2004/04/01 Caterpillar

Truck Engines:

3116 (S/N: 8WL1-UP; 2CW1-UP)

3126 (S/N: 1WM1-UP; 4ES1-UP; 1BW1-UP; 8HW1-UP; 7LZ1-UP)

3126B (S/N: BKD1-UP; 1AJ1-UP; 5GL1-UP; 8YL1-UP; 7AS1-UP; 6PZ1-UP; 7JZ1-UP; 8SZ1-UP)

3126E (S/N: DPF1-UP; LEF1-UP; CKM1-UP; CRP1-UP; 9SZ1-UP)

The 122-5053 Solenoid Valve Gp (INJECTION ACTUATION PRESSURE CONTROL VALVE) in the 3126B engine controls the oil pressure that is provided to the Hydraulic Electronic Unit Injector (HEUI). Reports of the 122-5053 Solenoid Valve Gp (INJECTION ACTUATION PRESSURE CONTROL VALVE) have shown dirt, debris, or oil sludge that will cause the spool in the valve to stick. This will cause the control valve to operate erratically.

The erratic operation of the control valve will cause variations in oil pressure in the HEUI. The variations in oil pressure in the HEUI can result in the following:

• Idle instability

• Engine knock

• Hard starting

Also, there could be other causes of these symptoms. Follow the diagnostic procedure in the proper electronic troubleshooting guide for active engine fault codes. If the 122-5053 Solenoid Valve Gp (INJECTION ACTUATION PRESSURE CONTROL VALVE) is the suspected problem, follow the"Injection Actuation Pressure Test". This test is described in the engine troubleshooting guide. Failure to follow this procedure may result in an incorrect diagnosis.

Dirt or debris that is found in engine oil could be a result of the following:

• Contaminated tanks

• Dirty oil containers

• Dirty funnels

• Dirty hoses or other equipment that dispenses oil

Sludge that is found in the engine oil can be a result of excessive oil change intervals or oils that do not meet Caterpillar recommendations. Refer to the Operation Manual for recommended oil specifications and change intervals.

Caterpillar suggests using the recently announced High Efficiency engine oil filter. The new High Efficiency engine oil filters provide significant improvements in engine oil filtration. This is compared to previous standard engine oil filters. The new filters are now used in production of new engines which replaces the former standard oil filters. The new filters are also available as optional parts service replacements for the standard efficiency oil filters. The previous part number and the new part number for the oil filters are shown in the chart below:

If you replace the 122-5053 Solenoid Valve Gp (INJECTION ACTUATION PRESSURE CONTROL VALVE), Caterpillar suggests installing the new stiffer 242-3864 Spring in the oil filter bypass valve of earlier engines. The oil filter bypass valve is located in the oil filter base assembly. The filter bypass valve allows the oil to bypass the engine oil filter when the oil is too thick, or if the oil filters become excessively plugged. The stiffer 242-3864 Spring increases the amount of filter restriction that is needed to open the oil filter bypass valve.

The previously announced 242-3864 Spring for the engine oil bypass valve replaces the 9L-9188 Spring in new engines. The new 242-3864 Spring is adaptable to all earlier HEUI engines that are listed in the following chart:

Illustration 1	g01058856
Typical example of the 242-3864 Spring (1) location in the Oil Filter Base