[W126 Coupe] Fuel Pump Issue

[Richard Hallberg]

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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