C7 Industrial Engines Testing and Adjusting – Air Inlet and Exhaust System – Inspect

Air Inlet Restriction

There will be a reduction in the performance of the engine if there is an excess restriction in the air inlet system or the exhaust system.

Table 1

Required Tools
Part Number	Part Name	Quantity
1U-5470 or 198-4240	Engine Pressure Group or Digital Pressure Indicator	1

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 Group ” for the instructions that are needed to use the 198-4240 Digital Pressure Indicator .

 

1. Check the Air Filter Change Indicator Gp on the air inlet for a reading of the restriction.

2. Inspect the engine air cleaner inlet and ducting in order to ensure that the passageway is not blocked or collapsed.

3. Check for dirt tracks on the clean side of the engine air cleaner element, the air inlet hose, and the clamps. If dirt tracks are observed, contaminants are flowing past the engine air cleaner element, the seal for the air cleaner, and/or the air inlet hose.

4. Inspect the engine air cleaner element. Replace a dirty engine air cleaner element with a clean engine air cleaner element.
5. Use the differential pressure gauge of the 1U-5470 Engine Pressure Group or the 198-4240 Digital Pressure Indicator .

Illustration 2 g01176673
Air inlet system (typical example)

(1) Turbocharger

(2) Air Inlet Piping

(3) Test location

(4) Air cleaner

Connect the vacuum port of the differential pressure gauge to test location (3) . Test location (3) can be located anywhere along air inlet piping (2) after engine air cleaner (4) but before turbocharger (1) .
The air flow through a new engine air cleaner element must not have a system restriction of more than the following amount:

Maximum restriction … 3.7 kPa (15 inch of H2O)
The air flow through a used engine air cleaner may have an additional restriction. The air flow through a plugged engine air cleaner will be restricted to some magnitude. In either case, the restriction must not be more than the following amount:

Maximum restriction … 6.2 kPa (25 inch of H2O)

Exhaust Restriction

Excessive idling can cause the muffler, the catalytic converter/muffler, or the diesel particulate filter to plug. A plugged muffler, a plugged catalytic converter/muffler, or a plugged diesel particulate filter will lead to an increase in exhaust back pressure. Operating the engine in extremely cold conditions may cause the muffler, the catalytic converter/muffler , or the diesel particulate filter to plug. One indication of a plugged muffler, catalytic converter, or diesel particulate filter is poor engine response.

Exhaust Back Pressure for Mufflers and Catalytic Converters
Back pressure is the difference in the pressure between the exhaust and the atmospheric air.

Table 2

Tools Needed
Part Number	Part Name	Quantity
1U-5470 or 198-4240	Engine Pressure Group or Digital Pressure Indicator	1

If the exhaust is not equipped with a back pressure tap, the following procedure may be use in order to install a pressure tap. Refer to Truck Engine News, SEBD6729, “Measuring Exhaust Back Pressure” for measuring the back pressure at a proper test location.

Use the differential pressure gauge of the 1U-5470 Engine Pressure Group or the 198-4240 Digital Pressure Indicator in order to measure back pressure from the exhaust. Use the following procedure in order to measure back pressure from the exhaust:

High Idle (Plugging) Test

Illustration 3 g01451109
Exhaust system (typical example)

(1) Turbocharger

(5) Muffler

(6) Test location

(7) Exhaust piping

Note: Do not try to burn out a plugged muffler. The muffler can become severely overheated. This will cause other system components to fail.

 

1. Inspect the system components for any noticeable damage that would cause a restriction.

 

2. Connect the pressure port of the differential pressure gauge to test location. Refer to Truck Engine News, SEBD6729, “Measuring Exhaust Back Pressure” for measuring the back pressure at a proper test location.

 

3. Leave the vacuum port of the differential pressure gauge open to the atmosphere.

 

4. Start the engine. Run the engine in the no-load condition at high idle until the engine reaches normal operating temperature.

