can anyone remember what the original earth wire for the fuel pump on a 2wd saff. im sure its the brown next to the black with red stripe in the loom inside the rear pannal. i now the blk and red is the live. i abandand the original wiring fifteen years ago

 

Are you re wiring the fuel pump wiring??

 

hi there glenn no. but i did fifteen year ago i re wired it then from front to back the fuel pump i mean. i abandoned the original fuel pump wiring it comes around the inside of the rear back pannal before it goes through the boot floor to the pump. but what i didnt do was re earth the original earth. looking at the wiring diagram it looks like to me its also earths other stuff including the icv. i just put the new fuel pump earth direct to the inside body work from the pump. the car runs fine but its burnt out x2 ecu which is more than likely an earthing issue. ive got an auto electrician coming out hopefully to sort it im just waiting to see if my ecu can be repared. where the original live comes around the inside of the back pannal which is black with red stripe theres a thick brown one the same size next to it in the same connector. im almost certain this was the earth.years ago wiring diagrams showed what colour they were. the car has run fine for the last fourteen years but two years ago the ecu burnt out and two years later last fukin week another one

 

the fuel pump will earth to the chassis. It absolutely will not run down the length of the car as a wire, and it absolutely will not be connected to the ISCV

There is no possible way a fuel pump can burn out an ecu, because it is not connected to the ecu. ( and only a very very very silly person would try and connect it directly to the ecu )

The ecu will trigger a relay, and this will provide 12v power to the pump when required, which will be wired down the length of the car.

 

thanks for the reply ive basically just had to re trace my steps as a process of elimination. the original wiring didnt go directly to earth from the pump it went up to the inertia cut out in the boot and then back into the loom into and around the back panal. to read a wiring diagram you have to no how to read them properly which i dont. looking at the diagram it does eventually go to earth but not directly. models with lamb sencors share the same earth. and also pins 19 and 1 which are earths that are bolted to the throttle cable bracket and solenoide perg valves cat model. you are correct it doesnt go to the icv on second look the wire crosses over but not teed to it. my main worry is now i didnt re earth this wire bit of a school boy error there. ive just sent the ecu to auto dynamix at newton abbot james worked for motor sport developments at blackpool for a long time running there workshop him and stuart are cosworth gods nobody no's anymore than them about sierra cosworths they started the original tunning scene back in the 90s. theres quite a big voltage drop when the starter motor is engaged . theres no resistance from the main earths to engine or chassis so im fuked if i no could possably be engine loom there five hundred quid. so its beyond me . jamie lamb proffesional auto electrian is coming out early new year

 

I will repeat again.

The earth for the fuel pump WILL NOT go to the ecu. Never ever. It will go to chassis/battery ground. It may go to ground via the inertia switch ( I can't recall if the switch kills ground or the 12v supply ), but that's irrelevant here.

If someone has wired it to the ecu, it is incredibly stupid and no wonder it will cause problems.

It is crystal clear on the wiring diagram I have here ( LHD 3 door ) that the ground wire from pump is brown, and is to same earth point as fuel sender unit also earths to the body. Diagram says close to the tailgate lock.
There is no mention of an inertia switch on this one, but I know some lesser EFI Ford's did still use an inertia. Not sure on a Cosworth

12v from relay is black/red

 

i will re earth that brown wire thats in the loom next the fuel pump live it does have continuity with the chassis so it is earthed somewhere. on your wiring diagram does it show what relay or fused live is for the ecu mine doesnt. theres nothing more that i can do now. i would of thought the fused live would have blown to the ecu not unless some twat has put a nail across it. i did read on a post somewhere that your better of disconnecting the ecu plug before doing any welding which i recently did a month before the melt down and i carried welding just before the first melt down two years ago. but i allways remove both terminals from the battery and put my anti surge protector bridging the terminals which is pointless really as it may need 12v to make the devise work or show that its illuminating the green l e d confirming protection. maybe worth doing this in the future

 

the fused live for the ecu has nothing to do with the fuel pump.

And fuses are to protect wiring, not devices. Unless it is specifically for and very local to the actual device. And even then, it's hopeful that a fuse will protect it.

http://www.cannell.co.uk/Ford_Worksh...20Diagrams.pdf

 

thanks for the wiring diagram i no the fuel pump relay doesnt feed the ecu. finding the ecu relay is the next port of call to see if somebody has smashed a dirty great fuse in there. i will see if i can identify the ecu relay by the colour wires going to it or if the relay has a fuse holder on it ill pull the fuse see if the pin goes dead. im better of leaving it now untill matey comes out early new year thanks

 

relays do not contain fuses. A fuse will not fit in place of the relay. So that's an extremely weird notion. On some setups there may be a fuse located beside a relay holder. Not the same thing.

https://fuseandrelay.com/ford/sierra.html

http://www.bigturbo.co.uk/
http://www.bigturbo.co.uk/main6.htm

And whoever this is with problems, the black/red wire on one relay holder might suggest some relays are inside the car, as black/red is same as fuel pump, at least for the earlier car.

 

thanks again m8 thats what i said if it has a fuse holder on the ecu relay. we no that fuses arnt relays that very well would be a weird notion as you put it