18
Maintenance
Fuel Control System
This machine utilizes a fuel solenoid valve located on
the fuel pump to control the flow of fuel to the combus-
tion chamber. The solenoid, which is normally closed, is
activated by a flow switch when water flows through it.
When the operator releases the trigger on the spray
gun, the flow of water through the flow switch stops,
turning off the electrical current to the fuel solenoid.
The solenoid then closes, shutting off the supply of fuel
to the combustion chamber. Controlling the flow of fuel
in this way gives an instantaneous burn-or-no-burn situ-
ation, thereby eliminating high and low water tempera-
tures and the combustion smoke normally associated
with machines incorporating a spray gun. Periodic
inspection, to insure that the fuel solenoid valve
functions properly, is recommended. This can be done
by operating the machine and checking to see that the
burner is not firing when the spray gun is in the OFF
position.
When operating without the burner there must be
heating fuel in the fuel tank. Otherwise the fuel pump
has no lubrication and will run dry. This can cause
damage to the coupling and to the fuel pump.
Fuel Pressure Adjustment
To control water temperature, adjust fuel pressure by
turning the regulating pressure adjusting screw
clockwise to increase, counterclockwise to decrease.
Do not exceed 200 psi.
NOTE
: hen changing fuel pump, a bypass plug must
be installed in return port or fuel pump will not prime.
Burner Nozzle
Keep the tip free of surface deposits by wiping it with a
clean, solvent saturated cloth, being careful not to plug
or enlarge the nozzle. For maximum efficiency, replace
the nozzle each season.
Air Adjustment
Machines are preset and performance tested at the
factory - elevation 100'. A one-time initial correction for
your location will pay off in economy, performance, and
extended service life. If a smoky or eye-burning
exhaust is being emitted from the stack, two things
should be checked. First, check the fuel to be certain
that kerosene or No. 1 home heating fuel is being used.
Next, check the air adjustment on the blower assembly.
Karcher HDS 615-617 Operator’s Manual 9.800-103.0 - V
Downloaded from