Starting problem - Gas conversion ???

[eggybread]

hi, this is my 1st post.. just bought a lovely mk3 supra which has a gas conversion. you start it on petrol and flick a switch to gas when its warmed up a little. the guy i bought it off always switched it back to petrol before turning the car off. anyway, on 2 occasions it has not started and i think id forgot to switch it back to petrol before turning it off. the weird thing is that when i try to start it the starter motor doesn't even kick in and it just clicks once when i turn the key. this bit could be down to the battery but this has been changed since the first time however i did leave a light on all day yesterday and it ran the battery down. after jumping it i drove it to a few locations and stated ok. however, on the last attempt to start it after stopping for a matter of secons it just clicked again when i turned the key. i jumped it again and the starter moter was eaging but it would not start at all. i hadnt flooded it but after lots of attempts it sounded like petrol gradually got through and it started.. i had to pump the accelerator to do this. not sure if this all makes sense to anyone ! i believe it could be something on the fuel pump or gas conversion but that doesnt explain the battery needing a jump. does anyone know about gas conversions or have any clue whats going on ? its an automatic by the way and incase anyones interested.. it runs beautifully on gas and i get 210 miles on 20 pounds ! i well recommend a conversion. cheers for any help. eggybread !