Unidentified electric motor sound

[Socrates]

Not sure where to place this query as I really have no idea what is going on. I have a 1990 R129 300SL. When I get in the car there is a sound like some kind of small electric motor, that pulses and continues until I start the car. Is it the fuel pump? should I hear it? Does anyone know what this is?

 

[television]

Not sure where to place this query as I really have no idea what is going on. I have a 1990 R129 300SL. When I get in the car there is a sound like some kind of small electric motor, that pulses and continues until I start the car. Is it the fuel pump? should I hear it? Does anyone know what this is?

The only one that I can think of would be the vacuam pump, thats the only thing that is live without the Key being turned.

What do you think Stats

malcolm

 

[Socrates]

Thanks,
what does the vacuum pump do? .... scuse my ignorance!

 

[Pipemaster]

The vaccum pump operates all the locks inlcuding the petrol filler cap and the boot lock. You may find that although the doors unlock OK the fuel filler cap does so later and the boot lock even later still. I have a 320 thats later than yours and it does the same on mine at the moment ( its going into my specialist to look at along with a few other bits and bobs next week) I have been told that either a component or one of the pipes is leaking and causing the small motor to work overtime in trying to create a vaccum to unlock the boot. its thant motor I - and I think you - can hear. It's located under the rear shelf or seat area.

Hope this helps

 

[television]

There you have the perfect answer from Pipemaster.

malcolm

 

[Socrates]

Well, it looks very much as though that's the thing, since I've had a little trouble persuading the driver door to lock. It's a bit difficult to test, of course, 'cause it sets the alarm of if you try to open it after you've locked it - I'll have to find a car park or something where I'm not likely to be accused of trying to steal it!
Thanks a lot chaps!

 

[television]

Just on the off chance, the last few cars with the same problem, the fault was on the boot lock where the pipe was lose.

malcolm

 

[Pipemaster]

this was ther post on another thread

Just sorted a vacuum problem, pump running for ages when Central Locking used, and yes it was the boot lock!. However all I did to ID the source was to remove a pipe from the pump block end with finger and use Central locking. When you find a pipe that when blocked with finger lets pump run for a second or two you have the culprit. Located boot central lock behind a cover plate next to the lock and found the air/vacuum pipe had worked a fraction loose, could hear it sucking and blowing when locks activated. Couple of twists of the air pipe, seal restored and all's well. Hope yours is as simple.

Hope it helps