Took the C280 to shop for an error code. Code came up as a bad smog pump or secondary air intake pump going bad. They wanted to charge me 1400 bucks to replace it. Trying to do it myself. I can't find any good sources that shows me where the pump is actually located. Does anyone have any ideas where this is at on my motor?

Thanks.

Please be sure to post the solution you find to help others in the future.

Look below the alternator, there is a similarly sized black round item that is the air pump. For 96 it should be electric powered, older ones were belt driven.

There is more to the system besides the air pump. At the front top of engine ( under the black plastic cover that has a MB star on it) there is a vacuum solenoid valve. Check this and the tubing running to and from. The tube that runs under the coil cover eventually leads to the air diverter valve. This diverter valve lives between the two exhaust manifolds.

I've had the vacuum solenoid to diverter valve line get caught under the coil cover and crushed so have a look there as well.

Also, in the underhood black box ( base of windshield, passenger side ) there is a relay / 40 amp fuse for the pump, check these parts.

$ 1,400 is way big for this job. A used pump would be the way to go if it is bad. Try car-part.com , this is a nation wide salvage yard inventory search.

97 SL320 your correct sir!!! Shortly after posting my question ,I followed a vacuum line which ducked underneath the alternator. I went underneath the car, removed the protective cover and found it. It appears to be attached by three (possibly 10mm) bolts. It is located on the front passenger side of the motor underneath the alternator and it is electric powered not belt driven.

As for the relay, I opened the box but I spotted at least eight (40) amp fuses. I wanted to replace this first before I buy a 400 dollar part. Problem is, not sure which fuse belongs to the pump. Do you have any ideas?

CARQUEST had the cheapest refurbished air intake (smog pump). Price is 377. More to follow ill keep this updated in the next week.

Thanks again for you help.

spot 28 frt fuse box 40 amp fuse

You can look through the fuse plastic and see if the link is burned or use a test light / ohm meter.

Don't replace the pump until you have unplugged it and checked for power at the pump just after a cold start. ( Be sure to keep test wires away from the fan belt )

You can also apply power to the pump and see if it spins. You will get a pretty big spark when attaching a wire as it draws lots of power. Polarity matters for rotation of direction, I don't have a wiring diagram handy to check that out.

Long story short I purchased a new Smog Pump and had to change it out. I changed the relay but it did not work, a few weeks later the error code came back. I changed the pump but I am still having rough start problems. On some starts the RPM's drop very much almost as if the car wants to die on me. Once it warms it runs like a champ though. Anyone have this problem? I looked online and it seems I may have a volt regulator problem, has anyone had this or has any info about this?

Did you clean the throttle body? Frequently oil sludge builds up between the blade and body reducing air flow. Use cleaner spray, a screw driver to prop the blade open and another with a rag wrapped around it to scrub.

if you are in a tailpipe test,you can buy used pumps on EBAY,saw one today for a $100.Also examine your large hoses running to air pump,and hoses running to intake manifold.They get hard,and break,also fall off.If your not in a emissions state just block off the hoses.Also check yourhard plastic vaccum lines they crack.

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