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  #16  
Old 07-01-2008, 05:48 AM
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Cool Ovp?

Okay, what exactly is an OVP relay? Is it located diretly above the fuse box? what am I looking for? Would the OVP relay cause it not to start?

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  #17  
Old 07-01-2008, 06:34 AM
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OVP relay

Okay, got the OVP relay out, the 1oA fuse on top is fine, but from reading other posts, am I to assume that doesn't mean the OVP relay is okay?
Does the OVP stand for Over Voltage Protection? Just curious. Should I order an OVP relay? Got any ideas? Here is what is not working:
1. dash lights
2. power windows
3. mirrors
4. horn

Radio works, turn signals work, brake lights work, hazard light works, headlights work.

Continues to turn over strong, still sounds fuel deprived. Still no humming coming from fuel pump, which used to be obvious when it kicked on. My gut tells me it is in the fuse box area since when the box was shoved tight up against the fuse box, it is since that day that this all started to happen. I think the box forced something to short out. This car ran like a demon, never any starting problems, ever. He used it every week end, it was very dependabl, even after sitting for 5 days each week, it always popped right off. I don't think it is a coincidence, I think it is related. Thanks to all that are trying to help me work through this...I appreciate it. He works so hard, but when he gets in this car and puts down the top, his whole disposition changes, this car brings him such joy. I have to figure this out. SO, thanks.
He is a big strong man, by the way, but he is working 12 hours a day, 6 days a week, I don't have the heart to ask him to help me. So, I will muddle through till I have tried whatever ya'll tell me to try.
Just a Girl -
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  #18  
Old 07-01-2008, 06:38 AM
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OVP relay

Okay, I know how to use a voltmeter, what am I testing with it? I used to be in Engineering so I know about volts and ohms and amps. Just tell me where and what to check. My sister is an electrician so if it gets beyond me I will call her.
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  #19  
Old 07-01-2008, 07:36 AM
LUVMBDiesels's Avatar
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Posts: 2,207
Do you have the wiring diagram for the car? I would trace out the wires from the fusebox to the fuel pump with a continuity testor to see if there are any breaks. Since you are thining it must be near the fusebox, I would start there. All the things that are not working are controlled by relays with the exception of the dash lights. Start by checking the wiring under the relay sockets. Also check to make sure that your ground wires did not get disconnected (brown wires are usually ground in MB)

If you have the wiring diagram, you can see which of the relay sockets need to get jumped to do things like make the windows work and start the fuel pump.

Good luck
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  #20  
Old 07-01-2008, 06:23 PM
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Talking 560sl problem

where can I purchase the wiring diagrams so I can begin my quest!!!!!!
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  #21  
Old 07-01-2008, 06:52 PM
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1981 Mercedes-Benz 300SD
 
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Location: University of Georgia
Posts: 1,082
Heres the relevant pages from the electrical manual


Edit:
It shrank the attachments, heres the full size,

http://img356.imageshack.us/img356/5520/pagesfrom126from86page1wm1.png
http://img48.imageshack.us/img48/8454/pagesfrom126from86page2ns1.png
http://img242.imageshack.us/img242/5214/pagesfrom126from86page3go8.png
http://img180.imageshack.us/img180/2383/pagesfrom126from86page4jp0.png
Attached Thumbnails
I am a girl, need help, 1986 560sl won't start, tries hard.-pages-126from86_page_1.jpg   I am a girl, need help, 1986 560sl won't start, tries hard.-pages-126from86_page_2.jpg   I am a girl, need help, 1986 560sl won't start, tries hard.-pages-126from86_page_3.jpg   I am a girl, need help, 1986 560sl won't start, tries hard.-pages-126from86_page_4.jpg  
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1981 Mercedes-Benz 300SD | Blown engine, rebuilding someday...
1981 Mercedes-Benz 300SD | Rear ended, retired in garage.
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  #22  
Old 07-01-2008, 08:19 PM
LUVMBDiesels's Avatar
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Looking at the diagrams quickly it looks like there should be power on pin 9 of the fuel pump relay when you turn the key to "on" the relay should send power to pin 7 to run the pumps. I would try sending 12V down the line from pin 7 to see if the pumps are working...
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"I have no convictions ... I blow with the wind, and the prevailing wind happens to be from Vichy"