 

5. Record the value.

 

6. Multiply the value from Step 5 by 1.8.

 

7. Compare the result from Step 6 to the value that follows.

Back pressure from the exhaust must not be more than the following amount:

Maximum back pressure for engines with a standard muffler … 10 kPa (40 inch of H₂O)

Maximum back pressure for engines with a catalytic converter/muffler … 15 kPa (60 inch of H₂O)

If the maximum back pressure is within the allowable limits, refer to Troubleshooting, “Low Power/Poor or No Response to Throttle”.

If the back pressure exceeds 15 kPa (60 inch of H₂O), replace the muffler.

Full Load Test

Note: Do not try to burn out a plugged muffler. The muffler can become severely overheated. This will cause other system components to fail.

 

1. Check the arrangement number of the engine and verify that all components are correct.

Note: Run the vehicle on a dyno up to 30 minutes in order to reach operating temperature. Monitor all of the engine components for any signs of overheating.

 

2. Measure the back pressure at a full load and full speed.

 

3. Record the results.

 

4. The back pressure for the catalytic converter/muffler is at 15.0 kPa (60 inch of H₂O).

 

5. Replace any components that have been proven damaged.

Exhaust Back Pressure for Diesel Particulate Filters (If Equipped)

High Idle (Plugging) Test

Illustration 4 g01451160
Diesel particulate filter (typical example)

(8) Inlet section

(9) Catalyst section

(10) Filter section

(11) Outlet section

(12) Test location

(13) Tee fitting

(14) Copper tubing

(15) Thermocouple

Note: Limit the idle time of the engine to 20 minutes. If large quantities of soot are accumulated in the diesel particulate filter, running the engine can permanently damage the filter and other components. Avoid continuous idle time of the engine by using the idle shutdown timer. Refer to Troubleshooting, “Idle Shutdown Timer – Test” for using the idle shutdown timer.

Note: Do not test the exhaust back pressure if the red warning light has been activated. Clean the Diesel particulate filter immediately.

Note: Refer to Special Instruction, REHS1807, “Installation Guide for Diesel Particulate Filters” for properly cleaning the diesel particulate filter.

 

1. Inspect the system components for any noticeable damage that would cause a restriction.

 

2. Connect the pressure port of the differential pressure gauge to test location. Refer to Truck Engine News, SEBD6729, “Measuring Exhaust Back Pressure” for measuring the back pressure at a proper test location.

 

3. Leave the vacuum port of the differential pressure gauge open to the atmosphere.

 

4. Start the engine. Run the engine in the no-load condition at high idle until the engine reaches normal operating temperature.

 

5. Record the value.

 

6. Multiply the value from Step 5 by 1.8.

 

7. Compare the test result to the value that follows.

Clean the diesel particulate filter if the back pressure exceeds the following value.

Maximum back pressure for engines with a Diesel Particulate Filter … 25 kPa (100 inch of H₂O)

 

Full Load Test

Limit the idle time of the engine to 20 minutes. If large quantities of soot are accumulated in the diesel particulate filter, running the engine can permanently damage the filter and other components. Avoid continuous idle time of the engine by using the idle shutdown timer. Refer to Troubleshooting, “Idle Shutdown Timer – Test” for using the idle shutdown timer.

Note: Do not test the exhaust back pressure if the red warning light has been activated. Clean the diesel particulate filter immediately.

Note: Refer to Special Instruction, REHS1807, “Installation Guide for Diesel Particulate Filters” for properly cleaning the diesel particulate filter.

 

1. Check the arrangement number of the engine and verify that all components are correct.

Note: Run the vehicle on a dyno up to 30 minutes in order to reach operating temperature. Monitor all of the engine components for any signs of overheating.

 

2. Measure the back pressure at a full load and full speed.

 

3. Record the results.

 

4. The back pressure for the diesel particulate filter is at 25 kPa (100 inch of H₂O).

 

5. Replace any components that cannot be cleaned. Replace any components that are proven faulty.