System Check - Restricted Exhaust System with Carburetor

Fig. 1 Pressure Gauge Connection:

Proper diagnosis for a restricted exhaust system is essential before any components are replaced. The following diagnostic procedure is recommended:

1. Remove the rubber hose at the exhaust manifold A.I.R. pipe check valve. Remove check valve.


2. Connect a fuel pump pressure gauge to a hose and nipple from a Propane Enrichment Device, see Figure 1.


3. Insert the nipple into the exhaust manifold A.I.R. pipe.


4. With the engine at normal operating temperature and running at 2500 RPM, observe the exhaust system backpressure reading on the gauge.

5. If the backpressure exceeds 2-3/4 psi, a restricted exhaust system is indicated.

6. Inspect the entire exhaust system for a collapsed pipe, heat distress, or possible internal muffler failure.

7. If there are no obvious reasons for the excessive backpressure, a restricted catalytic converter should be suspected, and replaced using current recommended procedures.