Not exactly sure on the engine model but it was one of the last cat engines. Anyway I’m having issues with the air building. Primary builds at a okay time but still longer than 3 mins it’s at like 60 at 8mins then finally secondary starts moving and I believe truck gets full air around 15mins revving at 1200!
I changed the unloaders. Fairly new compressor by looks of it! And an air dryer filter. But if it takes forever to build in secondary what could be the issues?