[W126 Coupe] Fuel Pump Issue

[Jay Manek]

Hi Guys,

Its definately not something to do with the pump.. ive been playing around 
and I can hear a click on the relay just before the car cuts out..

A friend suggested changing the start valve (extra injector on manifold) 
which i did and then on they way home I had no trouble... im not convinced 
the issue has gone, probably just a coincidence but we will see.

Im sure something on the engine side is telling the relay to cut out... 
maybe just a dodgy ground?..
It almost always does it when the car is at low revs, its never done it on 
the run... yet...

I hardly use the car much, its kept in my garage so it may take me some time 
to get to the bottom of it.



Many Thanks & Regards

Jay Manek | www.mercland.com| 07716 349949

--------------------------------------------------
From: "Richard Hallberg" <rkhallberg at mindspring.com>
Sent: Thursday, October 01, 2009 2:29 PM
To: "Mercedes Coupes Mailing Lists" <mbcoupes at mbcoupes.com>
Subject: Re: [W126 Coupe] Fuel Pump Issue


> Jay,

>

> Just a thought - it sounds like the circuit opens after passing current 

> for a period and my thought is that it may be a heat-related short in the 

> pump motor windings, or other electronics.  I would test voltage at the 

> fuel pump(s) and monitor the running pump until the engine cuts out.  If 

> the voltage is still available at the pump, I think (without really 

> understanding the control circuitry) it indicates a faulty pump.

>

> Please be aware that I am a newbe (6mo.) 1991 560 SEC owner/driver.

>

> Richard Hallberg

>

> Jay Manek wrote:

>> Hi All.

>>  Well ive changed the relays... i tried a new one and ive tried spare old 

>> ones but no good.. The pump runs for a few minutes on a new relay but 

>> then cuts out.

>>  Help!!

>>  Many Thanks & Regards

>>  Jay Manek | www.mercland.com <http://www.mercland.com>| 07716 349949

>>

>> *From:* Iain Gunn <mailto:igunn at bmts.com>

>> *Sent:* Thursday, October 01, 2009 1:27 AM

>> *To:* Mercedes Coupes Mailing Lists <mailto:mbcoupes at mbcoupes.com>

>> *Subject:* Re: [W126 Coupe] Fuel Pump Issue

>>

>> these relays have changed over the years, original was 5 pins and one 

>> blank. I ordered a new one once and it came with 4 pins,1 blank and 1 pin 

>> missing. It was the wrong relay. Found the correct one and no problem.

>>

>>     ----- Original Message -----

>>     *From:* Jay Manek <mailto:jaymanek at hotmail.com>

>>     *To:* Mercedes Coupes Mailing Lists <mailto:mbcoupes at mbcoupes.com>

>>     *Sent:* Wednesday, September 30, 2009 1:32 PM

>>     *Subject:* [W126 Coupe] Fuel Pump Issue

>>

>>     Hi all,

>>      Need some help.

>>      My 560 SEC decided to cut out on me at the weekend and I was stuck

>>     on quite a busy road. I found that the fuel pump wasnt running. I

>>     phone an auto electrician friend  who suggested bridging terminals

>>     30 and 87 on the fuel pump relay, I did this and it fired into

>>     life... so managed to complete my 160 mile journey home.

>>      Now im back home and a new relay has not done the trick, still

>>     does not fire up the pump unless i bridge the pins.. So it must be

>>     something associated with the relay?...

>>      Looking at the wiring diagrams there are various items connected

>>     the fuel relay... anyone any ideas where I should start looking?

>>      Many Thanks & Regards

>>      Jay Manek | www.mercland.com <http://www.mercland.com>| 07716 349949

>>

>>

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>> Postings remain property of MB Coupes, L.L.C.

>

> The MB Coupes Website!

> W126 SEC Mailing List

> Postings remain property of MB Coupes, L.L.C.

>