1.9 Mi16 Coilpack Earthing Fault

[Paul_13 212 1 Cars]

A mate of mine on here has got a 205 rallye in white, which we have treated to a Mi engine.

We've swapped the tank, fuse box, loom etc. from a 1.6gti 205

 

Now we've got this problem where you rev it hard and it cuts out.

If the coil pack isn't bolted to the inlet it revs freely.

 

Now as a temporary measure we've earthed it again in a few places and its working ok. Is there another issue I should be worried about, or leave it as it is?

[Tom Fenton 1,526]

Sounds an odd one. The coilpack is normally earthed somewhere so it could be that its the coil on its last legs and about to give up on you? In the past I've had a coil expire without any warning at all in my old 405 Mi leaving me stranded so I would advise your mate to carry a spare and a couple of spanners about until you've bottomed the problem!!

[Paul_13 212 1 Cars]

Brand new coilpack mate, come to think of it we had the same problem over a year but it sorted itself out and strangely come back after it had been running for a week or 2 fine.

 

Bit of a weird one.

 

I've no idea on the history of the loom etc

[GLPoomobile 958]

I'm shooting from the hip on this one, but.....could it be that there is a break in one of the wires (the +VE supply for instance), which manifests when bolted to the manifold and the engine moves forward when revved, putting some tension in to the loom. And when you move the coil to another location, the loom is not moving and it's fine. But is is working fine with the additional earths whilst bolted to the manifold? Looking at my loom schematic it's not clear which is the earth on the coil (and I can't remember) - it doesn't look like it has a specifi earth and possibly earth's via the ign amp. Or is it through pin 4 on the 6 brown plug under the dash?

[Paul_13 212 1 Cars]

I can see where your coming from steve and it makes sense.

It works even if one of the bolts is missing, aslong as the whole bracket doesn't touch the inlet it starts!?

 

There's a small blue wire with a plastic terminal connector on the same loom as the coil pack plug, which has a 12v feed.

Nowhere near to plug it into though...

[Mikey S 29 1 Cars]

I can see where your coming from steve and it makes sense.

It works even if one of the bolts is missing, aslong as the whole bracket doesn't touch the inlet it starts!?

 

There's a small blue wire with a plastic terminal connector on the same loom as the coil pack plug, which has a 12v feed.

Nowhere near to plug it into though...

 

i'd check the insulation around the coilpack as it sounds like its tracing a path to earth through it.

[Anthony 1,000]

There's a small blue wire with a plastic terminal connector on the same loom as the coil pack plug, which has a 12v feed.

Nowhere near to plug it into though...

That's where the RF suppressor would normally connect AFAIK, but I don't think that I've ever seen one on an Mi16 - certainly it's not a problem it being disconnected.

 

Very odd sounding fault though, as (in very simple terms) the coil has a constant positive and is momentarily earthed via the ignition amp to charge the coil, the coil then discharging and creating a spark through the dizzy cap and sparkplug when that earth is released. The coil body doesn't need an earth to work, but clearly being bolted to an earth shouldn't break it given that the coil itself is insulated!

 

My guess is that either the coil isn't insulated properly or there's something very odd going on with the earths on that car/loom.