Being one of the original Toyota Industrial Truck employees, I have had to troubleshoot these many times. Take apart the LP solenoid valve and see if there is any rusty looking material in it. There is a filter in it. The bottom of the regulator has a drain plug. Open it and drain any residual oil from it. If nothing drains, it probably means it is gummed up. The secondary valve pressure should be 3.5~5.0 lbs/sq.in. The screw on the top of the regulator is an idle fuel mixture.