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Straight answer (archive)
[ Follow Ups ] [ 7-series (E23) Message Board ] [ Msg. Board FAQ ]
Posted by Bruce on December 05, 2000 at 17:43:43:

In Reply to: Re: Dave... posted by Aaron on December 05, 2000 at 17:21:06:

Youre saying that your pumps run without cranking the car?


Yes, I think its the fuel pump, I may be wrong, it may be some sort of vacume pump, but it starts when the the key is in the run position. Should I have this looked at. No one has ever mentioned it as a problem. Thanks - Dave


Your HVAC vacuum pump will also operate, prior to starting, in the run position. Where is the "noise" coming from? Under the hood? If so, put your hand on the vacuum pump. You will feel it operate.


That might be it, the 'noise' comes from under the hood near the p/s pump. sorry about the confusion. On that note, however, A 745 owner told me to put the car in run for a few seconds before starting to let the fuel pump run, is this bunk?
Thanks
Dave


I think it might be -- i cant seem to get a straight answer to save my life!

Pump near PS pump is the HVAC vacuum pump. It will run prior to start to provide vacuum for the vent motors prior to the engine supplied vacuum. I have a 745 and I do not let the fuel pump run prior to starting. Nor does the owner's manual call for this. The vacuum pump will burn out if allowed to run continously. It should cycle and is intended to be supplemental to engine vacuum.


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