My Monitor 21 has shutdown and is not getting fuel, I cleaned the fuel filter to no avail. I use the internal tanks. The reservoir is full and I have a shut off valve on the line from the reservoir to the filter. When I turn on the valve with the filter out, the fuel barely drips out of it. Is there another screen or something in the bottom of the reservoir or in the tube? I have a 422 heater with a similar starving for fuel problem.