Installed new Ink Pumps - Roland SC 540 ... 2/3 Failed from the start ... reason?

[96XP]

It's been a few months, and meant to post my question sooner: that if anyone else had ever experienced this same issue, and what reason (diagnostic) there could be for the new pumps to be defective.

'Generic Roland XJ-540 / XC-540 / VP-540 Solvent Resistant Ink Pump - 6700319010'​

~​

A few months back, I decided to order 3 new ink pumps, just to be prudent.
After first install, I had noticed they were very noisy, a shriek I'd never experienced before when they were actuated.

Two of the three that were installed didn't do the job - and my caps were: floating ink/not draining, and that was the initial cue.
That said, some heads got temporarily clogged as a result.

I then removed them, opened for inspection, then reinstalled, to no avail. Ended up putting the old pumps back in as they were still functioning.

Any idea what part is faulty? Perhaps the 'U' shaped tube within the pump? Should I swap the tube for the old?

Thanks for reading.

 

[netsol]

WHERE DID YOU PURCHASE THEM?
perhaps you got chinese look alike pumps?

 

[96XP]

WHERE DID YOU PURCHASE THEM?
perhaps you got chinese look alike pumps?

sign-in-global - I see they are now advertising "Improved Roland Solvent Resistant Ink Pump". They must have skipped the quality control phase on my order. Neither do they have OEM. Still curious what failed in the unit. And they are fascinatingly simple in design.