Rust Found In The Injector Inlet Filter Screen During Injector Repairs - keywords 4.8 5.3 6.0 contaminated contamination DTC engine fuel gas L33 LH6 line L59 LM7 LQ4 LQ9 LR4 misfire miss P0300 SES

This PI revision was made to update the repair procedures. Please discard PIP3280B.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Engine driveability concerns or misfire caused by clogged fuel injector inlet filter screens. In a returnless fuel system no fuel is sent back to the fuel tank from the engine. All fuel leaving the tank flows through the fuel injectors.

Any contamination (including rust) that forms in the fuel line will find its way to the fuel injectors. A screen at the inlet of the fuel injector filters out small contaminants, including rust. If enough debris accumulates on the injector filter, it will start to restrict flow.

When diagnosing driveability symptoms due to clogged fuel injectors, follow the procedures outlined in bulletin 03-06-04-030A. If the bulletin procedures lead to replacing an injector, inspect the removed injector for evidence of rust contamination. If rust is plugging the fuel injector, replace it, because a procedure for removing rust from the injector filter has not been developed.

If rust has accumulated at the injector inlet filter, there is a chance rust remains in the fuel lines, and the injector inlet filter may plug again. Whenever rust is observed in an injector, replacement of all steel lines is recommended. The fuel filter / pump assembly - located in tank - should also be inspected and replaced as necessary. Although the presence of rust in the fuel tank will be restricted to the dirty side of the filter, the same material that would lead to rust in the steel fuel lines will likely affect the uncoated portions of the fuel pump and filter assembly.

A small amount of rust in the fuel tank will typically not cause a problem. The fuel filter will prevent the rust from getting to the injectors. The capacity of the filter is large enough to keep it from plugging up. There is also a strainer at the inlet to the fuel pump. The strainer prevents contamination from getting into the fuel pump and causing problems. However, rust in the fuel tank is a sign that water may be in the tank. If rust is observed in the fuel tank, empty it and flush with clean fuel.

Note: Using GM Fuel System Treatment PLUS (at oil change intervals) can protect against the affects of water and certain contaminants that may be present in some poor quality fuels.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.