The machine cannot perform the vacuum function. When the engineer repaired the customer machine and replaced a new solenoid valve, it was found to be useless.
The machine cannot perform the vacuum pumping function. When the engineer overhauled the customer's machine and replaced it with a new solenoid valve, he found that it did not work.
The machine can't perform the vacuumizing function, and the engineer found that it didn't work when overhauling the customer machine and replacing it with a new solenoid valve.