I really need some ideas on my LT1 swap, pretty stumped.

i rebuilt the LT1 after i bought the car, dropped it in, and with the previous owners modified lt1 harness it ran for about 30 minutes one night, next day wouldn't start, his harness was really badly done, so i bought another stock harness and wired it up with a vats bypass chip and got everything hooked up to the thirgen, but the car wont start.

the car will fire up and run at 2000rpm for about 3 seconds then burble dead every time.

its getting good fuel pressure at the rails, and the injectors are firing, i checked them with a noid light. it seemed to have spark aswell, but it wont run.
i put the lt1 pcm in limp home mode by jumping the serial data wires and it made no difference.
im starting to think it may be the optispark, it was fine before but the car has been sitting for a year, i really dont know much about them though.

but any ideas what it could be would help a ton..really want to get this thing running.

 

Vats is a fuel cut so try a can of ether to keep it running a few seconds more to rule out vats

 

i've had the car run for more than the 3 seconds before, i once throttled it back to life but it died a few more seconds later, also i the noid lights i used showed that the injectors were getting signals all the way until the engine completely died. so i dont think its Vats.

 

check the opti harness. they're famous for going bad.

when it dies, check for spark right away. might tell ya something?

Pocket has a good idea.

might sound stupid, but check for a plugged up fuel filter.

 

has the PCM been altered to bypass the VATS? .. If so, check the obvious before you suspect the Opti..
IAT sensor should be plugged in. It's on the rubber elbow.
What year is the motor and what year is the harness? and what year is the PCM?
a coil module can do that too.
To my knowledge a VATS chip will bypass your chip in the key but you still have to deal with the PCM. If you don't bypass the VATS detection in it then it won't run. It's not as simple as jumping a wire to another wire. You have to produce a square wave .. IE program the VATS out of the PCM as that's easier

 

Pull a coil wire off and check for spark from the opti. Sometimes the water pump likes to leak from the weep hole and will fry the optispark..That's exactly why I'm converting to carb and back mount distributor.i won't have that problem anymore AND she's gonna pull a little better making a hit.Still having trouble with mine too.Mine won't start at all she backfires like the timing chain jumped a tooth or something.