hi all iv got a 95 xg ute dule fuel that sometimes chooses not to start

problem.
car wont fire at all but will turn over, sometimes has spark at the plugs and still wont fire
wont fire on petrol or gas then an hour or so later it will run fine without doing anything to it im guessing it could be the smart lock as sometimes when i turn the key theres nothing and turn it off and turn it on and it starts but everyone ive taken it to has dismissed this as a problem and told me it could be any of these following problems:

not running on lpg causes:
*have been told the converter could be blocked due to corrosion
*told the switches on the gas system are dodgey (racv tested and said they are working)
*told it could be my spark plugs ( replaced and gapped to 0.8mm 2 weeks ago)
*told it could be my leads ( replaced 2 weeks ago)
*told it could be my dizzy cap or rotor button (both replaced 6 months ago)
*told by ezy gas that it could be my thermostat so they kindly charged me 35 bucks to replace it

not running on petrol causes:
*told it could be my injectors (swaped from a running xg i had)
*told it could be fuel filter ( replaced 2 months ago)
*told it could be the fuel pump ( replaced 2 months ago)
*told it could be a dirty tank (removed pressure cleaned and heat dried 2 months ago)

any alternate suggestions not reguarding plugs or leads would be great

cheers

Check you coil.

cheers
i havent replaced it in the 4 years iv had it so might replace it
replace with same type? or open to recomendations for a better one

cheers.

replace the coil with a new one they change the coil a bit now and much better and if not that then check ur relays and fuses