Fuel Pressure Regulator - Kohler LH630-775 Service Manual

Service
The fuel pumps are non-serviceable and must be
replaced if determined to be faulty. If a fuel delivery
problem is suspected, make certain the pump is being
activated through the relay, all electrical connections
are properly secured, the fuses are good, and a
minimum of 7.0 volts is being supplied. If during
cranking, voltage drops below 7.0 volts, a reduction of
fuel pressure may occur resulting in a lean starting
condition. If required, testing of the fuel pump and
relay may be conducted.
1. Connect the black hose of Pressure tester (part of
EFI Service Kit, see Section 2) to the test valve in
the fuel rail. Route the clear hose into a portable
gasoline container or the equipment fuel tank.
2. Turn on the key switch to activate the pump and
check the system pressure on the gauge. If a
system pressure of 39 psi ±3 is observed, the
relay, fuel pump, and regulator are working
properly. Turn the key switch off and depress the
valve button on the tester to relieve the system
pressure.
a. If the pressure is too high, and the regulator is
outside the tank (just down line from the
pump), check that the return line from the
regulator to the tank is not kinked or blocked.
If the return line is good, replace the regulator
(see ''Regulator Service'' on page 5B.18).
b. If the pressure is too low, install in-line ''T''
between the pump and regulator and retest
the pressure at that point. If it is too low there
also, replace the fuel pump.
3. If the pump did not activate (step 2), disconnect
the plug from the fuel pump. Connect a DC
voltmeter across the terminals in the plug, turn
on the key switch and observe if a minimum of 7
volts is present. If voltage is between 7 and 14,
turn key switch off and connect an ohmmeter
between the terminals on the pump to check for
continuity.
a. If there was no continuity between the pump
terminals, replace the fuel pump.
b. If the voltage was below 7, test the wiring
harness and relay as covered in the
''Electrical Relay'' section.
4. If voltage at the plug was good, and there was
continuity across the pump terminals, reconnect
the plug to the pump, making sure you have a
good connection. Turn on the key switch and
listen for the pump to activate.
a. If the pump starts, repeat steps 1 and 2 to
verify correct pressure.
b. If the pump still does not operate, replace it.

Fuel Pressure Regulator

Figure 5B-21. External Fuel Pressure Regulator
with Base.
General
The fuel pressure regulator assembly maintains the
required operating system pressure of 39 psi ± 3. A
rubber-fiber diaphragm (see Figure 5B-22) divides the
regulator into two separate sections; the fuel chamber
and the pressure regulating chamber. The pressure
regulating spring presses against the valve holder
(part of the diaphragm), pressing the valve against
the valve seat. The combination of atmospheric
pressure and regulating spring tension equals the
desired operating pressure. Any time the fuel
pressure against the bottom of the diaphragm exceeds
the desired (top) pressure, the valve opens, relieving
the excess pressure, returning the excess fuel back to
the tank.
Section 5B
EFI Fuel System
5B.17
5B