What happens to the priming pulse when cranking immediately?

[subwoofer]

I am trying to get the engine to start as fast as an OEM system. I am getting close, but not quite there yet. I've ended up actually having a rather long priming pulse at low CLTs (again), but suddenly it struck me:

What happens to the priming pulse when you go from off to cranking as fast as the key can turn, not waiting for the fuel pump on/off and priming pulse cycle? Is it simply skipped, is it run just after the first tooth is detected, what happens?

[muythaibxr]

I'll have to check the code to be sure, but I believe we run it as part of our init routine... which means it should happen regardless.

Ken

[subwoofer]

But ordinarily that init routine waits for the pump, does that happen when cranking happens straight away too? In that case, that would explain why I can't seem to be able to get it to start in less than six compressions.

[jsmcortina]

The init routine does not wait for the pump.

James

[subwoofer]

Is my memory completely out the window? I seem to remember a setting controlling an initial pump run after power on to build pressure, I can't seem to find it. Not that it really matters, the regulator takes days before it leaks down.

So the prime pulse delay is skipped when RPM is detected before the delay expires, and does not delay any other functionality? What happens when prime pulse and ordinary fuel events overlap?

[sd1nl]

The priming could take place in the time the engine is in the "skip pulses" delay. If this is long enough there is plenty of time.