What was found
SEA FLIGHT NR 2438: SELECTING FLIGHT TAXI TO FLIGHT, INBD LIGHTS DO NOT ILLUMINATE OR EXTEND. FOLLOWED CHECKLIST, COULD NOT CLEAR FAULT. ROLL INBD SPOILERS ON RIGHT SIDE DOES NOT EXTEND FOR A SECOND, THEN RETRACTS LEAVING ONLY OUTBD SPOILERS EXTENDED. AIRCRAFT RETURNED TO BLOCK. MAINTENANCE REMOVED AND REPLACED BOTH OF THE LIFT DUMP VALVES FOR THE INBOARD ROLL SPOILERS IAW Q400 AMM 27-62-01, PGS 401-407. PERFORMED OPS CHECK OF GROUND SPOILER SYSTEM IAW TASK 27-62-00-710-801. OPS CHECKS GOOD. LEAK CHECK GOOD. AIRCRAFT RETURNED TO SERVICE.