume you have a clogged sprayer use a pin or air to blow the sprayer in reverse. If fluid does not come out of tube with volume and or pressure then back blow lines. Ten to one odds you have crud in the lines or in the ww fluid pump unit. Back blowing with low pressure air could and should rectify the situation. I did say low pressure air like below 20 PSI. Pajero had a similiar problem I had to disassemble the pump and clean crud out of tank and impellor
"Why are some peoples mouths in overdrive but their minds are in neutral"