Service Manual

Injector ISB, ISBe and QSB (Common Rail [...]
Page 6-68 Section 6 - Injectors and Fuel Lines - Group 06
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Injector (006-026)
General Information
WARNING
The fuel pump, high-pressure fuel lines, and fuel rail
contain very high-pressure fuel. Do not loosen any
fittings while the engine is running. Wait at least 10
minutes after shutting down the engine before
loosening any fittings in the high-pressure fuel
system to allow pressure to decrease to a lower level.
WARNING
Fuel may be returned at highly elevated temperatures.
Wear safety glasses and protective gloves and
clothing when performing this test. Avoid any contact
with returned fuel.
WARNING
The pressure within the fuel rail is extremely high. A
high-pressure leak can penetrate the skin. Stand clear
of the engine while it is running.
CAUTION
Be sure the fuel inlet and return valves are returned to
the open position before cranking the engine. Engine
damage can result if valves are in the wrong position
when the engine is cranked or started. Environmental
damage can also occur.
The fuel return manifold is located near the point at which
the OEM connects the vehicle fuel drain line. To locate
this manifold, follow the fuel drain lines from their source,
(rail pressure relief valve, injector return, or high pressure
injector pump return) to their termination point. The
termination point will occur at the fuel return manifold.
Refer to Procedure 006-999 in Section 6.
An internal leak from either the high-pressure connector
or the fuel injector will result in increased fuel return flow
from the cylinder head. The single cylinder cut-out test will
not be able to isolate this leak because it occurs before it
reaches the control needle inside the injector. Because all
injectors share the same pressurized fuel supply from the
rail, all cylinders will share the loss of fuel equally.
Due to the varying engine configurations, the following
steps have been established to cover a majority of engine
configurations. The purpose of the following steps are to
isolate and measure the injector return fuel drain flow. In
some configurations this requires isolating the high-
pressure fuel pump and/or fuel rail pressure relief valve
fuel drain flows.