Couldnt find anything close to this problem in a search, so here we go!
I dont have any one vehicle to post a tune of but im looking to get some idea to help theorize what is taking place or better still the order of events needed for the engine to make a quick start up.
Here is what happens:
The complaint is the engine will not start on the first attempt, you hold the key and it just cranks and cranks and cranks. let off the key back to "ON" for a split second, crank it again, bam instant authoritative light off! Not EVERY time though does it need this proceedure however.
Commonality between the vehicles that do this: All are Gen IV conversions, PCM types are '99 plus, and the platforms truck, F-Body, and Vettes. All have had aftermarket stroker cranks and aftermarket cams and cam timing sets. Some are in the vehicle the PCM came from, some are swap vehicles. No Cranks sensor or cam sensor codes are pressent, the LS2 conversion kits did have the cam sensor wiring verified (they didnt start at all or for shit when wired wrong) and are using the the stock gen III crank sensors. These conversions are using the LS2 sensor and the half moon reluctor on the big cam gear. Case learns have been performed on the vehicles that would allow it to work, no change.
To me it allmost seems like there is no crank signal. Problem is that i cant tell for sure because the scanner disconnects from the PCM everytime you go to crank to start the engine. However the tach doesnt appear to "wiggle" at a couple hundred RPM like it does when a normal starting vehicle is cranking. The things start and run perfect after that second key hit though. Fuel pressure has been proven adequate (60 psi) at the rails too on all of these during crank FYI.
So my question is, how does the PCM sync the crank and cam signals to allow it find #1 or however it works to allow an imediate start? Seems that these aftermarket cranks with the supplied reluctor is suspect to me. Could it be off time ever so slightly? Or is there simply some settings in the PCM that should be manipulated to get rid of this event.
There are 4 vehicles i know with the same exact issues... different ages, different CI, different platforms... all one common fault though.
Ideas, thoughts, sugges