Question on Cold Starting

[Ric Rainbolt]

I'm trying to tune a custom EFI system that I've developed and I'm having
trouble with the cold start.  By cold I mean room temp, which in my garage
lately has been about 70-80 F.   I've tried many settings from moderately
rich to "pig" rich and nothing at all happens until I squirt some Carb
cleaner into the manifold.  Once I do that, the engine will hit and then may
start (or may not).  One or two shots of Carb cleaner more and it starts and
runs (at which point my warm up cycle takes over and seems to work OK).

More info:
  8 cylinders with port injection
  Injectors well matched to engine output
  No cold start injector
  250 RPM cranking speed nominal
  Good spark, new plugs
  Hot re-starts work OK

Does anyone have any info on good "start" algorithms?  One that I have not
tried yet is a rapidly decaying very rich to a little rich scenario.  Say,
2x to 3x the normal amount of fuel for the first few revs and then back off
to 125% over a 20 rev range.

What do "factory" systems do?

Ric Rainbolt
ricrain at airmail.net