I have a 2009 Suburban that cranks for days but won't start, it has spark and fuel pressure no DTC's set or historical codes. I did a compression test and only have compression on one cylinder of 55. Don't know what the heck is going on any clues, I don't think it detonated and put a hole in every piston or blew every portion of the head gaskets. Cylinder with 55 is 2nd one back from the grill on the driver side and yes I did a wet test and it went up to like 57 all others remained unchanged.

 

Welcome to the forum.

Timing chain broken? Also throttle blade should be wide open when doing compression checks.