Manufacturer communication — 2001 GMC THE 4.8L RPO LR4 (VIN V), 5.3L RPO LM7 (VIN T), AND 6.0L RPO LQ4 (VIN U) (YUKON)

• In 2001 the Gen III engine family was the 4.8L RPO LR4 (VIN V), the 5.3L RPO LM7 (VIN T) and the 6.0L RPO LQ4 (VIN U); for 2002 the 6.0L RPO LQ9 (VIN N) and the 5.3L L59 (VIN Z) are being added.

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  In 2001 the Gen III engine family was comprised of the 4.8L RPO LR4 (VIN V), 5.3L RPO LM7 (VIN T), and 6.0L RPO LQ4 (VIN U). For 2002, the 6.0L RPO LQ9 (VIN N) and the 5.3L L59 (VIN Z) are being added to the list.

• The 5.3L L59 has an E85 compatible fuel system, which can handle fuel that is up to 85% ethanol. Its fuel system components are specially designed to survive in this environment. Because of this, fuel rail service is different from the other Gen III engines.

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  The 5.3L L59 is equipped with an E85 compatible fuel system, which can handle fuel that is up to 85% ethanol. Fuel system components are specially designed to survive in this environment. Because of this, fuel rail service is different from the other Gen III engines.

• For 2002, there will be early and late model intake air fuel modules (IAFM), consisting of the throttle body, fuel rail and injectors, and intake manifold. The early IAFMs will be the same as 2001.

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  For 2002, there will be early and late model intake air fuel modules (IAFM), consisting of the throttle body, fuel rail and injectors, and intake manifold. The early IAFMs will be the same as 2001.

• The PCV valve will be changed from a variable valve to a fixed orifice.

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  The PCV valve will be changed from a variable valve to a fixed orifice.

Steps to confirm (in the document’s order)

• The fuel pressure is different for this application (the E85 fuel rail): 334 to 375 kPa (48 to 54 psi).

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  The fuel pressure regulator is also specific to the E85 fuel rail. It is larger in diameter than those used in the other Gen III engine applications and uses a special diaphragm that is compatible with E85 fuels. The fuel pressure is different for this application -- 334 to 375 kPa (48 to 54 psi).

Repair

• The late production IAFMs on engines that do not require EGR will have a cast-over EGR port. All service replacement manifolds for 2002 will have an open EGR port. If the manifold you are replacing does not have EGR, you must install the supplied plug and screw, following the instructions in the parts package.

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  Also the late production IAFMs on engines that do not require EGR will have a cast-over EGR port. All service replacement manifolds for 2002 will have an open EGR port. If the manifold you are replacing does not have EGR, you must install the supplied plug and screw, following the instructions in the parts package.

Parts

• The L59 uses Denso injectors, which are not interchangeable with the Multec 2 injectors used in the other Gen III applications.

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  The L59 uses Denso injectors that are not interchangeable with the Multec 2 injectors used in the other Gen III applications.

• Because of this, the right fuel rail, left fuel rail and fuel crossover pipe are available only as a complete assembly.

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  Because of this, the right fuel rail, left fuel rail and fuel crossover pipe are available only as a complete assembly.

• The fuel pressure regulator is also specific to the E85 fuel rail. It is larger in diameter than those used in the other Gen III engine applications and uses a special diaphragm that is compatible with E85 fuels.

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  The fuel pressure regulator is also specific to the E85 fuel rail. It is larger in diameter than those used in the other Gen III engine applications and uses a special diaphragm that is compatible with E85 fuels.

Caution

• If you replace the O-rings, be sure they are specific to this injector. The Denso injector is longer than the Multec 2.

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  If you replace the O-rings, be sure they are specific to this injector. Also notice that the Denso injector is longer than the Multec 2.

• The L59 fuel rail is made of a special material that is resistant to degradation from E85 fuel. Special thread-cutting screws hold the fuel crossover in place. Do not remove these screws. Re-installing them will cut new threads, destroying the former threads and creating a possibility of failure.

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  The L59 fuel rail is made of a special material that is resistant to degradation from E85 fuel. Special thread-cutting screws hold the fuel crossover in place. Do not remove these screws. Re-installing them will cut new threads, destroying the former threads and creating a possibility of failure.

• Three different fuel pressure regulators are used this year. Each one is held in place on the fuel rail by a unique retainer, and the retainer diameter and window dimensions are different for each. Use the correct retainer to ensure adequate retention of the fuel pressure regulator.

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  Three different fuel pressure regulators are used this year. Each one is held in place on the fuel rail by a unique retainer. The retainer diameter and window dimensions are different for each. Use the correct retainer to ensure adequate retention of the fuel pressure regulator.