Troubleshooting air injection smog pump - Mercedes-Benz Forum

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post #1 of 3 (permalink) Old 08-15-2011, 10:06 AM Thread Starter
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Date registered: Jul 2011
Vehicle: 1990 Mercedes 190E 2.6L
Location: Southern California
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Troubleshooting air injection smog pump

I recently bought a 1990 190e 2.6L, California edition. I need to pass the CA smog check just to get it registered. I went through once but it failed because the check engine light wouldn't come on at all. After replacing the bulb I discovered I had to replace the coolant temperature sensor.

It seemed I was ready to go back and re-take the smog test. I drove the car on the freeway for a while to get it warmed up. Right as I pulled into the lot of the testing center the CEL came on again. This time the code was 11 for the air injection system. It seems to have no impact on the driving or operation. Pretty much just an emissions issue and really only a problem in California... but unfortunately I live in California so I have to deal with it.

I've been all over Google and multiple forums trying to find ways to solve this. One thread said it was probably a vacuum issue in the line from the air injection switchover. I tested that line at several points (at the switchover valve, at the check valve, over on the far side by the air cleaner... and it had 15 psi vacuum pressure at all points.

I looked for obvious cables or tubes disconnected from the air pump but don't see anything. I unplugged and re-plugged that electrical cord (which I assume is getting power) that comes off the pump near the wheel and runs along the inside of the fender and back behind the battery. The connection did not look corroded or anything.

Replacing the smog pump itself would cost about $300 plus a good chunk of my time, and probably some flesh from my knuckles. I see that as the last resort... or a direct move if some test confirms that is the real issue. I'd like to test the easiest and cheapest stuff first. I just don't know what else to test.

I have a MityVac vacuum gauge and a multimeter. I'm new to both tools. I'm wondering if anyone can give me any tips on what to do with either of these tools to check for issues in the air injection system and help me eliminate the engine fault code 11.

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post #2 of 3 (permalink) Old 08-16-2011, 02:59 PM
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Date registered: Apr 2008
Vehicle: 1991 190e 2.6 automatic
Location: toronto
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the smog pump wont affect the emission test results.. when the car is warmed up, the smog pump is not even operational.. i would know because i took my smog pump off my 2.6 and i did emissions last month and passed very good. I used a shorter drive belt from a GMC or something. Anyways, i also do emission testing and we dont check for anything usually so if its anything like in toronto, chances are the guys wont check for a smog pump, nor will they know that this car is supposed to have one. It only works for the first 30 seconds or so, supplying oxygen to the catalytic converter so the cat heats up faster. So once it heats up, it turns off.

I dont know how you can fix it but chances are they wont look at it so i would just take it off.
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post #3 of 3 (permalink) Old 08-16-2011, 03:13 PM Thread Starter
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Location: Southern California
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Yes, I've heard of others taking it off, too... but not in California. Here they have different emissions laws. It is part of the visual inspection to see the pump.

But the real issue for me right now is that whether or not the air injection system has any major effect on the car's operation, it causes the check engine light to go on. The smog testing center will not pass the car if the CEL is on for any reason. I've reset the light and when the car gets warmed up it always comes back on with the same code... and the smog check is done when the car is warm. So I'm forced to fix it.

Unless I can somehow get the computer to ignore the air injection system so it won't trip the light.
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