C15 On-Highway Engine Caterpillar

Refer to Special Instruction, SEHS8907, "Using the 1U-5470 Engine Pressure Group " for the instructions that are needed to use the 1U-5470 Engine Pressure Group . Refer to Operation Manual, NEHS0818, "Using the 198-4240 Digital Pressure Indicator " for the instructions that are needed to use the 198-4240 Digital Pressure Indicator .

The efficiency of an engine can be checked by making a comparison of the pressure in the inlet manifold with the information given in the Technical Marketing Information (TMI). This test is used when there is a decrease of horsepower from the engine, yet there is no real sign of a problem with the engine.

The correct pressure for the inlet manifold is listed in the TMI. Development of this information is performed under the following conditions:

• 99 kPa (29.7 in Hg) dry barometric pressure

• 29 °C (85 °F) outside air temperature

• 35 API rated fuel

On a turbocharged, aftercooled engine, a change in the fuel rating will change the horsepower. A change in the fuel rating will change the inlet manifold pressure. If the fuel is rated above 35 API, the inlet manifold pressure can be less than the pressure given in the TMI. If the fuel is rated below 35 API, the inlet manifold pressure can be more than the pressure listed in the TMI.

Note: Ensure that the air inlet and the exhaust are not restricted when you check the inlet manifold pressure. Refer to Testing and Adjusting, "Air Inlet and Exhaust System - Inspect" for more information.

Use the following procedure in order to use an electronic service tool to measure the inlet manifold pressure:

1. Connect the electronic service tool.

2. Operate the engine under the suspect conditions.

3. Record the value.

4. Compare the value that was recorded in Step 3 to the pressure that is given in the TMI.

Use the following procedure in order to use the 1U-5470 Engine Pressure Group to measure the inlet manifold pressure:

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Illustration 1	g01098341
Pressure test location on the inlet manifold (1) Intake manifold air temperature sensor (2) Pipe plug

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Illustration 2	g00293196
1U-5470 Engine Pressure Group

1. Remove pipe plug (2) from the inlet manifold. Intake manifold air temperature sensor (1) does not need to be removed.

2. Connect the 1U-5470 Engine Pressure Group to the inlet manifold at the pressure test location.

3. Operate the engine under the suspect conditions.

4. Record the value.

5. Compare the value that was recorded in Step 4 to the pressure that is given in the TMI.