2. Be sure the inlet pressure is high enough to maintain the required delivery pressure. Inlet pressure should be at least 10 pounds higher than desired deliv- ery pressure. 3. Check to see if the protective housings are miss- ing or damaged. If they are, this may indicate improper adjustment of the control valves. 4. Be sure that no part of the control valve system has been removed, disturbed, or damaged. The above checks may indicate the probable source of trouble. If not, the step-by-step procedures outlined in the following paragraphs should be fol- lowed. As always, when actually troubleshooting equipment, refer to the applicable technical manual. FUELING VALVE FAILS TO OPEN.— If the SOPV is not operating properly, proceed as follows: 1. Energize SOPV and apply pressure at the main valve inlet. 2. Loosen the tube fitting at the cover of the hytrol valve. 3. If fuel under pressure is present, the SOPV is probably stuck in the deenergized position. 4. Operate the SOPV manually as outlined in op- erating instructions. 5. If fuel under pressure at the loosened fitting is shut off when the SOPV is actuated manually, the SOPV must be repaired or replaced. If the hytrol valve fails to open, proceed as fol- lows: 1. Loosen the tube nut at the cover of the valve. No pressure should be present at this point. 2. Make sure there is no pressure in the down- stream fueling line. Break the union between the fueling pressure-relief control valve and the hytrol valve. 3. If no pressure is present at the disconnected union, failure of the diaphragm in the hytrol valve is indicated. 4. Remove the cover screws and the cover of the hytrol valve. 5. Remove the diaphragm assembly and replace the diaphragm if ruptured. 6. Reassemble the hytrol valve. Reconnect the un- ion and tubing fittings. FUELING VALVE FAILS TO CLOSE.— If the SOPV is not operating properly with the solenoid de-energized and pressure at the main valve inlet, proceed as follows: 1. Loosen the tube nut at the cover of the hytrol valve to determine whether or not fuel is under pressure at the loosened connection. 2. If there is no flow under pressure, SOPV failure is indicated. 3. Operate the SOPV manually as outlined in the operating instructions. 4. If pressure is received at the loosened tube con- nection when the SOPV is actuated manually, this indi- cates the SOPV must be replaced or repaired. The ejector-strainer may be clogged. Carry out the following procedure: 1. With no pressure at the valve inlet, remove the large box nut on the end of ejector-strainer. 2. Inspect the screen and clean it if it appears to be clogged. 3. Inspect the secondary jet to make sure it is not plugged. FUELING VALVE FAILS TO MAINTAIN DESIGNED DELIVERY PRESSURE.— If the pressure-reducing control valve is not operating prop- erly, carry out the following procedures: 1. Remove the adjusting screw housing. 2. Loosen the jam nut and turn the adjusting screw clockwise. 3. If the fueling valve opens during this procedure and delivers fuel at art increased and constant pressure, it is an indication the pressure adjustment of the pres- sure-reducing control valve is incorrect. 4. To remedy, follow the entire “Pressure Setting Procedure” outlined in the operating instructions. Fueling pressure-relief control valve may be held open. —The correct setting of this valve is 2 1/2 psi higher than the pressure setting of the pressure-reducing control valve. —If the fueling pressure-relief control valve is adjusted to a pressure equal to or lower than the desired delivery pressure, the fueling pressure-relief control valve will be held open. If it is open, inlet pressure will flow into the cover chamber of the fueling valve and hold it closed. 5-9