Trying to repair a 1986 Deville Electric Vacuum Booster Pump. Can anybody
please tell me the GM part # so I can try to find more info? Can't seem to
locate this part anywhere on the web.

My troubleshooting so far shows good exhaust air on the output port but no
vacuum on the input port. Took the vacuum chamber off the cylinder head and
eye-balled the pump while it was running. The electric motor, solenoid,
piston & cylinder, and cylinder rubber washer all seem to be in good
condition and work fine. The vacuum side check valve operates freely and
the pressure side check valve seems ok. Anybody have any suggestions for
what to check next.

TIA Scotty