[W126 Coupe] Fuel Pump Issue

[Jay Manek]

Hi Axel,

That is a theory that may be worth looking into as when I measured the voltage at the battery it was barely topping 13V at idle... ill check with my other SEC but im guessing it needs to be a little higher?!


Many Thanks & Regards

Jay Manek | www.mercland.com| 07716 349949


From: Axel Wulff 
Sent: Sunday, October 04, 2009 5:46 PM
To: mbcoupes at mbcoupes.com 
Subject: Re: [W126 Coupe] Fuel Pump Issue


Just a hunch, but have you checked the alternator?
 
If it only happens at low revs, and the battery/alternator are not performing properly, the relay may not see enough voltage.

Regards,
Axel J. Wulff
610-731-5453 Cellular
610-572-4611 Home



 

> From: jaymanek at hotmail.com

> To: mbcoupes at mbcoupes.com

> Date: Sun, 4 Oct 2009 14:32:14 +0100

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

> 

> 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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