Service Manual

ISB, ISBe and QSB (Common Rail [...] Air in Fuel
Section 6 - Injectors and Fuel Lines - Group 06 Page 6-5
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Air in Fuel (006-003)
General Information
A replacement of fuel supply lines, fuel filters, fuel
injection pump, high-pressure fuel lines, and injectors will
let air enter the fuel system. Air in the system can make
the engine hard to start, run rough, misfire, produce low
power, or can cause excessive smoke and a fuel knock.
A few bubbles exiting the line during the test is expected.
A foamy appearance is indication of a leak that allows air
to enter, a severe inlet restriction that causes cavitation,
or a system that is not yet primed. If fuel inlet restriction
(Refer to Procedure Procedure 006-020) is not excessive,
the source of air entry should be isolated to one of the
following:
• Suction fuel lines
• ECM cooling plate assembly (if applicable)
• OEM fuel lines
• Suction-side fuel filter assemblies
• Stand-pipe(s) in the fuel tank(s)
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.
Test
NOTE: On quick-disconnect fittings with a white tang;
push in the white tang to release the fuel line.
Install the fuel pressure gauge adapter service tool, Part
Number 3164044, between the ECM cooling plate and the
gear pump.
Operate the engine at idle and check for air bubbles in the
clear line.