Sounds like air in the lines, but this will be almost impossible to diagnose without more information on the equipment.
Even I sometimes struggle with pumps and unloaders/regulators. After spending nearly 20 years as a distributor sales and service rep, with all that factory and hard knocks
training, and mentoring from some of the best and experienced cohorts in the biz…even I have:
Rebuilt a perfectly operational pump
Replaced a normally operating unloader
Tightened a perfectly tensioned belt
Replaced a relatively new spray tip
Reused a threaded fitting without first removing that big ‘ol wad of Teflon tape on the shoulder.
Just last week I investigated a report of “low pressure” from one of my regular customers. He was right! The pressure was down about 150psi. I immediately replaced the obviously worn spray tip. When that didn’t remedy the problem, I lowered and raised the unloader several times…to no avail. In fact, that made the issue worse, so I replaced the unloader with a “new” regulator which required a slight change in the plumbing. Still no change!
Belt tension? Check.
Weep check valve leaking? Nope!
Water supply good? Yep!
Time for a pump rebuild?
Well, it is the busiest bay…and even though the pump is only 3 years old…what else could it be? So, in go the new seals (yeah, they were a bit “iffy”). Crank it up and now it maxes out at about 700psi!?! Ten minutes of head-scratching and muttering were followed by swapping a regulator from a properly working pump. TaDa! That “New Looking” regulator refused to play nice! I must admit to using some foul language.
Now, it’s time to work on a second pump…original to the car wash…maybe 28 years old and with no record of maintenance. It too was down on pressure, and pulsating. The seal cases were loose, the high pressure seals came out in pieces, and the low pressure seals were, well…I can’t figure out how the pump didn’t leak! Everything goes back together and I fire it up.
Chug, chug, sputter! Rattle, clack, rumble.
Cycling the unloader solves nothing, pressure pulsates, and rattling continues. I inspect all the potential culprits and finally check the
soap and wax inlet tubes (Maybe I didn’t fully push them into the push-to-connect fitting?) TaDa! The fitting is loose, leaking air into the pump’s inlet. The replacement fitting solved the problem!
So, somebody please tell me that I didn’t needlessly rebuild two of my pumps in one afternoon. I’m pretty sure that I damaged that
soap/wax fitting while it was on the bench.(?)
Oh…And, I made sure I wrote “BAD” on that “New Looking” regulator before I put it back on the shelf.