How does the smog pump work?

The pump constantly pumps. The valve behind the pump directs air to the heads during cold startup and to the cats once the car is warmed up. If you still have cats then keep the smog pump tube from teh pump to the cats, without it they go bad.

FWIW it is NOT a smog pump. It is an air pump or as Ford calls it a Thermactor. It does not pump smog unless you live in LA or somewhere like that.

BlackFox5.0 said:

I was told by a friend of mine that the pump just reduces tail pipe emissions. Which does sound reasonable. I've seen cats with the tube in the middle of the cat. What good is that to the front half of the cat? There are alot of theories out there to what it does, all I know is it helps lower my emissions.

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Correct it reinserts exhaust gas as an inert gas therefore reducing combustion temp and NOx. WIth the air hose in the middle of the cat is a dual stage cat (reduction and oxidation) and the other is a single stage.

giddyup306 said:

Correct it reinserts exhaust gas as an inert gas therefore reducing combustion temp and NOx. WIth the air hose in the middle of the cat is a dual stage cat (reduction and oxidation) and the other is a single stage.

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I think you are describing the EGR system to him. The thermactor system is different. It inserts oxygen into the cats to help in the reaction. And when it inserts air into the heads it is to make the exhaust more oxygen rich and trick the o2 sensors into richening up the air/fuel ratio during warm up.

nito88stang said:

I think you are describing the EGR system to him. The thermactor system is different. It inserts oxygen into the cats to help in the reaction. And when it inserts air into the heads it is to make the exhaust more oxygen rich and trick the o2 sensors into richening up the air/fuel ratio during warm up.

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Correct. I thought he was tallking about the emissions systems as a whole.

The smog pump has two vacuum operated valves. The first valve either dumps the pump output to the open air or directs it to the next valve. The smog pump dumps its output at full throttle to save horsepower. The second valve directs the air to either the passages in the heads or to the tube that runs to the cat converters. Both the tube for the head and the tube going to the cat converters have one way check valves to prevent the hot exhaust gas from backing up into the tube and the control valves.

Here are some of the codes generated by faulty parts in the smog pump system and their fixes...

Codes 94 & 44 - Check vacuum lines for leaks, & cracks. Disconnect the big hose from smog pump: with the engine running you should feel air output. Reconnect the smog pump hose & apply vacuum to the first vacuum controlled valve: Its purpose is to either dump the pump's output to the atmosphere or pass it to the next valve. The next vacuum controlled valve directs the air to either the cylinder heads when the engine is cold or to the catalytic converter when the engine is warm. Disconnect the big hoses from the back side of the vacuum controlled valve and start the engine. Apply vacuum to the valve and see if the airflow changes from one hose to the next.

The two electrical controlled vacuum valves mounted on the rear of the passenger side wheelwell turn the vacuum on & off under computer control. Check to see that both valves have +12 volts on the red wire. Then ground the white/red wire and the first solenoid should open and pass vacuum. Do the same thing to the light green/black wire on the second solenoid and it should open and pass vacuum.

Remember that the computer does not source power for any actuator or relay, but provides the ground necessary to complete the circuit. That means one side of the circuit will always be hot, and the other side will go to ground or below 1 volt as the computer switches on that circuit.

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host)

http://www.veryuseful.com/mustang/t...inks-ign-ac.gif

http://www.veryuseful.com/mustang/t...91eecPinout.gif

Code 81 – Secondary Air Injection Diverter Solenoid failure AM2. The secondary air diverter valve (rear vacuum operated valve) isn’t working on the Thermactor Air System (smog pump). Look for broken or missing vacuum lines on the solenoid valve to the diverter valve. The solenoid valve is located on the back side of the passenger side wheel well. Check the solenoid valve for +12 volts at the Red wire and look for the Lt Green/Black wire to switch from +12 volts to 1 volt or less. The computer controls the valve by providing a ground path on the LT Green/Black wire for the solenoid valve.

See http://www.veryuseful.com/mustang/t...ng5.0Vacuum.gif for help on the vacuum line plumbing.


Code 82 – Secondary Air Injection Diverter Solenoid failure AM1. The dump valve air diverter valve (front vacuum operated valve) isn’t working on the Thermactor Air System (smog pump). Look for broken or missing vacuum lines on the solenoid valve to the diverter valve Check the solenoid valve for +12 volts at the Red wire and look for the Red/White wire to switch from +12 volts to 1 volt or less. The computer controls the valve by providing a ground path on the Red/White wire for the solenoid valve.

nito88stang said:

And when it inserts air into the heads it is to make the exhaust more oxygen rich and trick the o2 sensors into richening up the air/fuel ratio during warm up.

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can you please explain further? i did not think the O2's were used during warm up (open loop). please eliminate my (now, although perpetual. LOL) confusion.

Another question related to this thread...

My car does not have cats. Should the line that goes from the check valve down to where the cats used to be be capped or allowed to vent? Thanks!