Brand new GMPP LS376/480 crate (LS3 with hot cam) hard to start when warm

[EVOVII_SWE]

Hi,

I have just swapped an LS7 for a brand new LS376/480 from GMPP in my AC Cobra before it was sold. I also bought the GMPP controller kit to get it to run. I re-used all the wiring and mechanical surrounding parts from the LS7.

After the swap, I noticed some problems to start the car when the engine was warm. Cold starts works perfectly and once it's running it also runs perfect. But if I stop the engine when fully up to running temp and then try to start it after a few minutes it needs several revs on the starter before it ignites and fires up, which it does in a slightly hesitant stumbling kind of way. Same thing here, once it do start up it runs perfectly.

I never had any issues like this with the LS7, it always started more or less immediately regardless of temperature.

At one point, I provoked the new engine and made several startups after each other, and roughly at every second one it started immediately and the other ones it needed a few more seconds on the starter.

The most embarrassing thing was when the new owner picked it up, it started at once and then he left but called me some 10 minutes later when he had stopped and shut down the engine to open his garage and then it wouldn't start at all. I went there and it runs fine on the starter but never fires. Then we left it sitting there for a couple of hours to cool down and tried again, and bam, it just starts immediately.

At this moment, I have not been able to connect my HP Tuners due to some computer issue but I'm hoping to have it resolved shortly. However, it did not throw any CEL or so and no error codes were present when using a stand alone OBD2 reader.

Any suggestions or ideas where to start with this?

[lukearmstrong1990]

Possibly lean on cranking when it’s warm or not enough start up airflow for the operating ECTs.

Try editing the cranking FA multiplyer table under fuel, general. Also try adding some start up airflow. Check to see that the startup flare control isn’t to aggressive that it’s hindering your startup.

To much or too little spark during cranking can also effect it. I find fActory values with 10 degrees above 80 degrees C ECT to work fine

[EVOVII_SWE]

Thanks, I'll need to sort out my laptop that for some reason will not recognize the USB connection, then I'll have a look.

[Area47]

not enough base airflow and startup airflow. Have had the same issue on all the of the ones I have done.

[EVOVII_SWE]

not enough base airflow and startup airflow. Have had the same issue on all the of the ones I have done.

Thanks, any concrete suggestions on how much of an increase to begin with?

[Area47]

try 10% as a start and go from there. You can drop the cranking ve to 90 and see if that helps. I do not have my laptop with me so I do not have a definitive answer.

[EVOVII_SWE]

Thanks, I'll look into that as soon as I have sorted out my laptop and have access to the car again.