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View Full Version : Ignition fuse blowing, advice needed with electrical short issue



mgforum
29-05-2012, 04:15 PM
I have spent most of the day trying to locate an electrical short causing me some problems, please read below:

TR Magna 4 cylinder, was running fine until lost ignition electrics other day while driving, just prior to this I noticed that the fuel guage had fallen to empty and fuel light was on although there was a quater of a tank of fuel. Gauge has now gone to full with fuel warning light still on...

Discovered 30amp ignition fuse under bonnet was blown and replaced it to get me home, by the time I was home noticed an electrical burning smell.

So far, I have found and replaced melted wires at the ignition key switch and chased the heating of the loom to the fuel relay unit which looked a tad cooked with melted wires. Both replaced and wires seperated but still the loom is heating. I have even cut back loom insulation at several points to check condition of wiring and there are no problems except for at the ignition switch and fuel relay? Strange

Strange thing is this only happens when the engine is running, but does not heat up with the ignition just in the ON position.

It seems to relate to something to do with fuel wiring?

As it runs on gas, I even tried disconnecting all wires from petrol tank (both pump and sender) but this did not resolve the problem.

The heated loom also seems to lead towards the engine coil, does anyone know if this can SHORT OUT and create an earth which could cause the heating.

I have read forums for hours and cannot find a similar problem, except for petrol gauge sender recall on later models, dont think it's relevant to the TR's.

I know there are some great minds and experience on this forum and I would really appreciate some feedback or advice as I am now at a loss. :tired:

magnaman89
29-05-2012, 05:43 PM
welcome to amc
as you have had melted wire,s . autolec would be the best to find your short
like you i would be looking at the fuel pump/gauge electrics
maybe someone else here will be more help
i also ask all new vic members . where in vic are you

mgforum
03-06-2012, 12:30 PM
I have located the hottest wire and start of heat source is the BLACK/BLUE TRACE wire at the fuel pump relay located near the ECU.

The short burnt out the first relay and I have replaced it with no luck of stopping the short. Can't detect heat without engine running, so thought possibly alternator...

I have also disconnected the following during testing:
FUEL PUMP & FUEL TANK SENDER - Wired plugs at the tank
ALTERNATOR

Still have slight heating through entire loom back to Ignition and slightly towards the coil

Fuel guage on dash still rising with ingnition on while low fuel light is on.

It has something to do with the fuel system, but where...?

Please, any advice would surely help...

Can't justify throwing big bucks at this vehicle, hence no Auto Elec to date.

:eeek:

magnaman89
04-06-2012, 10:35 PM
fuel pump relay only gets power when the engine is running .
your whole loom may be fried
im in the valley and have a spare loom