Weird Cranking Saprk Issue

[onegonewild]

I logged EST PIDs and could only acquire data when the engine was running. The only PIDs that affected the timing when idling was the following:
EST - Base Spark
EST - Idle Spark
EST - Run Spark

Is there any way to log these while cranking? I can never obtain data for EST PIDs during the startup procedure.

Any ideas what i could log that would show the timing being added during startup?
This is a stock Vortec distributor with MSD wires. Any chance the distributor could be the issue? I have no misfires when the engine is running.

[onegonewild]

Little more troubleshooting here, the engine startup routine is nearly the same with the Camshaft position sensor unhooked. It still has way too much advance in timing (like before) with the sensor unhooked. I did the basic testing out of the CMP sensor, 12.7 V in and 10.8 V signal to the PCM. This does drop to 0 V and back up to 10.8 V when the engine it turning.

Ideas?

[joecar]

Where is the sensor location for the CKP and CMP sensors...?

~ posted by phone ~

[onegonewild]

CMP is in the distributor. CKP is in the front timing cover

[onegonewild]

RESOLVED:
NEVER TRUST reman distributors from local parts houses. This distributor has less than 1000 miles on it and is shot.
Luckily i had a donor vehicle to trade parts on and compare. Pulled the distributor out and noticed a good 1/2" or more vertical slop in the shaft. I swapped it out for one that had less than 1/16" vertical play. SUCCESS!! Starts perfectly!

For anyone having an issue with Vortec engines adding a crap ton of advance timing on starting, this is most likely your issue. All the slop allows the distributor to climb of the helical gears on the cam and change the timing. This most likely was attributed to the reluctor window not passing through the Camshaft Position sensor correctly.

The PCM definitely references the CPS while cranking for proper timing. This acts like an old pickup coil.

[joecar]

Good job on finding the cause.

Climbing the helical drive gear accounts for the extra 60 or so degrees of timing.

~ posted by phone ~

[onegonewild]

Distributor spec'd out perfectly when I originally installed it. Even the Camshaft position sensor reported good with proper values during hand turning.

Totally different scenario when cranking as the rotor is pushed up.