Hard cold-start problem. Helps?
 

So ever since I replaced my engine back in July, I've been having an issue on cold-starting. It's only on VERY cold starts like overnight and after the car has been sitting while I'm at work. I have Hydra 2.17 and I know it cranks the engine more than normal to check timing before giving fuel/spark. But this issue is much different.

On the first attempt to cold start, the engine turns over normally and then starts to fire, but it just sputters badly and stalls out. *Sometimes* it will sputter and idle at like 200rpm and then cut off. Upon the next attempt to crank everything will work normally. I've tried feathering the gas while turning it over to see if it changes. It seems to make some difference and will sometimes sputter -> low shaky idle for a couple seconds -> "find" itself and idle normally.

BUT

Lately with the temperature being much colder, it's taking 2-4 attempts to fire up. Once it runs, I can turn it off and it'll crank right back up normally.
I don't think it's fuel enrichment/cold start settings or excessive fuel. I don't get any excessive fuel smell from the exhaust (like I do when it sometimes stalls and takes a moment to crank up..but that's another issue for another day).

The only thing I can think of is that the crank sensor is just a fart too far away from the crank pulley and signal isn't great when cold starting...like the metal has contracted enough to cause a weak signal pickup. When we swapped the crank sensor over, we used a feeler gauge that the FSM calls for...but it may have moved when tightening down. Anyone ever had a similar issue?

change the fuel enrichment, bitch.

Would the enrichment really be different between starts that are 2 seconds apart Sir Homobottomofthebarstool Sr.?

I imagine that a couple rounds of flame through the clyinders warms-up things dramatically. I recently fixed this in my car where adding .2ms cranking fuel in one cell made it go from 3-5 cranking attempts to the first time, every time. My after start enrichment still needs a touch more work, but now the car starts the first time rather than a few crank attempts.

I shall look into it then. I really question because the entire life of the previous engine, there was no starting issues at all and it only started when I replaced the engine. I know the fresh engine has a bit more compression due to it's newness...but enough to make a significant difference in starting? The previous engine was boosted very early in it's life...so I wouldn't imagine that the cold-start enrichment would be much different on a fresh engine. At least that's my idea behind it.

Adding cranking pulse width would be the first thing to try. You really only get one crack at that per day, on the very first cold crank in the morning, because once you burn fuel, even if it's just enough to make it stumble, that heat will affect the next crank attempt as hustler has pointed out.

Does the Hydra have a field where you specify cranking rpms? In other words, the rpm below which it will still inject cranking pulse widths before switching over to the running fuel table? In my MS I adjusted cranking rpm up to 400 (was originally 250 or 300 IIRC) and it seemed to help keep it from doing the 250 rpm stumbling and dying routine. If you get to the point where it seems to crank and catch "pretty well" (as opposed to just stumbling) and then dies right away, you need to bump up the after-start enrichment % at that temperature. This is MS terminology as I'm not familiar with Hydra but the concepts should work more or less the same.