Mario, if you have already increased the pump start voltage then it's your Battery.

Use a fully charged Li-Po (preferably NOT the JetCat one), make sure is has a High C Rating (35+), and plug this directly into your ECU. For the TEST do NOT go through any I/O Boards or extension cables, just directly into the ECU and try another start.

You may think your ECU battery is good, BUT if it's just slightly down then you will get a WET Start (No Ignition), as the battery has to keep the Kero-Plug HOT, Cycle the Start Valve, and Run the Fuel Pump all at the same time. This can often results in No Ignition should the battery be tired.

Regards,

Darryl