C 1500 Truck 2WD V8-350 5.7L VIN K TBI (1995)
Catalytic Converter: Testing and Inspection
Exhaust System Check
RESTRICTED EXHAUST TEST
Proper diagnosis for a restricted exhaust system is essential before any components are replaced. The following procedure(s) may be used for
diagnosis:
CHECK AT AIR PIPE
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Remove the rubber hose at the exhaust manifold AIR pipe check valve and remove check valve.
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Connect a fuel pump pressure gauge to a hose and nipple from a Propane Enrichment Device.
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Insert the nipple into the exhaust manifold AIR pipe.
CHECK AT 02 SENSOR
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Carefully remove O2 sensor.
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Install Exhaust Backpressure Tester in place of 02 sensor.
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After completing the diagnosis described below, be sure to coat threads of 02 sensor with anti-seize compound prior to re-installation.
DIAGNOSIS
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With the engine idling at normal operating temperature, in park or neutral, observe the exhaust system backpressure reading on the gauge. The
reading should not exceed 1.25 psi or 8.6 kPa. Increase engine speed to 2000 rpm and observe gauge. The reading should not exceed 3 psi or 20.7
kPa.
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If the backpressure exceeds the given specifications, a restricted exhaust system is indicated.
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Inspect the entire exhaust system for a collapsed pipe, heat distress, or possible internal muffler failure.
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If there are no obvious reasons for the excessive backpressure, a restricted catalytic converter should be suspected, and replaced.
WITH VACUUM GAUGE
Engine at normal operating temperature:
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Connect a vacuum gauge to any convenient vacuum port on intake manifold.
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Run engine at 1000 rpm and record vacuum reading.
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Increase rpm slowly to 2500 rpm. Note vacuum reading at a steady 2500 rpm
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If vacuum at 2500 rpm decreases more than 3" Hg, from reading at 1000 rpm, the exhaust system should be inspected for restrictions
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Disconnect exhaust pipe from engine and repeat Step 2 & 3. If vacuum still drops more than 3" Hg, with exhaust disconnected, check for exhaust
manifold restriction and valve timing.
