C12 Marine Engine Caterpillar

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 TMI (Technical Marketing Information). The information is also listed on the Fuel Setting and the Service Information System. 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 (Technical Marketing Information). The correct pressure is also on the Fuel Setting And the related Service Information System. 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 (Technical Marketing Information). The pressure will also be less than the pressure that is listed on the Fuel Setting And the Related Service Information System. If the fuel is rated below 35 API, the inlet manifold pressure can be more than the pressure listed in the TMI (Technical Marketing Information). The pressure will also be more than the pressure that is listed on the Fuel Setting And the Related Service Information System.

Note: Ensure that the air inlet and the exhaust are not restricted when you are checking the inlet manifold pressure.

Illustration 1	g00854951
Pressure test location on inlet manifold (1) Plug

Table 1

Tools Needed
Part Number	Part Name	Quantity
1U-5470	Engine Pressure Group	1

Illustration 2	g00293196
1U-5470 Engine Pressure Group

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 .

Use the following procedure in order to measure the inlet manifold pressure:

1. Remove plug (1) from the inlet manifold.

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

3. Record the value.

4. Compare the value that was recorded in Step 3 to the pressure that is given in the TMI (Technical Marketing Information). The correct pressure is also given in the Fuel Setting And Related Information Microfiche.