ISC, ISCe, QSC8.3, ISL, ISLe3, ISLe4 and QSL9 Engines – 006-003   Air in Fuel

Obtain a 1.09 mm [0.043 in] orificed diagnostic fuel line, Part Number 3164621.

A 1.09 mm [0.043-inch] orificed diagnostic fuel line is used in procedures to create rated flow through the low pressure fuel system, without the need to operate the engine under load.

Obtain a container suitable for collection of fuel that exits the diagnostic fuel line (a 19 liter [5 gal] bucket is recommended).

Construct a sight tube (CAPS) fuel systems only):

Assemble two (one male and one female, 7.8-14 thread barb-tite fittings and hose clamps to a 61 cm [2 ft] long number-10 clear hose approved for use with diesel fuel.

If 1.09 mm [0.043 in] orificed diagnostic fuel line, Part Number 3164621 can not be obtained, construct a 1.09 mm [0.043 in] orificed diagnostic fuel line, use the following steps:

Tap a female quick connect, Part Number 3376859.

Tap size 8-36 national fine (U.S.).

WARNING  Wear appropriate eye and face protection when using compressed air. Flying debris and dirt can cause personal injury.

Clean the female quick connect, Part Number 3376859, with compressed air.

Assemble a 1.09 mm [0.043 in] injector orifice, Part Number 3045018, with washer, to the female quick connect, Part Number 3376859.

NOTE: To obtain correct flow, use a 1.09 mm [0.043 in] injector orifice, Part Number 3045018.

Attach the orifice to an appropriate length (it must reach from the fuel pump to the fuel tank) of 1/4-inch, or larger, tubing.

NOTE: It is recommended that this tool be marked and identified as having a 1.09 mm [0.043 in] orifice installed. This is to make sure that there is no confusion when using this tool in the future.

Attach the 1.09 mm [0.043 in] diagnostic fuel line at the fuel injection pump’s diagnostic fitting.

Run the outlet of the diagnostic fuel line into the fuel collection container (or the vehicles fuel tank).

Install the sight glass between the fuel filter head and the fuel injection pump inlet.

Run the engine from idle to high idle several times to purge the air induced while installing the diagnostic fuel line.

Run the engine up to high idle while another technician checks for air in the system.

NOTE: A small amount of air in the inlet line is acceptable. Ignore any air that is observed in the tube running back to the fuel tank.

Operate the engine at idle and observe any air in the fuel supply. If air is observed, isolate the air to the following components:

• Fuel filter assembly
• Fuel heater
• Fuel lift pump assembly
• OEM fuel plumbing
• Fuel tank stand-pipe.

NOTE: A symptom of air-in-fuel for the engines equipped with a common rail fuel system is an audible surge associated with fuel system pressure fluctuations, due to air in the fuel supply.

The following test method will simulate rated fuel flow through the system so that air in fuel problems may be diagnosed.

Install a Compuchek™ fitting, Part Number 3824842, at the inlet to the 2 micron fuel filter and attach the 1.09 mm [0.043 in] diagnostic fuel line.

NOTE: If there is not enough clearance to install the female Compuchek™ fitting, Part Number 3824842, an adapter fitting, Part Number 3932302, and an 1/8-NPT male Compuchek™ fitting, Part Number 3377244, can be used to aid accessibility.

Route the outlet of the 1.09 mm [0.043-inch] diagnostic fuel line into a collection device of suitable size (a 19 liter [5 gal] bucket is recommended).

Start the engine and run the engine speed from idle to high idle several times to purge the air introduced while installing the diagnostic fuel line.

Observe the fuel flow exiting the diagnostic fuel line while the engine runs at idle speed.

Bubbles are an indication of a leak that allows air to enter, a severe inlet restriction that causes cavitation, or a system that is not yet primed. Refer to Procedure 006-020 Section 6.

• Suction fuel lines
• ECM cooling plate assembly
• OEM fuel lines
• Suction-side fuel filter assemblies
• Stand-pipe(s) in the fuel tank(s).

• Remove all test fuel lines. Refer to Procedure 006-024 in Section 6.
• Operate the engine and check for leaks.