what battery are you using i also had the same problem first i used a jetcat ecu battery pack .
but that diddent work because that is 7,2 volts then i used a lipo battery pack 2s1p 8,4 volts
that was shligtly better only fore the first start .
then i ended up using a lipo battery pac 3s1p 1500mah 12,4 volt then the problem was solved.

BUT CHECK YOUR MANUAL IT STATES WHAT BATTERY PACK YOU SHOULD USE .
IN THE MANUAL FOR THE BEHOTEC JB 130 IT STATES YOU SHOULD USE A 8 CEL NICAD BATTERY
OR A 3S1P LIPO PACK THE MAXIMUM RATED VOLTAGE FOR THE ECUIS 12 VOLTS SO YOU COULD TRY IT WITH A 3S1P LIPO PACK (BUT AT YOUR OWN RISK).
ALSO LOOK AT YOUR GAS PRESSURE FOR STARTING