Wiring Fault

[Simon-S14]

Little bit stuck on this one. for the record its a R32 skyline

had a flat battery and i got a mate to put jumpers on the battery with a fully charged one and terminals got crossed up the wrong way.. a relay went nuts and popped 3 fuses and the ECU.

put a good ecu in there and replaced all fused and went to start it and it blew another fuse straight away. Its the fuel pump fuse under the dash. some where in the fuel pump circuit it has a dead short. have unplugged the pump and it still blows. unplugging the relay stops the fuel blowing.

with the ECu disconnected and all efi relays unplugged. it still does if i manually earth out the fuel pump relay it so i have eliminated the engine loom side of things.

i'm a little stuck on it.. the fuel pump relay has two sets of wires.. theres the power wire that comes from the fuse itself.. thats blue/black and doesnt appear to have condiduity to the chassis (if it did it would blow the fuse all the time not when the relay is activated) the black/yellow wire that gets powered by the relay to provide 12V to the fuel pump DOES however have a dead short to the chassis. now im stuffed if i can find out where the wire goes to the front of the car as it branches off in the boot to the fuel pump and to the front.

any help would be great!

Edited August 8, 2010 by Simon-R32

[DVS JEZ]

cut the black yellow wire where its easily accessible near the relay, then run a new wire to the fuel pump.

but before you do this disconnect the fuel pump and see if it still blows the fuse

[Simon-S14]

i have done this. fuel pump isnt plugged in at all atm. still blows.

dont really wanna cut and run a new wire,. would like to fix it

[hr31gts]

Clearly the dead short is between the relay and the fuel pump connector (or maybe a broken relay - But highly unlikely). Pain in the arse to find that short, better off running a new wire from the relay to the fuel pump. Don't forget to cut the old wiring BOTH sides, otherwise you will still get the shorts. IF you decide to pull power from another wire for what ever reason, MAKE SURE you fuse it

[Decs31]

if you disconnect the wire where it runs into the relay and also from the pump (like you have) then switch it on, does the fuse blow? if not then the short is in the wire from the relay to the pump. im pretty sure you've worked out thats the issue anyway. i suspect your gonna have to pretty well replace that wire entirely.

if you get a wire hot enough like you probably did, you can melt the insulation off it pretty much all the way along it without too much effort. therefore it can have a million shorts all along its length.

im not an expert on the basic layout of an r32 but i'd asume that under the drivers kick panel there will be a large plug that the loom to the rear of the car connects to. if so disconnect it and see if the pumps wire has shorts there. at least it will determine if the short is before or after the plug. if its after (closer to the plump) it will be far less of a pain in the arse to replace.

[jeffworld2]

If you are trying to chase a wire that is shorted to the chassis, you will find a hell of a lot of them. they are called grounds.

Run a new wire from relay to pump neatly under the carpet etc. and get back to driving.

[Simon-S14]

If you are trying to chase a wire that is shorted to the chassis, you will find a hell of a lot of them. they are called grounds.

Run a new wire from relay to pump neatly under the carpet etc. and get back to driving.

im not not sure if your being serious here or not.. but a ground wire or earth wire is a lot different to a power wire that it shorted out. a dead short is what i have and am trying to find.

but yes.. running a new wire looks to be the fastest way out of this problem