Hi folks,
I've posted an extensive thread at S10Forum.com and LS1Tech.com about this ordeal and I recieved some great suggestions but none have turned out to solve this.
Some background.. I have a 2000 S-10 pickup that had a 4.3 and 4L60E. I replaced that with a 5.3 Vortec and 4L60E from a 2000 Sierra. The only internal mods are a 2002 LS6 cam and springs. The wiring harness is from Current Performance Wiring and plugs into the stock power distribution box in the truck.
What's happening is on first crank, I get a few revs of firing/ignition and then nothing. Continuous cranking yields nothing, it just cranks with no activity. Every time i let off the key and re-crank, it sputters again for a few revs. I have HP tuners and have logged some of the important bits. After a few revs, the injector duty cycle drops to 0% and continues there until i let off the key.
Here is a screenshot of 4 distinct crank attempts. http://i.imgur.com/ZSqIMeM.png
Here's is a video of what it sounds like.
http://www.youtube.com/watch?v=_CqqvpJfqHE
Sometimes it'll fire for a few more revs but never gets to 'running' status. It runs longer (2-3 seconds or so) on a squirt of starting fluid but I don't have arms long enough to spray and crank at the same time.
The fuel pump is stock, and I think the check valve is dying. Prime fuel pressure is 62, and bounces between 55 and 65 during crank. It drops off quickly after the pump shuts off. I have a new pump en route. A GM tech suggested I try pinching the return line a bit to maintain some pressure, and I did, and no difference.
I have checked the CKP and cam position wiring and sensors and they are good, and brand new. I have good data from the coolant temp sensor which is new, IAT, MAP, and MAF which are reused. I have disabled VATS through HP Tuners. The rest of the tune is stock 2000 Sierra. I really feel like VATS is not actually disabled.
I have written a VATS-disabled tune, and reread that tune back to verify it's listed as disabled, and it says it is. Column lock is also set to 'none'. The injectors fire 3 times or so for each crank attempt and then go dark.
I have a new PCM en route as well, thinking it might be something there. I have ground straps running everywhere to try to rule that out.
Any leads would be most helpful. I can't spend any more time on it this week but Friday I plan on installing the new fuel pump and trying the new ECM.