Thread: DMTL pump bad
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      12-14-2010, 09:24 PM   #11
330icanadian
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Drives: 2006 330i
Join Date: Mar 2009
Location: Ontario - Canada

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DMTL Pump Repair

2006 330i

After overfilling the gas tank once, the check-engine-light came on within a day or two. The OBD code reader led me to the DMTL pump, which I think is a vacuum pump that sucks the fumes from the top of the gas tank near the filler cap. With the help of the diagram earlier on this thread, I found it and removed it.

Partial disassembly (unsprung the 6 or so plastic clips around the plastic housing) revealed a small 12V DC motor. Applying 12V to the motor terminals resulted in turning the motor, but the action was not smooth. I was able to get it apart further, eventually taking apart the tiny vane pump - a circular rotor with 4 sliding inserts, all made of black plastic. I lightly lubed the rotating parts with some motor oil, and reassembled. Testing it with 12V DC gave a better action and sound. I then reinstalled to the car, reset the OBD codes with the code reader/resetter and it's been fault free for the last week or so!

My guess is that when I overfilled the gas tank, liquid gasoline was ingested by the pump, which would have had the effect of washing away any lubricant from the internal surfaces of the vacuum pump parts, causing it to run slowly or seize once it dried. Will let you know if the lube job holds or not!

Jan.13.2011. Update: Still no check engine light, no faults, for a month now.

June.29.2011 Update: Kept throwing P1447 codes for last few months, so bought a new replacement DMTL pump online, installed it today, reset OBD. Fingers crossed.

Last edited by 330icanadian; 06-29-2011 at 08:39 PM. Reason: update 13-Jan-2011
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