My 97 pathfinder 3.3 2wd does not fully start.

I have replaced relay,gas filter,gas pump,whole distributor (checked rotor under dist.top to see if it turned when cranked to verify timing belt function, it turned in a slow to moderate speed)I have replaced and cleaned crankshaft position sensor(was dirty with leaked oil,not sure from where) I have attempted to start it with starting fluid(it cranks over but turns off immediately) I tested with a test light on the fuel injection cables it did not lit .Today we took it to get a computerized diagnostic and the only code it presented was po120. I was told to replace the TPS but, it doEs nOt seem to me that would cause a no start condition( when i asked i was not given an answer at shop i did comp.diagnostic today i was recommended a shop..i really want to learn to work on it myself for auto-sufficiency purposes ) . The pathfinder when it did start was weak and piston noisy when accelerated. check engine light was on sometimes. had low fuel economy less than it should. I bought this pathfinder a year ago it has now 253 k . I was told due to crash in front radiator was replaced but other than that the pathfinder had more force when we bought it. I appreciate any insight and help, Thanks! O and fuses seem fine I was under the impression damage should always be visible I will use test light today! Thanks!