Hi everyone,

hope it is ok, that this is my first post.

Backstory:
the LS3 is swapped in an older BMW (e28). It is an LS3 with a little cam and springs, cable driven throttle body, headers and exhaust fitted to the car, otherwise stock.
Last year I got the engine running on a little stand with the Holley Harness, with no bigger issues (Holley Wizard was way too rich, but otherwise everything was fine).

Present:
Now it is in the car and wouldn't start with the same tune, no changes to the engine harness etc. . Changed a bunch of stuff around in the tune, didn't have any influence. Backfires into the manifold and pops out of the exhaust and wouldn't start at all. Checked the diags 6 and 7 for cam- und crank-sensor 0, it shows RPM of around 150-180 on the starter. It has spark and it has fuel. Checked the wiring to the coils and injectors multiple times. Changed batteries two times, checked ground etc. .
After several hours, we were sure it had to be an ignition problem. We marked the damper and the block with a little line for cyl1 TDC and used a flashlight and it wasn't even close. We turned the engine around 180degrees and marked the damper again with 2 dots. And with 0° cranking spark in the Holley it was spot on the 2 dots. Like in the old times, when you put in the distibutor in the wrong direction.

At that moment I could feel a headache coming...

I read a post form a ford guy, who had to change firing order for his 5.0 to run.
After some argueing between us (4 guys with beer...), I changed the firing order in the Holley Software from 1-8-7-2-6-5-4-3 to 7-2-6-5-4-3-1-8 (180 degrees around).
And guess what: it fired right up, as if nothing has ever happened and did it several times...

Please remember: the engine ran on the stand without issues, with the same harness and Terminator X and tune. Now I had to change the firing order, to make it start.
On one hand I am happy and a bit proud that I got it to start, on the other hand I can't wrap my head around what is going on...

So please, can anyone explain this "miracle" to me?

Thanks everybody for reading and sorry for my bad english. (German trying his best, but being out of school for more than 25 years)

 

Did the coil harness get plugged into the opposite sides?

I have no idea, if that had happened, if changing the firing order would fix it.

 

Check your cam and crank sensors. I think you can do a system?? Datalog while cranking and they should tell you if those sensors are working or not

 

Thank you for your answers.

Coil harness is correct, checked it again. Sensors are okay, as I wrote above (Diag 6 and 7 don't count up) so no errors there.

After several more hours of getting it to start but not stay in idle, we finally got it to idle.

It runs with the the firing order 7-2-6-5-4-3-1-8, I am still amazed how that is even possible.