LS1 doesn't always start on first try, second try works.

Need to pick someone's brain. Since the build I've been having an issue with starting car after it's been warmed up. Cold start has been flawless every time. Once it's been warmed up it has done it anywhere from 140*-215* ECT so there isn't really any consistency with temp except that it's not a cold start. It also doesn't do it every time either but more often than not.
Turn key on (wait for fuel pump prime), try starting car and it will just spin over. Let off the key and try a second time it will start immediately.

I have checked fuel pressure and it's good with no bleed down. Trying to let pump prime, key off, then prime again does not change anything. I have tried FA Mult Stage 1 +/-, Prime Pulse Mass +/-, First Pulse Mass +/-, Cranking VE +/-, Startup Airflow +/-, Friction Airflow +/- and have had no change in this issue.

Crank pulse and Cam pulse is working even when it's acting up as you can see in the log attached "No Start" it acts up at the beginning then starts on second try. I have even tried a second cam sensor even though this one worked prior to the build.

Base Idle Airflow tables are dialed in within the available ambient temps in my region at the moment (I'll fine tune that for the colder temps when we get colder this winter). Primary VE is pretty good, ST and LT fuel trims are +/- 3. Still in break-in period so I haven't been able to do any hard pulls but the car runs pretty good.

Specs are:
2002 Z28 5.7/A4
LS1 5.7 Block
Summit Pro LS forged 3.66 crank
Summit Pro LS forged 6.125 rods
Summit Pro LS forged 3cc dome 3.898" Pistons
TSP 228r 228/228 .600/.600 112lsa
LS7 lifters
243 heads
LS6 Intake with factory injectors
TSP 1 7/8" LT with TSP catless Y-pipe
Circle D 3200 Stall

Attachment 115210Attachment 115211

Cam sensor won't cause that, if I'm understanding that it just cranks like normal but doesn't pop and bang and then eventually start and run. The cam sensor only distinguishes #1 TDC compression from #1 TDC exhaust, since those two are identical at the crank position sensor. If the CMP is MIA the PCM will try one TDC and if it doesn't run like that it will switch to the other TDC. If it guesses right the first time it will start and run with no apparent symptoms.

Does it have spark when it does the crank no start? Does it fire off on the first attempt if you prime it with a toot of brake cleaner?

If I hold the key down long enough (5 seconds or so) it will get a pop but still won't start until releasing the key and trying the second time.
I have not put a spark tester inline to see if it's getting spark when it's acting up nor have I tried any spraying of fluids. I can give that a shot tomorrow.

First thing I would try is hold the IAC open more while the car is hot. I use 21g/sec iirc while the IAT is hot. Also make sure park position is up there so the IAC is moving from very open position when you first turn the key.

This will ensure you are getting plenty of air during cranking.

From there just add fuel till it goes. Leave cranking FA Multiplier alone and play with the first pulse mass. Leave second pulse mass at nothing until you nail first pulse mass perfectly. On my car there was a very narrow range where it wanted to go. The number 0.056 to 0.058g? is stuck in my head. But its been months since I looked at my tune file.

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Originally Posted by projectghost

If I hold the key down long enough (5 seconds or so) it will get a pop but still won't start until releasing the key and trying the second time.
I have not put a spark tester inline to see if it's getting spark when it's acting up nor have I tried any spraying of fluids. I can give that a shot tomorrow.

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Hey! I know this is old! But I am having this exact same issue. Wondering if you ever fixed it? Thanks!

Ended up being a bad cam sensor. Cam sensor was replaced at time of build with brand new AC Delco sensor too. Ended up having sensor warrantied and it?s been great since then.

Quote:

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Originally Posted by projectghost

Ended up being a bad cam sensor. Cam sensor was replaced at time of build with brand new AC Delco sensor too. Ended up having sensor warrantied and it?s been great since then.

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was it throwing the code?

No codes. The cam sensor is a 50/50 chance it will be on #1 TDC. On the times it was not on #1 TDC it would not start until the computer saw CMP/CKP sync to determine which TDC it was. Was just a defective cam sensor sending wrong signal.