The first thing you should do is check your hoses for cracks and tighten the hose clamps. Especially the hose going from the pump to the tank. I’ve found loose hose clamps on mine before but I never had low pressure.

 

I have a 25 gal Fimco. Just bought it this year and it works great. On mine, there is a connection just before the pump. Inside that connection is a screen that prevents crud from getting into the pump. If yours has that connection, un screw it and see if that screen is plugged.
I’ve had pressure loss with the pump running and that screen was plugged with crud.

 

start taking hoses off and see if you have flow thru the pump or not

I got a new pump and upgraded the quality of the pump in the proccess, got a higher quality SUREflow from grainger and it's like a whole new unit

 

Hose issue or that screen, I forgot about the screen once and had no spray at all, after jacking with it for hours I called my cousin, first thing he said was did you check that screen...DUH!

O also had an issue at the pressure gauge once, but it was obvious.

 

I don't believe that the 15 gallon has that screen or a pressure gauge.

 

There is a screen on the pickup line inside the tank. If you leave chemical in there for any amount of time it will make a film and coat the screen. Easy fix. Pull hose off pump and out of tank. Spray water, or air through the hose backwards until screen is clean. Similar to this.

Sent from my SM-F721U using Tapatalk

 

There is a screen on the pickup line inside the tank. If you leave chemical in there for any amount of time it will make a film and coat the screen. Easy fix. Pull hose off pump and out of tank. Spray water, or air through the hose backwards until screen is clean. Similar to this. View attachment 7915945

Sent from my SM-F721U using Tapatalk

Winner winner chicken dinner ha. That worked!! Running like new. The hole where the hose connects to the tank was plugged with junk. Thank you !!

 

A pump creates a vacuum to move liquid. Suction then discharge. Spray shaving cream around the suction side fittings. If it sucks the shaving cream in, you are sucking air and the pump is not able to pick up the liquid. If it doesn’t have a leak, check the suction line. If it’s clear, pull the pump apart and check the impeller.

 

I have that exact sprayer and it did that when I didn't have the valves set right between the boom and wand. Mine has to be close to 20 years old.