86 3.5 EFI wont run on petrol but fine on LPG

Hello peeps, i need help!!
But apart from that, my 86 3.5 EFI rangie is giving me lots of grief at the mo!! It starts OK on petrol but as soon as any temp gets into the engine it cuts out and wont run. Well, i can get it to run if i hold the loud pedal right down, it then simply splutters and pops from the air flow meter, but will not tick over on its own.

It runs fine and dandy on LPG though !!! I have replaced the water temp sender as i was told that was defiantly the problem but that didn't work. I have tried 2 fuel pumps and 2 different air flow meters, changed the fuel filter and drained the tank( what came out was very manky looking!!) but still no joy

As well as the popping from the air flow meter it also whistles when i try and rev it Switch over to LPG and it instantly runs fine!!

Any help and info would be very much appreciated.

Cheers,
Stu

Hi, since the system runs fine on LPG this should eliminate the ignition side, if your tank was dirty it is probably up the line, injectors blocked ?. It sounds like its starting and running on the cold start injector as said earlier.

Thanks for the replies

Il try starting it in the morning with the cold start disconnected and see if it struggles to start. How do i flush the fuel lines out? And how easy is it to clean the injectors out?

Thanks,
Stu