ASPIRATOR SYSTEM OP TEST INFORMATION

Subject: 1981 "B" CARS EQUIPPED WITH A 3.8L (LD5) ENGINE - ASPI- RATOR SYSTEM OPERATION AND TESTING

Aspirator, P/N 25030978, used in 1981 "B" 3.8L (LD5) air cleaner assembly number 25040815, provides a vacuum signal to the EGR valve by using the divert air from the A.I.R. control valve under low engine vacuum conditions. The aspirator contains a back pressure valve which creates sufficient back pressure to operate an internal Venturi system that creates the vacuum signal. Divert air entering port "A" (see Figure 1) is restricted from discharging into the air cleaner by the valve and spring in the aspirator. The pressure developed in the line feeding port "A" also flows through a Venturi system within the aspirator, when port "C" is open, creating a vacuum at port "B".

To perform a basic functional check on the aspirator assembly:

1. Disconnect hose from port "C" and temporarily plug hose (leave port "C" open to atmosphere).

2. Attach a vacuum gage to port "B".

3. Run engine until A.I.R. valve diverts air to the air cleaner (this air flow can be felt at the aspirator outlet inside the air cleaner).

4. While running engine at 1500 rpm (in park), vacuum gage should read greater than three (3) inches Hg.

If aspirator will not develop greater than three (3) inches Hg. check for split or damaged air lines. If no leaks are found, install new aspirator assembly and repeat above procedure. If new aspirator will not develop greater than three (3) inches Hg. check for malfunctioning A.I.R. valve or A.I.R. pump.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.