Lets play "Diagnose My Motor!!"

[LA_phantom_240]

Long story short, me and a friend of mine are swapping a 95 KA into my 91 240sx. Everything went pretty well until time came for her to fire up. she runs on cylinders 1, 2, and 3, but 4 is dead. Compression was like 145 (low, but still able to run) and she is getting spark. We thought the injector may be bad, so we swapped it out with one of the s14 injectors to no avail. Im going back tomorrow to HOPEFULLY finish the job... Any suggestions?

[the head]

is the injector firing? if not you may have a bad injector driver in your ECU

[LA_phantom_240]

Well i still have a spare ECU in the car. Im gonna switch out the #4 injector with eh #3 injector, and if she fires on 3 ill know its electrical somehow. At that point ill try to swap my ECU and see where we get from there...