I wonder if anyone can suggest a solution for me, I have a Saab 9-5 Aero which has been converted for around 7 years and runs sweetly on LPG or petrol. However, recently it will not change over to gas, and acts as if the gas has run out i.e. alarm beep then flashing green light. If i press the switch to petrol, then back to gas again it usually won't kick back into gas again, but if i leave it a while then repeat the process it sometimes goes back on to gas after several attempts, but sometimes not. The problem seems to be random, though at various times i have convinced myself it has something to do with holding the engine under load while i switch it over, which then proves completely ineffective the next time! It has been doing this for a couple of months now, and once it is fully warmed up on a long journey, it can sometimes run on gas for many miles without a problem, sometimes it has done 90-100 miles, then just as i convince myself it has righted itself, off it goes again and won't change over!
I have had a mobile LPG specialist look at it, and he was very helpful, giving the system a service while trying a few things, we changed the front solenoid because my old one was cracked, then after driving it whilst connected to the diagnostics, it appeared the pressure was dropping and rising, so i ordered a MAP sensor (ESGI) from Germany but when i tried it, it is exactly the same! So, if the pressure really is fluctuating, what might cause this? I know the rear solenoid is operating OK, I have occasionally caught a whiff of LPG smell, but no different from normal, the injectors are relatively new, i think the vaporiser is the original, the switch sometimes won't respond to the press of the button i.e won't come off gas setting (even though it isn't actually working, the green lights stay on and can't be cancelled, but leave it a few minutes and try again and it works again! I do know that each time the gas tries to cut in, the solenoid is operating OK, but the pressure seems to be inadequate, or the MAP sensor thinks it is, and that is why it seems to kick the system out like it has just run out of gas!
Sorry if this seems long-winded, i just wanted to mention some of the things i've tried in order to give an idea what i'm up against, it is one of those annoying problems that will probably right itself if i take it to be looked at!
Thanks for reading and hope someone can suggest something i can try?