Took engine in and out a few times. Ignition fuse keeps popping now on "ON" position (no cranking)

Wire diagram below. As Fuse F4 keeps popping instantly, is it safe to say anything that I have marked red could be the problem?

I have removed every singly accessory fuse including lamba sensor, fuel pump etc. Fuse still pops instantly.
Severe short circuit.

it won't be the HT side of things, -distributor, sensor, or plugs, (30, 32 & 31)
it wouldn't be the brown wire earthing the amp either.

I would put a bulb across the fuse terminals, (test with a 5W 12V bulb first)

then I would disconnect the ignition amp, see if it still draws such a high current.

my guess would be a short in the fuse box itself.

On the HT side of things

28, 29, 30, 31 & 32 are not being used as im running bike carbs with stand alone ECU megajolt.

Unplug Everything no fuse and check continuity to ground at all points.
Any short will show readily as continuity to ground.

Angel,

so volt meter set to continuity. and one lead on ground points and other lead on where? Fuse box points?

And if i hear buzzing noise then theirs problem?


Does ignition switch obviously need to be turned on for this testing?

quote:

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Originally posted by bikecarbfred
On the HT side of things

28, 29, 30, 31 & 32 are not being used as im running bike carbs with stand alone ECU megajolt.

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quote:

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Originally posted by bikecarbfred
Angel,

so volt meter set to continuity. and one lead on ground points and other lead on where? Fuse box points?

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quote:

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Originally posted by bikecarbfredAnd if i hear buzzing noise then theirs problem?


Does ignition switch obviously need to be turned on for this testing?

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quote:

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Originally posted by gremlin1234

quote:

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Originally posted by bikecarbfred
....have you perhaps terminated a random black wire to chassis? like you would on a lucas loom?

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Being marked Sw = Schwarz (Black) this must be the culprit.

[Edited on 2/11/2019 by Angel Acevedo]

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bikecarbfred - 11/2/19 at 07:38 PM

if on connector 28 , if all three wires were cut and taped up together, that would 100% cause a short circuit to blow fuse number 4?

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wylliezx9r - 11/2/19 at 07:43 PM

quote:

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Originally posted by bikecarbfred
if on connector 28 , if all three wires were cut and taped up together, that would 100% cause a short circuit to blow fuse number 4?

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Yes it would. Tape them up individually or use terminal blocks.

[Edited on 11/2/19 by wylliezx9r]

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bikecarbfred - 11/2/19 at 07:48 PM

i didnt do any multimeter testing. just saw those three wires loosly taped with electrical tape.
i undid the tape and noticed the were all touching each other.

not sure how the car drove for last two years.
i might have squeezed the tape in last few weeks while doing engine work causing the wires to touch even more.

anyway no fuse popping now.

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gremlin1234 - 11/2/19 at 09:40 PM

quote:

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Originally posted by bikecarbfred
if on connector 28 , if all three wires were cut and taped up together, that would 100% cause a short circuit to blow fuse number 4?

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yes 100%,
but they didn't do a good job of joining them in the first place, if only now does it blow fuses.
I don't know if you should tie connector 28-2 Gn/Ro (green/red) high or low, but from looking at the circuit, I think best to leave it 'floating'

edit: it would have worked for the last 2 years, because the circuit doesn't do anything, Why did you check the fuse and then find it blowing?

edit2: well done for finding that!

edit3: remove fuse 4 it doesn't do anything, then it should all play nicely ;-) but do terminate the other end or the sw (black) wire cleanly too


[Edited on 11/2/19 by gremlin1234]

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bikecarbfred - 12/2/19 at 06:50 AM

gremlin, i can't remove fuse 4.
i need it for megajolt and edis coil because it's the only slot that stays live when cranking i believe so the sparks plugs can fire when cranking which is crucial.

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