Compression
Check engine mechanical condition using a compression gauge, vacuum gauge or engine analyzer capable of performing a relative compression test. If using engine analyzer, see engine analyzer instruction manual for availability and description of relative compression feature.
| WARNING | Because fuel injectors on many models are triggered by ignition switch during cranking mode, DO NOT use ignition switch during compression tests on fuel injected vehicles. Use a remote starter to crank engine to prevent fire hazard or engine's oiling system contamination. |
Exhaust System Backpressure
Before replacing any components, check exhaust system for restrictions. Use a vacuum gauge or a low-pressure (1-5 psi) pressure gauge to check exhaust system.
If using a vacuum gauge, connect gauge to intake manifold vacuum, and start engine. Observe gauge while holding throttle steady at 2000-2500 RPM. If vacuum gauge reading slowly drops after stabilizing, exhaust system may be restricted.
- Check At AIR Pipe
Remove rubber hose at exhaust manifold AIR pipe check valve, and remove check valve. Install pressure gauge to hose and nipple via Propane Enrichment Device (J26911). Nipple should be inserted into exhaust manifold AIR pipe.
- Check At Oxygen Sensor
Remove oxygen sensor. Install backpressure tester in place of oxygen sensor. After test is completed, coat oxygen sensor threads with anti-seize compound before installation.
- Diagnosis
Check exhaust system for collapsed pipe, heat distress and possible internal muffler failure. If none of these conditions exists, check for restricted catalytic converter. Replace as required. Start engine and bring to operating temperature. Increase engine speed to 2000-2500 RPM. Note gauge. Exhaust system is restricted if reading exceeds 1.25 psi (.09 kg/cm 2 ).
Definition
No-start is defined as engine cranks okay but does not start. Engine may fire a few times.
SUMMARY
If faults were not found while performing BASIC DIAGNOSTIC PROCEDURES, proceed to appropriate G - 6.5L TESTS W/ CODES article in the ENGINE PERFORMANCE section below. If no hard codes are found in self-diagnostics, or vehicle does not have a self-diagnostic system, proceed to TESTS W/O CODES - 6.5L DIESEL article in the ENGINE PERFORMANCE section for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent diagnostic procedures.
- «TESTS W/CODES - 6.5L DIESEL»(ref-19760) (for "C" & "K" Series)
- «TESTS W/CODES - 6.5L DIESEL»(ref-19761) (for "G" & "P" Series)
