Needs to crank twice to start, even just a little "blip" and it goes

[kingtal0n]

Okay how about this. Today it only did it After I uploaded a tune, it does this, Sometimes.
Cranking -> forever. Nothing. I can crank 30 strokes or 3. it doesn't matter. Just one little blip.

Stop cranking.

Re-crank: starts on 4th compression stroke.

I haven't had it cranking -> forever until I upload a new tune. I guess I can live with that.

Is there some kind of wire that is active only when engine cranking? SR20 have that. If you don't put 12v to that wire when cranking it does the same or similar thing... sometimes

Update: I am going to try a momentary switch on the crank trigger that I can manually trigger before actually cranking.

[kingtal0n]

I get it to fire every single time now. Pretty sure what finally did it was the prime pulses. I kept increasing master prime, prime1 and prime 2 until it just starts immediately on the second or third stroke. I think its even a bit too much fuel now because one time my hand slipped off the key and it tried to start from just 1 stroke, starter is also dying so it turned really slow, sputtered a couple then stopped. Then re-cranking it was flooded, had to clear flood. So I think now what I want to do is reduce cranking table post-prime until it never floods.

Loving all these settings. should update my other threads to I've learned quite a bit

update1:
I returned the "FA cranking table" (what does FA stand for?) back to stock,
and pulled a bit of fuel out of everything and it still starts pretty good with just .1g in master prime (the key-on prime) and I think .1 or .2 in the first fuel pulse mass table also.

What I like to do is let it go 2-3 compression strokes (.2-.4 seconds of cranking) and let go of the key, it just sort of lags for a moment like its not going to start, then rumbles to life nicely.

[oldmanz]

I get it to fire every single time now. Pretty sure what finally did it was the prime pulses. I kept increasing master prime, prime1 and prime 2 until it just starts immediately on the second or third stroke. I think its even a bit too much fuel now because one time my hand slipped off the key and it tried to start from just 1 stroke, starter is also dying so it turned really slow, sputtered a couple then stopped. Then re-cranking it was flooded, had to clear flood. So I think now what I want to do is reduce cranking table post-prime until it never floods.

Loving all these settings. should update my other threads to I've learned quite a bit

update1:
I returned the "FA cranking table" (what does FA stand for?) back to stock,
and pulled a bit of fuel out of everything and it still starts pretty good with just .1g in master prime (the key-on prime) and I think .1 or .2 in the first fuel pulse mass table also.

What I like to do is let it go 2-3 compression strokes (.2-.4 seconds of cranking) and let go of the key, it just sort of lags for a moment like its not going to start, then rumbles to life nicely.

I know it's old, but I am having this same issue. I will try this, and I just wanted to say: Thanks for updating!!

[bk2life]

I get it to fire every single time now. .

ive got a customers 2003 tahoe that does this.
will not start on 1st try. Owner's mad becuase he cant use his 'remote start'
2nd time cranking and will fire right up.
I'll look for 'master prime'..

[5_Speeds_in_OKC]

My 2003 2500HD 6.0 exhibits this same behavior. On the first crank cycle it won't start and will backfire if you keep cranking it. On the second crank it immediately starts. I have monitored fuel pressures -- they're right where they're supposed to be. No codes point to a potential culprit.

In the research I have done, someone, somewhere commented that these old PCM's have underperforming capacitors (as they age). In a nutshell, during the first crank cycle, a particular capacitor doesn't have enough residual energy stored in it, so isn't doing what it's supposed to do, but it gets a charge during that first crank cycle, however brief it may be. On the second crank cycle, that capacitor has some 'juice' in it so it can properly energize whatever circuit it is tied to. The only remedy for having old capacitors is to get the PCM rebuilt.

I just live with it...

[kingtal0n]

backfire on first crank is a bad cam sensor

[5_Speeds_in_OKC]

Interesting thought on the Cam Sensor; however, if the Cam Sensor were faulty, wouldn't we expect a Code to be triggered?

Could it simply be time for a Crank Relearn?

[Ben Charles]

Interesting thought on the Cam Sensor; however, if the Cam Sensor were faulty, wouldn't we expect a Code to be triggered?

Could it simply be time for a Crank Relearn?

Not every time will it throw a code, part store sensors will sometimes not throw a code and still be at fault. Get an ACdelco sensor and you’re problem will go away

[kingtal0n]

Make sure you have the correct cam sensor voltage and pinout
24xvs58x.png


And correct wiring orientation
camwiring.png

guessing you are gen3 but just in case I show both