Welcome to iRV2. and the Newmar family.
My 99 DSDP on F/L chassis has only one air suspension system dump solenoid , your Spartan chassis MAY have two .
Is your leveling system HWH ?
If HWH do you know the series number ? 310 ? 625 ? Auto leveling ?
Is this a new problem, or a problem on a new to you coach?
My HWH 310 series; manual leveling; the single dump solenoid is at the left front wheel and the rear suspension takes a long time to drop, because of the distance to the dump solenoid .