QuestionQUESTION: Bought a used air pump for a 2000 BMW 323CI series. Is there a way that I can check it to see if it works before I put it on. There is a two prong plug on the bottom for the air pump motor.
ANSWER: I am not that familiar with late-model BMWs, but I didn't think that they had air pumps. Now, when you say air pump to a mechanic or a parts guy, he's going to assume that you mean an A.I.R. pump, commonly referred to as a smog pump. A German car that new shouldn't need a smog pump, in fact I don't know if BMW ever used them, even on U.S. spec models. So, I'm wondering if you are referring to the air conditioning compressor, which you can't check without installing it and charging the system. If it's something else, let me know and I'll try to figure it out.
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QUESTION: That pump has to do with the emissions. The manual says it is the secondary air injection pump. I don't know how to check it electrically to see if it works. The manual doesn't tell you how to check it. It is a used part. Hope this may help you better. Thanks.
Answer OK, that surprises me. Well, not really 'cause those engineers at BMW really hate simple systems. Assuming that this is not a belt-driven pump, then two connections means placing a voltage across those pins gets the motor working. I would take a jumper wire from the positive and the negative post of a 12V battery (use a lantern battery if you have one laying around, they are fairly common, or the battery in the car if that's all you've got). Hook the positive to one side and briefly touch the negative to the other, while keeping the pump from touching the car (hold it in a rag in your hand, or, better yet, have a friend hold it for you). Remember, just complete the connection for a second or less. If the pump works, you will hear it pump while the connection is made.
If the pump is belt-driven, you can turn the pulley to make sure the innards aren't seized up, but then you'll have to install it to see if it does what it's supposed to do. If the pump is belt-driven, then that plug is some sort of sensor or switch and you shouldn't fool with it.
Now, I will say that, back in the day, we always used to take the air-injection pumps off of the cars when they failed and throw them away. Nowadays that probably isn't a good idea, since the pump doesn't harm the performance of the engine and does help it burn cleaner.
