LS1 doesn't always start on first try, second try works.
Thread Starter
Teching In
Joined: Apr 2012
Posts: 4
Likes: 0
From: Denton, TX
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
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
Check the fuel pressure when you turn the key on and make sure the pressure stays up for atleast a few seconds. If it jumps to 60 and then falls back to 0 then the check valve is bad.
What you can do if you don't have a pressure gauge is - turn key on but don't start and wait for the prime to stop, turn it back off and then turn it on and crank it all in one motion. If it fires right up, its the check valve in the fuel pump not holding pressure after fuel pump prime.
What you can do if you don't have a pressure gauge is - turn key on but don't start and wait for the prime to stop, turn it back off and then turn it on and crank it all in one motion. If it fires right up, its the check valve in the fuel pump not holding pressure after fuel pump prime.
Thread Starter
Teching In
Joined: Apr 2012
Posts: 4
Likes: 0
From: Denton, TX
Thanks for the reply, already got the issue figured out in the tune.
as stated in my original post, fuel pressure was already checked way before making the post along with bleed down.
as stated in my original post, fuel pressure was already checked way before making the post along with bleed down.
Thread Starter
Teching In
Joined: Apr 2012
Posts: 4
Likes: 0
From: Denton, TX
Park position on the IAC was too low in the tune. It was having to travel too far at the start. Raised it up by 10% on the warm temps. Cold starts were fine but the cam needed a bit more air.
