[MT-2500]

Originally Posted by mrharris32

I've just recently replaced the motor in an 02 burb. The old motor had 270k miles and had some fairly severe bearing damage. I picked up a new motor (complete) with 71k miles, I am 100% positive the motor ran fine before I purchased it from LKQ (huge salvage centers nationwide).

After about 35 hours of labor I've got the old motor out, the new in and everything connected...every sensor, every wire, fuel, etc. I've been wrenching for over 12 years so this isn't my first rodeo. After installing the last of the parts (fan shroud, heater core hoses, connecting the battery) I hopped in and turned the key. Turns over fine, oil pressure jumped right up, motor studdered a few times. I hopped out and purged the air from the fuel system (using the purge valve on the incoming fuel line top of the intake), standard protocol on any late model 5.3 swap. Turn the key again assuming she'll fire right up, turns over and hits just a bit but will not start.

After several hours of troubleshooting I'm still stuck. I plugged in the scanner and received NO codes whatsoever. The only variable in the electrical system was the camshaft position sensor, the pigtail was destroyed when the old motor was removed...I wired in a new pigtail using the wiring diagram found in a Chilton's for 2000-2006 Chevy 1500/Suburban/Tahoe. I pulled the connector from the back of the intake (not easy when everything is installed!!) and cranked the motor, immediately got a code the the CPS was not functional. Basically I was trying to rule out whether or not the wiring could be off....it appears to be fine however.

With that said the only other issue with the motor is one bolt missing on the driver side exhaust manifold, you can hear it squeaking out a bit but nothing serious and certainly nothing that should cause it to not start? From my experience I am leaning strongly towards the engine being seriously out of time...it's shooting fuel/firing spark at the wrong time. There is no way to my knowledge to adjust this...

I'm at a loss, 12 years and tons of swaps, never had this problem. Could there still be air in the injector rails? Did I miss a crucial step required before turning over a new motor in a 02 Burb? I'm looking for any input and will give as much info as needed, I need to get this vehicle going ASAP.

Thank you in advance for any assistance!

What engine?
What is the fuel pressure?