Not new to the site, but it has been a while. I have read through some related threads as well.

I have a well built and well engineered set up that I have had literally zero problems with since the last build.

6.0 L LQ9 Iron Block 402, boost prepped, blah blah blah, with D1SC speed density tuned at 13.5 psi. I can literally daily drive the car with pump gas and 675 RWHP/635 RWTQ. Low crompression ratio of 8.78:1. Behind an M6 and drivetrain is solid.

Last fall, before winter here, I started having intermitent hard starting problems. They eventually got worse and then the vehicle would not start at all. At first I thought it would be a fueling problem. Twin in tank pumps and boost indexed pressure regulator checked out fine, plenty of pressure. Found it to not be spraying fuel. Immediate thought is camshaft position sensor. Without taking intake off, was able to check and see that it is seated properly and bracket bolt holding it in has not backed out. Mechanic attempted a camshaft position sensor relearn. Went through the entire process but it did not confirm that it had been relearned and the problem continues. Checked with the tuners and they would not have deleted the relearn app for any reason.

Also, it appeares that the vehicle being cold, makes the problem worse. Connecting a battery charger at high level will allow the car to start. It runs perfectly after starting. This build was brand spanking new 10,000 mi ago and is just really beaking in. Have given thought to the fact that there is probably now some play in the timing chain, etc. and the sensor may be reading just on the edge of the allowable variances, thus causing the intermittent problem.

Just looking for thoughts or similar problems, corrections. It is not throwing any camshaft sensor codes as well. Next logical step will be pull the intake and check the sensor and integrity of the wiring harness, but was hoping to avoid that. Thanks for any inputs.

 

Bump.

 

Any of you experienced LS1ers any ideas, thoughts?

 

I neglected to include the fact that I am having a clutch replaced in the car. This apparently becomes a factor as the difficulties with the current clutch have caused some end play in the crankshaft, likely through the thrust bearing wear. The crankshaft appears to be moving about twenty thousandths. Have also learned that the intermittent starting problems can be overcome by turning the ignition to crank and then pumping the clutch repeatedly. It starts more frequently and quicker in this manner. Car is going in for a clutch in 2 weeks. Anyone seen anything similar?

 

weird... so is the trans in neutral when you try to start? have you tried swapping batteries? Have you checked all the grounds on the engine block?
What does it do when it doesnt start, just crank normally or crank slowly? If having the battery charger connected makes it start i would work my way from the battery back...