THX-1138 wrote:...How can some one check the injectors {"ejectors", might be more descriptive} while its running?
That tactic
would be a bit tricky -- probably requiring the use of a very large, glass-topped coffee-table! In my post above, I was suggesting the un-powered flow-check, and assuming two people would be needed. One to look, one to pressurize.
...Also what would stop flow?
We have two cases, as far as I can tell from the posts. We have a) No-Flow cases, right out of the box, and b) Induced no-flow, by something the owner caused (and cleared). Type (b) cases can be cleared (should be able to be cleared) by the owner, by flushing the CT, and back-washing its outlet fitting and pre-filter.
Type (a) is mysterious because, both jet-paths are blocked, and it IS a fault that should have been detected at the factory. We will never be told whether the factory does a wet-pump check-out. My guess is they would do it early in the assembly sequence, like before fitting/sealing the Controller's cover. At that stage, they could feed the pump and conduits with water and run the pump-motor via a test-connection direct to the motor-cable. When finished, the wet-system could be air-purged to remove the test-liquid.
Whether they do such a trial, or not, I must assume they are careful to not contaminate the liquid pathway, because they know some particle stuck under a valve will disable the pumping. Note that this type of "blockage" impairs pumping, but when the pressurized clearing tactic is applied, water, or air should flow out both jets -- perhaps more from one than the other.
I have the impression, from descriptions given on this board, that there is no flow -- until something breaks loose, to free up the flow. That action fairly well says the blockage is probably due to valve-diaphragms being temporarily stuck to their valve-seats. That suggestion depends on the common feed-pipe being free of obstruction; and I think it is fair to claim that conduit is not contributing to the problem, since relatively large size debris/globs would have to be present to block that line, and if there were such debris, no one would be able to blow it all the way throught the pump, and OUT the jet orifices (they have only one-mm size holes).
So, what are the prospects for valve-diaphragm-material to adhere to the valve-seat-material? I don't know. Based on the 'feel' of it, I would guess its a polyurethane compound. That material exhibits slight self-adhesion to clean, smooth surfaces. I can say that adhesion need not be very great, based on testing Roger did. He checked "lift" of his pump -- to demo whether the pump had any self-priming capability. It does not. The pump must be gravity fed -- as the Tank normally provides. That tends to say that the pump's intake action cannot apply enough force to an inlet valve to de-stick it.
OTOH, IF the outlet-valve is stuck, but not an inlet-valve, that side of the pump should be able to intake a chamber full of liquid, and then as the compression stroke occurs, the inlet-valve will seal and all the force of trying to compress liquid will be applied to lift the outlet-valve and cause pressure relieving flow. So cases having ONLY stuck outlet-valves might be self-healing. These case could be occurring, and we don't know it, because there is no need to complain!
Regarding the 'sticking', there is no appreciable force on the diaphragms, to force them against their seats -- its only the radial tension in the disc-shaped valve-diaphragm (I hope everyone is following along by looking at "Scooba Technical"'s Pump-Section) that impresses (a very small) force on the seat.
At this time, I can only guess that sticking is due to dry-shipping. iRbt will never tell us. Some new owner, who is experiencing this blockage, and who has the guts and mechanical expertise to follow the path in Scooba Technical, will have to dismantle his new Scooba and carefully remove the flexible-casting from the pump-plates, to see if the material is sticking to anything, or if some other cause becomes apparent.