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 > Vintage Mercedes Forum

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 11-09-2009, 10:51 PM
sjefke's Avatar
Registered User
 
Join Date: May 2006
Location: Atlanta, GA
Posts: 591
Starter(s) or wiring problem? - 280se 3.5 cpe

Well, I cheered to soon. I have had a problem with a non-engaging started on my 3.5 coupe (see my Bosch SR59X post). Bought a remanufactured starter on ebay, installed it and thought I had it fixed. Now I have the same problem again but with the new starter. Starter solenoid clicks but starter does not engage until after 5-6 tries (not consistent - sometimes it starts on first try, sometimes it takes longer). Once it engages, starter runs at normal speed.

I had the battery checked this afternoon and it was good: it had 600+ CCA in it (rated at 700 new).

Starter spins if solenoid is bypassed.

Cables, terminals have been cleaned (several times now).

I measure 12+V on the main starter terminal (thick cable) so that looks good.

BUT, I measure only 9.3 V on one of the starter solenoid terminals (the one with the thick screw closest to the main terminal). I also measure 9.3 V on the same wire where it is connected to the connector block behind the alternator.

Is that 9.3V normal?? Shouldn't that be 12 V? Where does that wire get its voltage from?

So, do I have 2 bad starters or a circuit problem in my car?

Thanks,

Bert (who is thoroughly puzzled right now and suspects D-jet electrical Gremlins have taken over his car)

__________________
'70 111 280SE/c 3.5 (4 spd manual) - sold
'63 MGB
'73 MGBGT V8
Reply With Quote
  #2  
Old 11-10-2009, 01:03 PM
Super Moderator
 
Join Date: Apr 2000
Location: Falls Church, VA
Posts: 5,318
I think you are talking about the wire from the start side of the ignition switch to the solenoid. You need enough power on that circuit so that the solenoid can pull the main contact back to get power to the starter motor from the large cable. 9.3 volts is marginal which is why it probably works some of the time.

I would guess you have a bad connection between the switch and the starter or a break or corrosion in the wire.
__________________
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 11-10-2009, 06:48 PM
sjefke's Avatar
Registered User
 
Join Date: May 2006
Location: Atlanta, GA
Posts: 591
I suspect as well I need 12 V instead of 9.3... According to the wire diagram for my car, the solenoid is grounded over the ignition switch. As soon as you put the switch on position 1 (ignition), the solenoid gets its + Voltage. The + wire to the solenoid apparently comes from the 0.4 Ohm series resistor near the coil (at least according to the diagram). I am planning to chase that wire, but I just want to make sure that I should indeed get 12 V from that point, and not 9.3V.

I will first try a direct +12V wire connection from the solenoid to the battery just to see whether that makes a difference. That should allow me to test whether the ground circuit to the key is fine.

Also, all wire diagrams list the P/N starter fail safe switch in between the key and the solenoid ground terminal, but I have a manual. I assume it is not in the car, but wonder wether there is yet another connector under the car that could have corroded.

Thanks,

Bert
__________________
'70 111 280SE/c 3.5 (4 spd manual) - sold
'63 MGB
'73 MGBGT V8
Reply With Quote
  #4  
Old 11-10-2009, 08:49 PM
Super Moderator
 
Join Date: Apr 2000
Location: Falls Church, VA
Posts: 5,318
Usually, there are two terminals on the solenoid. One takes the 12V from the Start position of the ignition switch. It should be labeled "50." It looks like the other one "16" goes to the switching unit via the terminal on the resistor and provides 12V when the starter is cranking, the purpose being a hotter spark when starting. When you release the key, the flow the the switching unit goes back through the resistor.
__________________
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
  #5  
Old 11-10-2009, 10:01 PM
cth350's Avatar
Registered User
 
Join Date: Dec 2000
Location: Long Island, NY
Posts: 4,354
Your starter shouldn't be drawing current through the resistor. That wire should be bypassing the resistor to supply current to the ignition.

If you disconnect that lead, does the starter completely fail? If so, one of your other wires has gone south.

Does the neutrall safety switch work as expected?

Thx -CTH
Reply With Quote
  #6  
Old 11-11-2009, 12:08 AM
sjefke's Avatar
Registered User
 
Join Date: May 2006
Location: Atlanta, GA
Posts: 591
Hmm, still puzzled. So, I should see +12V on terminal 50 if I put the key in start position, but nothing when the key is not in start. So the way to hotwire the starter is to put 12V from the battery to terminal 50, correct?

Chuck, if I understand you correctly, terminal 16 should also have no voltage, unless the starter is cranking.

So, why do I have 9.3V on one of the terminals when key is in ignition position? Is that terminal 16 that gets a + voltage from the same wire as the ignition switiching unit after the 4 ohm resistor?

Unfortunately I am out of town and cannot take a look at whether the terminals are labeled. It also does not help that color codes on wires are all violet and red/violet... I do know that one has a larger diameter screw than the other. Which one is 50 and which one is 16?

I don't have a neutral switch because I have a manual transmission, so one less thing to worry about.

Thanks,

Bert
__________________
'70 111 280SE/c 3.5 (4 spd manual) - sold
'63 MGB
'73 MGBGT V8
Reply With Quote
  #7  
Old 11-12-2009, 09:56 PM
sjefke's Avatar
Registered User
 
Join Date: May 2006
Location: Atlanta, GA
Posts: 591
It's the wiring

Made it home today and with the info from Chuck bridged a wire directly from the battery + to the 0 V terminal on the 3 screw terminal behind the alternator where the starter wires connect. Guess what: starter engaged. Kept tapping the wire on the + terminal of the battery and every time, starter engaged.

I had my son start the car while I measured voltage on the terminal, and it shows 9ish Volts. When it did start like that, it had a 10V reading.

Bottom line: starter good, voltage on wire bad.

I know now how to start my car in a pinch, but now I need to start tracing the bad contact/circuitry issue. My first suspect is a bad fuse connection given that I have a low voltage on ignition as well as starter terminals(50 and 16 on the starter). Second suspect may be the ignition key switch, given that I also have electrical problems with my fuel pump relay and ECU. I have a suspicion that they are all related so I need to find the common "ground" or connector/contact.

Thanks,

Bert
__________________
'70 111 280SE/c 3.5 (4 spd manual) - sold
'63 MGB
'73 MGBGT V8
Reply With Quote
  #8  
Old 11-14-2009, 08:18 AM
Registered User
 
Join Date: Mar 2006
Location: Atlanta, GA
Posts: 121
You might try replacing the iginition switch. I had all sorts of strange electircal problems with my 1970 300SEL. Replacing the ignition switch resolved them. I think the contacts in the old switch had worn so it didn't make good contact all the time.

John

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 05:55 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2024 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page