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Author Topic: Killing a DIS  (Read 835 times)

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Martin_1962

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Killing a DIS
« on: 15 September 2006, 20:39:41 »

OK I am sure I am right here.

Would having a trigger wire for a pair of coils earthed burn out those two coils?

I have been told no - it was my fault (playing with pipes he said) - but I am sure it was a short.

Annoying emails from the LPG installer - I have told him I won't contact him again  but to remove my old car
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Fuse 19

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Re: Killing a DIS
« Reply #1 on: 15 September 2006, 21:38:30 »

It could do.....the modern coils are pretty small, keeping them permanently earthed tends to fry them.

The real controllers only apply 0V long enough for the coil to fully energise the ferrite/iron.
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Fuse 19

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Re: Killing a DIS
« Reply #2 on: 15 September 2006, 21:46:02 »

The other thing that kills them is operating them with no load i.e. no plugs attached or the leads disconnected
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Martin_1962

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Re: Killing a DIS
« Reply #3 on: 15 September 2006, 22:13:54 »

Thought so - as before don't want to deal with the person again, he has been a bit rude but I am staying above that, they have seen my CIAO review which points here, so if he starts reading he will find posts like above!!!!

I just wish I had heard of DIY gas before
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Matchless

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Re: Killing a DIS
« Reply #4 on: 15 September 2006, 22:38:25 »

Grounding one or more trigger leads will kill a coil fairly quickly.

When operating normally, the current is determined by the coil inductance and for how long the current is turned on (ecu calculates how much time to allow between turn-on and when it needs the spark) If there is no time limit (wires are grounded) then current will increase until limited by the battery voltage and coil resistance. This could be anything between 3A and 12A depending on coil design. This energy has to be dissipated as heat so the coil heats up and eventually the insulation cant take it any more and melts.

Old points based ignition systems had no means of controlling coil current so the coils were designed with high resistance to limit the heating effect if the engine stopped with the points closed and ignition left on. They still got too hot to touch after 15mins or so. The problem with this was that it limited the energy available in the spark and it was insufficient for todays engines usin leaner mixtures, exhaust gas re-circulation etc.

MarksDTM....can you measure the primary resistance of the coil you had earlier?
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Fuse 19

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Re: Killing a DIS
« Reply #5 on: 16 September 2006, 09:48:42 »

Dc coil resistance measures at 1.3 ohm's (DC resistance being the key thing here as the coil is permanently energised.....AC would be much higher)

So using a quick sub o ohms law we get

W=(VxV)/R

Assuming V= 12V (it will be much more with the engine running) we get

110W!

This would cook the coil and cause it to fil....your LPG installer is clearly a Muppet who doesn't have a grasp of the basics (unfortunately not un-common)
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Martin_1962

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Re: Killing a DIS
« Reply #6 on: 16 September 2006, 21:15:35 »

The gearbox going into limp, and rev counter jerking made me thing there was a short - but didn't think a wire would have been routed next to EGR and melted on it, as it cooled it reinsulated.

Connecting to coil feed - it broke down an hour after changing wire. THen the lad at work who gave me a lift for a week or two had his coil pack go.

ECU was OK decided to buy DIS couldn't fit it! - waited till I could book into local dealer. Did multimeter check on LPG wiring in mean time found short repaired it.

The installer told me after the swap to coil feed no more warrantee work so I never got the high RPM cut out sorted nor the over pressuring.

This is why I DIYed it on the 2.6!
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