continuous check print engine test printing

[Remery18]

hp 4050N prints one job then runs check print engine test runs until paper used up.

replaced  feed roller and clutch in tray 2

just keeps printing lines until paper is used up

[NC77]

The engine test button is on the Engine Control/Power supply board on the bottom of the printer.  You perform an engine test by inserting a non-metallic object in the hole below the fan exhaust vent on the left side of printer.  Find a canned air straw, power up printer, and insert straw into engine test access.  See if it will print one test sheet.  Spray some air to remove any debris.  Continuous engine test may mean a defective engine board.  You have to separate printer from the feeder to gain access to it.  Even then, you will probably break more parts than you fix.  Good luck.