Go Back   MBClub UK - Bringing together Mercedes Enthusiasts > Technical > Electronics
MBClub supports BEN Official Stickers @mbclubuk


Electronics In-Car-Entertainment (ICE), satellite navigation, lighting and wiring

Reply
 
Thread Tools
Old 09-07-2010, 03:21 PM   #1
New Member
 
650max's Avatar
 
Join Date: Feb 2010
Location: Cumbria
Car: Sprinter 311 LWB Luton
Posts: 17
Secondary air pump question

Hi guys

I've recently replaced the dodgy air pump on my C32 with a replacement off ebay (yes I fitted a new relay as well)

I decided to play with the old one to see what was wrong so took the filter end cap off, lo and behold the impellor spins freely so I connected a 12v power supply to the terminals (used a battery charger), it spins momentarily before the overload in the charger trips with the ammeter off scale (above 5 amps), question is, what current would the pump normally draw in service? I can't find which fuse protects it, is there a chance it's just been a burnt out relay in the 1st place?

cheers

Max
650max is offline   Reply With Quote
Old 09-07-2010, 03:27 PM   #2
Hardcore MB Enthusiast
 
markjay's Avatar
 
Join Date: Jun 2008
Location: London
Car: W203 C180K 2006 / Serviced by Olly PCS (BlackC55) / COMAND NTG2.5 retrofitted by Alfie and Richard
Posts: 9,041
Sorry, not too familiar with the particular setup on Mercs, but.... generally speaking secondary air pupms are meant to reduce emissions while the engine is cold and has not yet reached its normal working temperature.

These pumps can become noisy with time and many owners chose to simply disconnect them - MOTs are carries-out at normal engine running temperature anyway so the emissions test will not be affected by the disconnection of the secondary air pump.

Not sure if this info helps though....
markjay is offline   Reply With Quote
The Following User Says Thank You to markjay For This Useful Post:
650max (10-07-2010)
Sponsored Links
Old 09-07-2010, 03:56 PM   #3
Hardcore MB Enthusiast
 
Swozza's Avatar
 
Join Date: Aug 2009
Location: Sheffield
Car: C32 AMG
Posts: 376
In my case it was the relay that burn the pump out. How do I know this, because the mistake of not replacing the relay was made. I'd say the pump burnt out after 100 miles.
Swozza is offline   Reply With Quote
The Following User Says Thank You to Swozza For This Useful Post:
650max (10-07-2010)
Old 09-07-2010, 04:03 PM   #4
Hardcore MB Enthusiast
 
Alps's Avatar
 
Join Date: Nov 2002
Location: London\Essex
Car: C36 AMG 1997 (SOLD), E55 2004 Silver
Posts: 5,838
disconnection would cause the engine management light to come on!

mine had a burnt out relay, was replaced and all is still fine 8 mnths later
Alps is offline   Reply With Quote
The Following User Says Thank You to Alps For This Useful Post:
650max (10-07-2010)
Old 11-07-2010, 02:06 PM   #5
New Member
Threadstarter
 
650max's Avatar
 
Join Date: Feb 2010
Location: Cumbria
Car: Sprinter 311 LWB Luton
Posts: 17
Bump
650max is offline   Reply With Quote
Old 11-07-2010, 02:46 PM   #6
Authorised Forum Sponsor
 
jaymanek's Avatar
 
Join Date: Nov 2002
Location: Nuneaton Warwickshire
Car: Lots of Mercedes!
Posts: 15,504
Yes its normally the relay that causes the pump to fail.. Did you change the relay? I dont think there is a fuse, just the relay.
jaymanek is offline   Reply With Quote
Old 12-07-2010, 05:06 PM   #7
Hardcore MB Enthusiast
 
misfire84's Avatar
 
Join Date: Jan 2010
Location: Banbury
Car: w204 250 GDI estate and hers c270cdi
Posts: 105
the engine managment light doesl not come on as I have had the air pump disconected for 4 months now and no engine check light on , the Relay is still conected the valves blanked off . next job is to put a blanking plate on the head so the vacume valves can be removed totaly so tidy up it up .
misfire84 is offline   Reply With Quote
Old 28-03-2011, 03:58 PM   #8
New Member
Threadstarter
 
650max's Avatar
 
Join Date: Feb 2010
Location: Cumbria
Car: Sprinter 311 LWB Luton
Posts: 17
I thought I'd investigate things further as I've now got 2 pumps, neither of which is working right? .... Wrong!

Put a motorbike battery across the pump terminals and both run fine, connect an ammeter in and they both show as drawing 0.5 amps, not excessive at all.

With the engine cold and the pump removed, start engine and I have 14.4 volts across the pump wires and the solenoids/vacuum valves are obviously open because of a little blowback through the hose, very quickly connect the wires to the pump terminals and..... nothing and about 15~20 seconds later, the tickover drops and the vacuum valves close so obviously the ECU has decided it doesn't need the pump any more, at this point the voltage across the pump wires drops to about 8 volts.

So now I'm confused, with a 12 volt battery connected directly, the pump runs fine but won't run at all with 14.4 volts supplied by the pump wiring, can this be down to the relay? Any suggestions?

cheers

Max


P.S.

If your pump is noisy, this will probably be down to the bearings in the motor, they can be replaced if you're careful, size is 608RS, I've just got a pack of 10 off ebay for 3.50 inc postage, C2 grade.
650max is offline   Reply With Quote
Old 28-03-2011, 06:04 PM   #9
New Member
Threadstarter
 
650max's Avatar
 
Join Date: Feb 2010
Location: Cumbria
Car: Sprinter 311 LWB Luton
Posts: 17
Quick edit

Tried a different, brand new relay, the voltage at the wires is now 12.5 which drops to as near zero as makes no difference once the cold start system shuts down, still can't get the pump to run so my only idea is the startup current for the pump motor must be too high?
650max is offline   Reply With Quote
Old 28-03-2011, 08:56 PM   #10
Hardcore MB Enthusiast
 
Justin1600's Avatar
 
Join Date: Dec 2010
Car: C43 AMG
Posts: 1,901
The most common problem with this system after the relay going wrong, is the air pump switch over valve. Change this and then re-try it mate, they are only about 19 quid
Justin1600 is offline   Reply With Quote
Old 28-03-2011, 09:42 PM   #11
New Member
Threadstarter
 
650max's Avatar
 
Join Date: Feb 2010
Location: Cumbria
Car: Sprinter 311 LWB Luton
Posts: 17
Cheers Justin

Can you tell me whereabouts this valve lives or what it looks like?

Max
650max is offline   Reply With Quote
Old 28-03-2011, 09:55 PM   #12
Hardcore MB Enthusiast
 
Justin1600's Avatar
 
Join Date: Dec 2010
Car: C43 AMG
Posts: 1,901
Quote:
Originally Posted by 650max View Post
Cheers Justin

Can you tell me whereabouts this valve lives or what it looks like?

Max

It is probably at the front of the egine, it will have two vacuum pipes going to the top of it and a multiplug. Black in colour
Justin1600 is offline   Reply With Quote
The Following User Says Thank You to Justin1600 For This Useful Post:
650max (28-03-2011)
Reply

Tags
air, pump, question, secondary


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools



All times are GMT +1. The time now is 01:15 AM.


MB club UK is A Mercedes Enthusiast club run by enthusiasts for enthusiasts, MBClub UK is in no way affiliated with Mercedes-Benz, DaimlerChrysler or any of their respective trademarks. The posted views of our members are in no way the views of MBClub.co.uk or its owners.
Find us on Google+