Smog Pump


Not all engines are equipped with an air injection system, only those that need them to meet emissions standards have them. Therefore, air injection systems are vital to proper emissions on engines equipped with them. Each system has its own test procedure; always follow the manufacturer's recommendations for testing.

There are three basic designs of air injection systems. One type is an air injection system with an air pump, distribution manifold, check valve, diverter valve, hoses to the intake and exhaust, and a vacuum signal line. The other two systems don't use an air pump.

The first step in diagnosing a secondary air injection system is to check all vacuum hoses and electrical connections in the system. Many AIR system pumps have a centrifugal filter behind the pulley. Air flows through this filter into the pump, and the filter keeps dirt out of the pump. The pulley and filter are bolted to the pump shaft, and these two components are serviced separately. The pump assembly is usually not serviced.


Listen to see if the smog pump is making noises. It is important to try to determine the location of noises before disassembling the engine. There have been cases where engines have been disassembled, inspected, and rebuilt, but when reinstalled in the car still had the same problem. Pinpointing the origin of the noise might have resulted in more careful scrutiny of the offending part while the engine was apart. Noises are often transmitted from their origins to other locations, and can be difficult to isolate.

Listening through a stethoscope, or listening at the end of a large screwdriver, a piece of hose, or a long wooden dowel are some of the ways to help pinpoint noises.

Accessories often cause noises that can be mistaken for other problems. Be sure to check smog pump carefully.

Use the following general procedures to inspect the air pump:

  • Check the for the correct tension on the air injector reactor pump belt. This can be done using a belt tension checker.
  • There should be no air leaks in the air system components. Look for air leaks in the hoses and the air injection tubes on the exhaust manifold. If there are any leaks, replace the components as necessary.
  • Check the mounting bolts for looseness and to see if the pump is aligned correctly.
  • After removing the belt, check for a seized air pump. Replace if necessary.
  • Check for loose air pump hoses.
  • Check for a defective pressure relief valve.
  • Inspect the check valves for air flow in only one direction. Replace if necessary.