Sprayer 12Volt Sprayer Question

[vacman]

Hello to all. I've lurked on this forum for a while but this will be my first post.

Last year I bought an inexpensive 25 Gal. sprayer from a local Farm store. It is a Master Manufacturing brand with a Delavan brand pump. In the fall, as I was running a tank of clean water through it, it stopped spraying. It had stopped before but after it would sit for a while I could get it to start again so I didn't give it much thought. Last weekend I pulled it out and tried to spray and no go. I read some posts here on this forum and used a suggestion of priming it by pumping the tank with compressed air. I'll be danged, but that worked like a charm. Periodically during my spraying project, it would stop spraying. Each time it stopped, I reprimed with air and back in business. I like the fact that the air compressor idea works, but I am annoyed that I have to do it more than once during a session. Does anyone have an idea why this situation is occurring? Any remedies? FWIW, I did take the pump apart and it seems OK. The pump is in fact running. All the hoses and the strainer are clean and clear.

Thanks in advance for your help.

 

[Furu]

Not familiar with that sprayer but your description makes me think you may have a vent problem on the tank. As you spray it draws liquid out and air should flow in to replace the volume through a vent. Often found in the cap but can be standalone. If the vent is inadequate or inoperative the vacuum is drawn and the pump can only pull against so much vacuum pressure. Eventually you cavitate the pump and no flow. Priming the pump and letting air into the tank and you start the cycle over.
If this is your problem it would most likely develop faster with a full tank than if you started with a tank only 25% full.

 

[Mike476]

I'd say you're exactly right, need to some way to replace the volume lost or you'll burn out your pump in a hurry

 

[vacman]

Well that was pretty quick. Thank you guys for that suggestion. The tank doesn't seem to have any vent. There is a small gap around the intake hose. There is also a small (under 1/4) hole in the cap. That hole usually has a rubber tether running through it but I removed that tether to insert the nozzle of my compressor. It may be too small even without the tether and that might be the issue. I could try to run it without a cap and see if there is any change.
Thanks again.