Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   PeachParts Mercedes-Benz Forum > Mercedes-Benz Tech Information and Support > Tech Help

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 03-30-2006, 03:05 PM
Registered User
 
Join Date: Jun 2001
Posts: 259
Is it safe to take a voltage reading at the fuel pumps?

On a 560sl?

Thanks.

JB


Last edited by JBoggs; 03-30-2006 at 09:45 PM.
Reply With Quote
  #2  
Old 03-30-2006, 09:21 PM
Super Moderator
 
Join Date: Apr 2000
Location: Falls Church, VA
Posts: 5,316
??????????

If you mean "same" - same as what?

If you mean "sane" - yes. You should get at least 11.5 volts and 6-10 amps.
__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
Reply With Quote
  #3  
Old 03-30-2006, 09:43 PM
Registered User
 
Join Date: Jun 2001
Posts: 259
Crap, meant to say safe....not same.

Having no start probs, think it's fuel relay related.

Thanks.

JB
Reply With Quote
  #4  
Old 03-31-2006, 11:22 AM
Mike Murrell's Avatar
Registered User
 
Join Date: Feb 2000
Posts: 2,574
Jboggs:

What yr. is your 560SL?

If it's a 1900 or 1991, it may be equipped with what's called a MAS. Silver box on drivers side near fire wall. It has a knob on top that you loosen counter clockwise. Once loosened, the whole unit comes out.

Ports 1 & 2 are jumpered to power fuel pump(s). These 2 ports are what's used by the fuel pump relay. The FPR is incorporated into the MAS on cars equipped with such.

If you jumper 1 & 2 and the car starts, the fuel pump relay within the MAS is bad and the MAS has to be replaced. If not, your pump(s) may be bad. The MAS is $500 + at the dealer.

I once read here that the MAS can be opened and soldered. I'm not an electrics expert, but would wonder just how a diyer would go about opening this unit?

Be careful when you jumper 1 & 2. One or both is wired hot and if you don't hit them both just right with the jumper wire, you'll get a spark.

Understand that you really cannot operate the car like this. Jumpering 1 & 2 will prove if the FPR is functional or not. If the car starts and runs jumpered, you'll get a Check Engine light. This will reset itself once the MAS is reinstalled.

MAS units that contain Fuel Pump Relay

If your MB does not have a MAS, locate the fuel pump relay and jumper the correct pins. I seem to recall they are 30 & 87, but a SEARCH would verify this. If you have a faulty "independent" FPR, your wallet won't get hit as hard.

If the weather holds up, I'll be replacing my MBs fuel pump this weekend.
__________________
Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"

Last edited by Mike Murrell; 03-31-2006 at 12:05 PM.
Reply With Quote
  #5  
Old 03-31-2006, 03:08 PM
Registered User
 
Join Date: Jun 2001
Posts: 259
86 560sl.

The fuel pump relay on mine is behind the glove box I believe. I'm gonna have to jiggle it some over the weekend or just replace the stupid thing.

Funny thing, been having the no starts for several months off and on, but a week or so ago, the alarm started going off by itself. I pulled the connections to the alarm which is really close to the relay. I have checked it twice to make sure I didn't knock it loose but somehow the two must be related. I hope it's just a relay or a dirty connection and now a computer related problem.


JB
Reply With Quote
  #6  
Old 03-31-2006, 03:26 PM
Mike Murrell's Avatar
Registered User
 
Join Date: Feb 2000
Posts: 2,574
JB:

I read in an old post here that MB factory alarm systems play no part in keeping the vehicle from starting. Fctory alarm merely provideds an audible alert.

If that's true, you could rule out the factory alarm as the culprit.

Not sure what type of alarm you have.
__________________
Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"

Last edited by Mike Murrell; 03-31-2006 at 04:29 PM.
Reply With Quote
  #7  
Old 03-31-2006, 05:31 PM
Registered User
 
Join Date: Jun 2001
Posts: 259
Yes, I'm aware...

but the possiblity remains that I knocked something loose or bent a relay or ? I was suprised how easy it was to defeat the alarm-a thiefs dream.

Thanks for the reply.

JB
Reply With Quote
  #8  
Old 04-05-2006, 05:20 PM
Senior Member
 
Join Date: Jun 2001
Location: Northern Calif. (Fairfield Area)
Posts: 2,225
Quote:
Originally Posted by JBoggs
but the possiblity remains that I knocked something loose or bent a relay or ? I was suprised how easy it was to defeat the alarm-a thiefs dream.

Thanks for the reply.

JB
Not really. Eliminating the alarm is the easy part. Breaking that case hardened ignition tumbler is the challenge. I'm suspecting you have one or both fuel pumps going out. You can check current flow and wave form to each pump. A scratchy waveform means you have a failing pump. A clean waveform means you might have a failing pump. If you have a pump that has been drawing too much current, you may as well replace the relay too.
__________________
Auto Zentral Ltd.
Reply With Quote
  #9  
Old 04-05-2006, 08:25 PM
Mike Murrell's Avatar
Registered User
 
Join Date: Feb 2000
Posts: 2,574
Earlier this evening I posted some incorrect information - had my head up the wrong place. I suggested pulling a fuse from the main box and hooking up an amp meter in series at that spot.

There is no such "fuse". Looking back thru the archives, one would pull the fuel pump relay and do the amp meter hook up there to read current draw.

In an old post, M.B.Doc indicated that single pump systems should draw less than 8 amps; dual pump systems should draw 6 - 7.5 amps.

Fuel pump or Fuel p relay? Doc,Benzmac,SteveB

__________________
Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"

Last edited by Mike Murrell; 04-05-2006 at 11:50 PM.
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On




All times are GMT -4. The time now is 06:19 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page