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80 450SL
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7 Posts
Discussion Starter #1
I have seen a similar thread, but I wanted to start a new one as the previous thread did not solve my problem.

Jump 30 - 87 (connector pins 1 & 2) on the fuel pump relay connector, and it starts and runs fine

Measured 12+V from pin 2 to Ground
Measured 12+V from pin 2 to pin 5
Not measuring anything from pin 3 to Ground
Not measuring anything from pin 4 to Ground

With 30, and 87 jumped lowering the Air Flow Plate causes the screech of the fuel

Any helpful advice is greatly appreciated. Trying to get the car running for my father in law to sell.

Thanks!
 

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1986 560 SL
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7,356 Posts
Not clear what your problem is.
It starts and runs okay with FPR jumpered?
Starts then stops with FPR in place?
What do you mean "screech of the fuel"?
 

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US spec MB560SL 1986, Audi A4 and A6, Ford Taunus 1964 17M and 2.0 1975
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1,419 Posts
"Not measuring anything from pin 3 to Ground
Not measuring anything from pin 4 to Ground"

- do you mean no voltage value or no resistance value?

FPR has many functions, try to get correct schematics with wire colors. I think it will help you forward with the measurings and determine the root cause(s).
 

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80 450SL
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7 Posts
Discussion Starter #4
With FPR in place car starts for 2 seconds then shuts off
With FPR jumped car starts and runs fine
Screech as in the sound of the fuel spraying when lowering the Air Flow Plate

I read another post describing a test procedure for the Fuel Pump relay
Checking 380SL Fuel Pump Relay - PeachParts Mercedes ShopForum
This says to test power at pin 2, pin 3, and pins 2 and 5. I have no power at pin 3.

I read this manual which says to test pin 2, pin 4, etc.
http://www.startekinfo.com/StarTek/outside/11883/PROGRAM/Engine/107/M117_45/073-165.pdf

I am not sure which is correct, and where to go from here.

Thanks again!!!
 

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80 450SL
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Discussion Starter #7
Thanks I followed that manual prevoiusly and it calls for testing voltage between ground and pin 4. I did not get any village in that pin. Does anyone know where that terminates?
 

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80 450SL
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Discussion Starter #8
I forgot to ask, but is there a way to test the actual relay to ensure that it is good / bad?
 

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1986 560 SL
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7,356 Posts
I forgot to ask, but is there a way to test the actual relay to ensure that it is good / bad?
A new one goes for about $40.
They fail so often, some guys carry spares.

On early 450s, all the relays above the fuse box are interchangeable and can be substituted to test for a dud. I dunno about your 1980 .....
 

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R107 450sl
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10 Posts
Had similar problem some time ago. Although the relay was working on a test bench (bringing 12v to the solenoid closes the circuit) once the relay was replaced, the problem disappeared. Too much for a coincidence I trust.


Sent from my Autoguide iPad app
 

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80 450SL
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7 Posts
Discussion Starter #12
@dugald Thanks for the wiring diagram! That helped it make more sense. I am going to go ahead and replace the FPR, and see what happens. This relay is not one of the cheap ones. It is a 6pin black one that is not interchangeable with the icecube type relays. I'll post back after the relay is replaced.

Thanks!!!
 

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R/C107 Moderator
1986 560SL: '84 500SL: '84 280SL 5 speed: other 107s
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32,357 Posts
Less than $50.00 if you are in the U.S. That's where a completed profile helps.
 

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80 450SL
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7 Posts
Discussion Starter #14
I just added some info to the profile. I am in the states. Where can I get one of those for less than 50?
 
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