Current
Monika '74 450 SL
BrownHilda '79 280SL
FoxyCleopatra '99 Chevy Suburban
Scarlett 2014 Jeep Cherokee
Krystal 2004 Volvo S60
Gone
'74 Jeep CJ5
'97 Jeep ZJ Laredo
Rudolf 86 300SDL
Bruno '81 300SD
Fritzi '84 BMW
'92 Subaru
'96 Impala SS
'71 Buick GS conv
'67 GTO conv
'63 Corvair conv
'57 Nomad
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  #23  
Old 07-01-2008, 09:50 PM
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300SD81's and LUVMBDIESELS, Thanks for staying with me through this, all you guys. Now that I have the diagrams I can start this week end (looks like it might take awhile). I did a quick visual check of the brown ground wires and they look perfect, matter of fact all the wiring looks new so this may take awhile, nothing weird or obvious other than that old melted spot under the steering wheel which I have no idea why that is like that. If it wasn't a Florida car I would think the wiring was new. all the lugs look new, the wires look new. I am trying to contact previous owner to ask if he replaced wiring harness. Anyway, thanks, I will start this week end.

One more question, can I attempt to start the car without the OVP relay in, someone mentioned trying that but wanted to verify that as an option for diagnostic purposes only. They aso mentioned leaving out the fuel pump relay and trying that too.
Thanks again, whatever I find, I will keep writing in case this happens to someone else.
Thanks, Mahouna
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  #24  
Old 07-02-2008, 08:12 AM
LUVMBDiesels's Avatar
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Quote:
Originally Posted by mahouna View Post
300SD81's and LUVMBDIESELS, Thanks for staying with me through this, all you guys. Now that I have the diagrams I can start this week end (looks like it might take awhile). I did a quick visual check of the brown ground wires and they look perfect, matter of fact all the wiring looks new so this may take awhile, nothing weird or obvious other than that old melted spot under the steering wheel which I have no idea why that is like that. If it wasn't a Florida car I would think the wiring was new. all the lugs look new, the wires look new. I am trying to contact previous owner to ask if he replaced wiring harness. Anyway, thanks, I will start this week end.

One more question, can I attempt to start the car without the OVP relay in, someone mentioned trying that but wanted to verify that as an option for diagnostic purposes only. They aso mentioned leaving out the fuel pump relay and trying that too.
Thanks again, whatever I find, I will keep writing in case this happens to someone else.
Thanks, Mahouna
I don't know about starting the car w/o the fuel pump relay. It controls a bunch of things. I would just jump 12V to socket #7 and see if the fuel pumps run.

I am not sure if the OVP relay can be jumped to start the car
__________________
"I have no convictions ... I blow with the wind, and the prevailing wind happens to be from Vichy"

Current
Monika '74 450 SL
BrownHilda '79 280SL
FoxyCleopatra '99 Chevy Suburban
Scarlett 2014 Jeep Cherokee
Krystal 2004 Volvo S60
Gone
'74 Jeep CJ5
'97 Jeep ZJ Laredo
Rudolf 86 300SDL
Bruno '81 300SD
Fritzi '84 BMW
'92 Subaru
'96 Impala SS
'71 Buick GS conv
'67 GTO conv
'63 Corvair conv
'57 Nomad
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  #25  
Old 07-03-2008, 05:25 PM
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Join Date: Jun 2008
Posts: 16
starting 1986 560sl without ovp relay in

Originally Posted by mahouna
300SD81's and LUVMBDIESELS, Thanks for staying with me through this, all you guys. Now that I have the diagrams I can start this week end (looks like it might take awhile). I did a quick visual check of the brown ground wires and they look perfect, matter of fact all the wiring looks new so this may take awhile, nothing weird or obvious other than that old melted spot under the steering wheel which I have no idea why that is like that. If it wasn't a Florida car I would think the wiring was new. all the lugs look new, the wires look new. I am trying to contact previous owner to ask if he replaced wiring harness. Anyway, thanks, I will start this week end.

One more question, can I attempt to start the car without the OVP relay in, someone mentioned trying that but wanted to verify that as an option for diagnostic purposes only. They aso mentioned leaving out the fuel pump relay and trying that too.
Thanks again, whatever I find, I will keep writing in case this happens to someone else.
Thanks, Mahouna


Okay, to see if fuel pump relay works I short pins 7 and 8 or 30 and 87 on the relay or just apply 12 volts to pin 7. Try that this week end, but back to other question, looking at schematics it appears if the OVP is junk it appears 12V never gets to the fuel pump relay, so could I not leave out the OVP relay and try to fire it off? Granted, my car could burst into flames but I have insurance, ha, ha!!!
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  #26  
Old 07-03-2008, 11:25 PM
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1983 300SD, 4 speeed
 
Join Date: Jul 2006
Location: Raleighish, NC
Posts: 664
Just a thought--on my '94 c280 there is a newer OVP with a 15amp fuse. I do not know if your car has an upgraded OVP or not but maybe it's worth looking into. Good Luck.

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