Engine Performance Diagnostic Procedure

ENGINE PERFORMANCE DIAGNOSTIC PROCEDURE
The Engine Performance Diagnostic Procedure begins with those items which are the high frequency, easy-to-diagnose problems, and progresses to the low frequency, hard to diagnose problems. Use of this procedure will promote rapid as well as accurate diagnosis.

The Engine Performance Diagnostic Procedure follows, step by step, the Engine Performance Diagnosis. Each test step is labeled to coincide with the Engine Performance steps.

NOTE: Under no circumstances should the fuel injection pump be replaced until directed to do so by the Engine Performance Pinpoint Test. The only exceptions to this are in the case of Excessive Black Smoke (Symptom Analysis Diagnostic Procedure H) and external leaks.

NOTE: Service each concern detected before going on to the next step. If service corrects the original complaint, it will not be necessary to proceed to the next test step. However, if the complaint is not corrected, continue with the test until the complaint is corrected.

PINPOINT TEST STEPS
The following explanations refer to the basic test steps of the Engine Performance Diagnostic Procedures. They give a brief description of how these problems can affect performance and an understanding of the importance of each test step.

EPC1 External Leakage: Fuel leakage may cause diesel fuel smell or low economy. Oil leakage may cause high oil consumption. An air intake system leak can shorten engine life, especially under dusty conditions. Coolant leakage can result in engine overheating.
EPC2 Accelerator Linkage: If the accelerator linkage is improperly adjusted, the engine cannot reach full rated RPM and top speed and pulling power will be reduced, or curb idle speed will be excessive.
EPC3 Exhaust System Condition: Kinks or dents in the exhaust system can cause high exhaust back pressure. This can result in loss of power and high smoke levels.
EPC4 Turbocharger Boost: If the turbocharger is not functioning correctly it may result in low power, excessive smoke, and poor fuel economy.
EPC5 Wastegate Actuator Condition: If the wastegate actuator is not functioning correctly it could result in an overboost condition (if the wastegate is stuck closed) or poor performance (not reaching desired boost due to wastegate being stuck open).
EPC6 Fuel System Air Leaks: Loose connections can leak air into the fuel. This can result in loss of power and high smoke levels.
EPC7-8 Fuel Quality: Diesel engines need clean fuel, free of air, dirt, and water. Any contamination may result in poor engine performance.
EPC9-12 Fuel System Condition: Kinks in the fuel lines or hoses can block or restrict fuel flow. This can result in loss of power and high smoke levels.

NOTE: The fuel supply system must deliver the proper quantity of fuel with no pressure loss or air leaks in chassis fuel system.

EPC13 Fuel System Return Line Restriction: A restriction in the fuel return line will raise the pressure in the injection pump causing an adverse effect on injection pump timing, resulting in excessive smoke levels or loss of power.
EPC14 Air Cleaner Restriction: A dirty air cleaner may result in low power, excessive smoke and poor fuel economy.
EPC15 Engine Idle Speed: Low engine idle speed may cause stalling or rough running.
EPC16 Injection Timing: Incorrect timing can be responsible for poor fuel economy, rough idling or hard starting and excessive smoke.

NOTE: If the concern is hard starting, follow the procedures for troubleshooting the glow plug system prior to troubleshooting the fuel system.

EPC17 Transfer Pump Pressure: This is the pressure which is available to charge the injection plunger. Low pressure will result in loss of power, and excessive smoke levels.
EPC18 Injection Nozzle Test: The injection nozzles must be removed from the engine for this test. This is a functional test of injection nozzle performance. Incorrect nozzle performance will cause misses, poor fuel economy, loss of power, and excessive smoke.
EPC19 Crankcase Pressure: This test measures the amount of crankcase blow-by. More blow-by will create high pressures. Crankcase pressure readings, plus rate of oil consumption, should be used to evaluate engine mechanical condition.

Pressure Test Kit Hookup:

To perform the Engine Performance Diagnostic Procedure it will be necessary to connect the Pressure Test Kit, Rotunda 014-00761 or equivalent, to the various components as shown in the Pressure Test Kit Hookup image.