fuel pump electrics on W124 coupe

[nijo61]

Hi can anyone help?
My 300 coupe (124) broke down on the motorway the other evening. RAC brought it home. I couldnt hear the fuel pumps so automatically thought it was the relay, Ive checked all fuses, swapped both the relay and the ovp from my other car (so I know they are OK) - no luck. I then checked the connection under the back seat - ran a live to the pumps from the connection- they worked so are ok. Then checked the live to the connection -no power. So the fault is prior to the connection under the back seat - but where? Has any one got any suggestions?

 

[television]

Are you sure that you tried the right relay for the fuel pump.

There will be no power to the pumps after a few seconds on turning on the ignition as the fuel pump relay is designed to cut the power if it does not receive a signal from the crankshaft sensor.

To test this out bridge pins 7 and 8 of the multiplug relay and the pump should run all of the time.

The correct relay is 77 in the link, this is the fuel pump cut off relay.
http://www.detali.ru/cat/oem_mb2.as...GM=717.430&CT=F&cat=501&SID=54&SGR=040&SGN=03

If the pump does not run with 7 and 8 bridged then the wire could be faulty

 

[nijo61]

thanks will give it a try is there another relay other than the one behind the battery?

 

[television]

Yes they are in the fuse box