Electronic experts....

[Sponge Bob]

Ok guys - a quick connundrum for you - I did a few tests with my multimeter as I'm not getting a spark or check engine light and it threw up this...

My Battery pin on the ECU (which gets 12V with Ignition switch both on & off) get's a nice 12V fine - BUT it's got continuity with the chassis too, i.e. it's earthed out?????

Soooo i'm guessing I've got a wire which has chaffed through and is touching the body of the car or something, but does anyone have hints on where exactly to look/other suggestions in order to find where/how it's earthing out.

I've looked at the diagrams but can't work out where that batt pin wire travels :cry: need some help from a wiring guru...

:driving:

[Murf]

Whats the resistance value (in ohms) you measured, between the +pin and the chassis? Surely if a wire was chafed that badly it would be blowing the efi fuse? It could be getting a slight reading through other components if your meter was really sensitive or set to the wrong range,possibly!
Car electrics do funny stuff sometimes!

[Sponge Bob]

Thanks for the posts chaps - I just did a check with the battery completely disconnected and it's still got continuity between the body and the BATT pin...

Its not blown any fuses I think - which is somewhat worrying!!! :S

[Paul Woods]

i suspect its got some form of resistance to earth through the alternator... the white/red wire that goes to pin A1 BATT also goes to the alternator,try the same test but with the alternator unplugged ash.... just a guess.

[Sponge Bob]

Cheers Paul, will give that a try this eve and report back the results... :)

[Gary Symons]

Ash, did the ecu arrive ok?

If it did I assume it didnt fix your issues.

[Sponge Bob]

Yeah, thanks Gary... pm'd you mate.

[Sponge Bob]

I did some more checks and here's what comes up:

BATT + Alt main power = FULL continuity
BATT + Top pin from round alternator plug = FULL continuity
BATT + One of the bottom pins from round alt plug = SOME continuity
BATT + Body earth = SOME continuity

My EFI relay fusey thing works fine - did a test on that, and the results are exactly the same with the EFI relay pulled, and the alternator plugs off...

I am so confused - but i'm sure it's something very simple/stupid (knowing me lol)....?

[Goldy]

What are you measuring continuity with? Are you measuring it using the resistance setting or the diode / beeper setting? What's the actual reading displayed?

[Gary Symons]

As goldy /\

I would expect you will always get some sort of continuity from the +ve terminal to the body via electrical components that are permanently connected. eg the clock.

[Sponge Bob]

Well - it's measuring with both... the beeper helps as it changes the tone with varying resistance levels.

Maybe that's not the problem at all - but I've done nothing since changing an injector - and I did manage to get a check engine light once, after reinstalling the plugs on the ECU, i.e. it worked for a brief few seconds, but then stopped working after I tried to crank.

[Marksman]

Any oomph left in the battery?

Owen.

[Sponge Bob]

Ai - I've charged it plenty bud, and it gives out a solid voltage...

I just want to see that damn ECU light come on in the dash when I switch her on (and not by just grounding out the W pin on the ECU lol)

[Goldy]

you haven't got a dodgy earth have you?

[Sponge Bob]

Quite possibly mate... is there a systematic way to check for them, or do I have to just manually look around and find the earth points.

[Murf]

All the earth points are shown in the BGB earth point schematic.

[Sponge Bob]

Right - getting much closer...

Went back to basics & took batt cable off starter and tested - it had continuity with the car body... Turns out that my amp power cable was earthing out somewhere, so disconnected it.

Mangaged to get correct lights on dashboard (one red, one orange as opposed to my usual 3 red) so put everything together again happy as Larry(alternator, AFM, and couple other bits) and switched key to on.

Nothing - no lights, so took batt cable on & off to reset things and i'm getting same 3 red lights again.

Did same basic test again but this time the main cable was fine but turns out that the other cable coming from the starter (big white one which goes to alternator and other places i think) now has continuity with earth...

So... anyone have any ideas as to the problem lol

Am just trying to find where this big white wire spans out to to see where it's hitting the earth...

[Tom G]

Just re-read this after seeing your desperation! wanted to sell mine when i had a mystery fuel pump problem which turned out to be a stupid easy fix which I had mis-diagnosed.

I think you may be barking up the wrong tree looking for short circuits - if you're seeing 12v at a terminal, the harness is unlikely to be shorted somewhere. You'd either see smoke, a tripped circuit breaker or a blown fuse, and the battery wouldn't hold charge for long.

Getting back to basics, am i right in thinking that sometimes your ecu gets power and an ignition signal but doesn't turn on the ecu warning light? And you've swapped for a known good ecu and the same thing happens?

[Sponge Bob]

Yeah - tried new ECU, to no avail... I just get 3 red lights on the dash, no orange engine one... doesn't let me pull codes etc, no spark (will crank ok, though makes slightly funny noise).

Now you mention it - it's baffled me why there was no fuses blowing, but at the same time I can't fathom why a 12v signal should be getting contiunity with the chassis??

[jimi]

I think you might be leading yourself up the garden path with the meter.
With the battery disconnected what actual resistance reading are you getting (in Ohms) ? is it steady or fluctuating ?

[Gary Symons]

I think you might be leading yourself up the garden path with the meter.
With the battery disconnected what actual resistance reading are you getting (in Ohms) ? is it steady or fluctuating ?

Agree, like I said before, you will still get a reading from the +ve to the earth with battery disconnected via components like the clock that are permanently connected.

If dash isnt lighting up properly I would check that there is power and a good earth to the ecu first.

[rattymr2]

any news Ash?

[Sponge Bob]

Not yet Mart, do JuJitsu on a Tues which goes to half tennish and knackers me right out - so will be putting everything back together, and testing as the good ECU earth & power tomorrow eve!