COVER 2B3148 - Caterpillar

The efficiency of an engine can be checked by comparing the present inlet manifold pressure with the information given in the Technical Marketing Information (TMI). Perform this test when there is a decrease of horsepower from the engine, yet there is no real sign of a problem with the engine.The data for the engine from the engine test cell for the inlet manifold pressure is listed in the TMI. This data is collected under controlled conditions. Varying conditions will cause varying results. Refer to TMI for specific information.Any change from these conditions can produce a change in the inlet manifold pressure. The outside air may have a higher temperature and a lower barometric pressure than the controlled conditions. These conditions will cause a lower inlet manifold pressure measurement than the pressure that is provided in the TMI. Outside air that has both a lower temperature and a higher barometric pressure will cause a higher inlet manifold pressure measurement.Note: Be sure that the air inlet or the exhaust does not have a restriction when you are checking the pressure.Note: The Caterpillar Electronic Technician (ET) may be used to check the pressure in the inlet manifold.
Table 1
Tools Needed
Part Number Part Description
1U-5470
or
198-4240 Engine Pressure Group
or
Digital Pressure Indicator Gp
Illustration 1 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. Refer to Operation Manual, NEHS0818, "Using the 198-4240 Digital Pressure Indicator Gp" for the instructions that are needed to use the 198-4240 Digital Pressure Indicator Gp.
Illustration 2 g02017753
Test location for the inlet manifold pressure
Use the following procedure in order to measure the inlet manifold pressure:
Remove the inlet manifold pressure sensor from the cylinder head.
Install a T fitting into the port at the cylinder head.
Install the pressure sensor into one side of the T fitting.
Connect the 1U-5470 Engine Pressure Group into the other side of the T fitting. Note: In order for the engine to operate normally, the pressure sensor must be reinstalled onto the engine at this location.
Measure the inlet manifold pressure under similar engine conditions that are given in TMI. Record the value.
Compare the value that was recorded in Step 5 to the pressure that is given in the TMI.