I can confirm the tank solenoid and front one near the vaporizer are switching and working, iv changed the distributor with stepper motor etc as well and the vaporizer all of a car being broken, same fault same symptoms. been told its 02 sensor but i have no check engine light on? could this also be...

Newbie here, forgive any protocols missed. can anyone help me out here, my 2001 s40 factory fit lpg system is switching to petrol after 4 or 5 minutes, if I turn off lpg and then back on again via the switch it will go back to petrol in a second or 2, if I switch the ignition off and restart it will...