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-
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
2. Loosen the tube fitting at the cover of the hytrol
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-
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-
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
4. Remove the cover screws and the cover of the
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
3. Operate the SOPV manually as outlined in the
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
3. Inspect the secondary jet to make sure it is not
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
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
The correct setting of this valve is 2 1/2 psi
higher than the pressure setting of the pressure-reducing
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.