Couldn't find any information on this doing a search. Very little advance is shown on the arap bin. I've been trying to clean up my cold start and was curious how changing the cranking spark curve affects the starting. I've played with the starting fuel up and down and it never gets it starting better. Hard to believe they set the cranking spark curve to 0 deg across the board on the arap bin.

 

You probably know this already, but typically until about 400 RPM you're firing off the ignition module, not the ECM, so the advance is whatever the distributor is physically set at for base timing.

You might try varying the base timing to see if it makes a difference. As long as you change the base timing value in the bin to match whatever the distributor is physically set at, your total spark advance above the EST threshold will remain the same.

If you find the engine wants more advance sooner, you could try lowering the RPM threshold that the ECM takes over control from the module. I've done that for $8D, not sure exactly where that value is located in $6E though.

HTH,

 

Do you think 10 deg base timing is too much for starting?

 

GM specified 10° on some cars. 6° seems to be a lot more common. 10° worked OK on my ZZ4, although I eventually dropped it back somewhat.

Just a thought, but is the fuel pump relay working properly? The way most GM cars are wired, if the fuel pump relay goes **** up, you'd have to crank the engine until you had about 4-5 psi of oil pressure, before you'd get voltage to the fuel pump, via the oil pressure switch.

 

That's a good idea, didn't think of it. You know how the obvious is always over looked once you get into it. But I checked it out and the fuel pump kicks on right when I put it to the run position.

My real delimea is that if I open the throttle blades any more then when you start it up the car will rev past 1800 on a cold start which I think is getting pretty high. Now if I close them up more then the car doesn't like to start. I've added fuel to the crank vs. coolant table and that never really made any positive changes.

 

There's also a crank pulse vs ref pulse table that is usually zeroed out for the first two revolutions (8 ref pulses) on the stock calibrations. I just last night tried moving that so the first fuel pulses inject on the third reference pulse, and that makes a big difference on crank time.
The IAC position at cranking can also affect it.
If I were you, I'd compare what you're using vs AUJM, or ARAP.

 

While things vary by mask.
You basically have, cranking fuel.
Then PW per ref pulses.

Battery voltage correction for PW.

Then you Choke fuel, and decay rate, vs temp table.
Maybe a closed throttle closed AFR.
None C/L AFR

Then your warm park IAC, and max IAC.

For the V8 I use an initial of 8d. Less then that and on a cold morning the engine kinda just windmills since there's not enough timing, and more then that on a real hot day can cause slow cranking.

 

so technically there is no fuel injected at all until 8 reference pulses? What exactly is a reference pulse?

 

It's the signal the module generates based on the distributor/crank sensor signal.
In effect it means the engine has to turn over twice (8 pulses), before the ecm starts to supply fuel. Think of it as a prelube system, the 2 cranks gives the engine a lil time to get the oil moving. And to be spinning fast enough. Cutting them back can lead to spitting back, and nasty behavior in cold weather. BTW, backfires when cranking can be real hard on the MAP/MAF, and vac lines. I've had one blow the screen out of a LS1 MAF.

 

Set them so that at hot/normal idle you have 20 or less counts.
Then work at what get you a good start with the IAC park, and max counts.

Then once you get it so that kicks and intially fires for a few seconds work on the choke AFR. Then on the decay rate for the choke AFR.