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M48 Tank
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10.8. There are two lines exiting the pressure regula-
tor. One is a regulated pressure line that feeds
the fuel rail via the fuel filter. The second line is
a return line. The third line is a high pressure
feed from the fuel pump. See Figure 10.8.
NOTE: There are two potential failure modes for
pressure regulators. They may reduce the pres-
sure too far, or they may not reduce the pressure
far enough. The second mode is more common.
NOTE: If too much pressure is delivered to the
injectors, the engine will run extremely rich. The
problem will be very pronounced at idle, but will
clear up to some extent under high load / open
throttle conditions.
NOTE: When an engine has run dramatically
rich, correct the core problem and change the oil
before continued operation. Oil dilution that may
result from the rich condition may cause hydro-
lock and/or catastrophic engine failure.
NOTE: Check fuel pressure by connecting a fuel
pressure gauge of adequate range (eg. NAPA /
Balkamp part number BK.700-1089) to the
shrader valve on the fuel rail. This will check
regulated fuel pressure. If fuel pressure at the
shrader valve is below 36 PSI, isolate the fuel
pump, and check output pressure and volume.
Figure 10.8
High pressure
from fuel pump
Regulated pressure
to rail, via filter
Return
to tanks
Vacuum barb
(not used
for this
application)
10.9. The fuel filter is easily accessible.
See Figure 10.9.
NOTE: Use only identical factory replacement
fuel filters. Filters that are not capable of func-
tioning at 3 bar. may rupture, leak, or disinte-
grate internally.
NOTE: Prime the fuel filter with a few ounces of
fuel when installing it. The initial pressure surge
into a dry filter may damage filtering medium.
NOTE: Fuel filters should be replaced at regular
intervals specified in the Operator’s Manual. A
blocked fuel filter puts extra load on the pump.
creating extra heat. This may lead to shortened
fuel pump life. Fuel pumps are much more
expensive than fuel filters. A blocked filter may
not present symptoms until the blockage is sub-
stantial enough to damage the fuel pump.
10.10.After the filter, the fuel reaches the fuel rail. The
fuel rail feeds the injectors. See Figure 10.10.
Figure 10.9
Fuel filter
To fuel rail
From
pump