Injector Misfire Due to Low/No Fuel Condition

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Injector Misfire Due to Low/No Fuel Condition

CONFIDENTIAL TIBU4276-00

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TECHNICAL INFORMATION BULLETIN	June 16, 2004
Truck Engines	C7 (KAL) C9 (9DG) C-9 (MTB)
	Component Code: 1290

SUBJECT: Injector Misfire due to Low/No Fuel Condition

PROBLEM:

Analysis of injectors returned from the field indicates that running the engine out of fuel, excessive air in the fuel, or high fuel inlet restriction may cause an internal injector failure. Multiple injectors failing the Cylinder Cutout Test in Caterpillar Electronic Technician (Cat ET) may indicate this mode of failure. If this occurs, debris from the internal injector failure may collect in the fuel return pressure regulator or fuel return screen (if equipped). See Figure 1.

SOLUTION:

If the Cylinder Cutout Test in Cat ET indicates that multiple injectors have failed, or if the engine has a recent history of injector failures, the fuel return pressure regulator and the fuel return screen need to be inspected for debris. See Figure 1.

Clean the fuel return screen (if equipped). If the engine is equipped with a fuel regulator that has a 90-degree elbow on the cylinder head, then there is a screen inside of the elbow. Remove the 90-degree elbow from the cylinder head and pressure regulator assembly. See Figure 1. Reverse flush any debris out of the elbow screen. If all of the debris cannot be removed from the elbow screen, then replace the 196-6838 90-degree elbow.

Clean/Replace the fuel return pressure regulator assembly as required. If the engine is equipped with a 90-degree elbow screen (see Step 2), the debris should have been caught by the screen. Only replace the 229-8870 pressure regulator if debris is visible on the inlet side of the pressure regulator. Replace failed injectors as indicated by the Cat ET Cylinder Cutout Test.

If the engine did not run out of fuel, make sure that the fuel inlet restriction measured at the fuel transfer pump inlet is within specification (max inlet restriction 4.1 in Hg or 14 kPa). Also, make sure that there is not excessive air in the fuel system by using a sight gauge on the fuel inlet and fuel outlet of the cylinder head. Make sure the fuel tank vent or cap is venting properly.

Note: There have been documented cases of pinched/restricted Original Equipment Manufacturer (OEM) fuel lines and air entry on OEM primary fuel filters.

If the fuel return pressure regulator or the elbow are replaced, return them to the Caterpillar claims room at the address below.

Caterpillar Service Claims Room 8201 N. University Peoria, IL 61615 USA Attn: Geoff Monari / Anant Kasture

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