The air pump on my bronco with a 5.0 always sounded like it was pumping the air out of the system when its hot or cold so I unplugged the vacumn line at the valve right after the pump and now air is flowing through the system,I am familiar with the system that was on my 87 that had a carbed 351 that had one single divertor valve unlike the 88 that has the valve right after the pump and the divertor valve behind the motor. What controls the vacumn to the valve right after the pump as it looks like its getting vacumn all the time,if it wont hurt anything i might leave it as it is since it does not make that annoying sound with the air going through the system and might make it just pump air to the cats all the time.

 

I figured it out and it works basicly the same as my 87 I had years ago,if I disconnect the line at the divertor valve it will shot air back to the cat constantly which I was planning but the solenoid that controls it works so I will let it be for now. It just has that valve that shuts off air flow from the pump so it will stay bypassed so air will constantly be going through the system.

 

The smog pump always pumps air. Where it goes depends on which control solenoid is energized. If it sends air to the wrong place you can get backfiring.

 

There should be a diffuser ( muffler ) on the outlet to cut down on the noise. It should vent most of the time.