If it is an Asian gas regulator remove the six 10mm screws remove the plate,, I can't quite remember if there is now a disc to be removed if there is flick it out with a small screw driver once removed you will see a felt pad
Remove it and you may find a chamber full of solids. Remove solid with vacuum cleaner, if you have a new felt pad fit it if not clean the old one as best you can and fit it back in chamber reassemble unit and see if truck starts, there's also a gas adjustment screw on this unit screw it in to enriching gas and out to weaken mixture. I hope this is helpful.