I've replaced the engine on the '02 Montero (3.5L). The lifters on the right bank stay pumped, and there's no compression. The left bank behaves, and I get good compression. I've replaced them with brand new Mitsubishi parts - still same deal. No OBD2 error codes. What could cause this?

 

sounds like you have bent valves.

 

I was kinda thinking that initially too. But I've checked the valves - they're good.

 

check your timing belt marks