Service Manual

Fuel Drain Lines ISB, ISBe and QSB (Common Rail [...]
Page 6-22 Section 6 - Injectors and Fuel Lines - Group 06
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If the fuel drain line restriction is too high, check the
original equipment manufacturer's fuel lines to the tank for
proper size, leaks, bends, or clogs.
Check the fuel drain valves for restrictions for plugging.
Check for possible plugged fuel tank vents.
Fuel Drain Lines (006-013)
General Information
Due to the number of different fuel line routing and
connector styles, the steps in this procedure have been
written to be generic. Some of the illustrations may not
represent the parts being removed or installed.
The fuel drain line restriction is measured at a fuel return
manifold 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.
NOTE: All engines have three fuel drain lines as follows:
(1) from the injector return port in the cylinder head to the
combined fuel manifold, (2) from the high-pressure fuel
pump to the combined fuel manifold, and (3) from the fuel
pressure relief valve to the combined fuel manifold.
NOTE: For marine applications, there is a fourth fuel drain
line: (4) from the combined fuel manifold to the fuel cooler.
CAUTION
Use caution when disconnecting or removing fuel
lines, replacing filters and priming the fuel system,
that fuel is not spilled or drained into the bilge area.
Do not drop or throw filter elements into the bilge
area. The fuel and fuel filters must be discarded in
accordance with local environmental regulations.
WARNING
Be sure that the fuel inlet and return valves are
returned to the open position before cranking engine.
Engine damage can result if valves are in the wrong
position when engine is cranked or started.
Environmental damage can also occur. Refer to
Procedure Procedure 005-999 (Fuel System Overview)
in Familiarization section for further information.