Dodgy Coil?

Wingnut · Post by **Wingnut** » Mon Sep 24, 2007 11:27

70 mph (honest

) on the M25 friday evening. All of a sudden no engine

. Alturnator light on. Prior to that everything had been fine and all dials saying what they should.#

On the hard-shoulder it will chugg over but not fire at all. Automatically assumed that it was related to the imobillisor that I had just had fitted so AA recovered me home. (Not bad going having only had the car less than a week and it has already left me stranded on the hard-shoulder

)

Next morning I go out to see if I can sort it out/ring the fitters who did the imobillisor and the blooming thing starts first time

It turns out it is nothing to do with the imobillisor as that would have meant it wouldn't even have turned over. With it working it is hard to identify what the problem and it has not happened since.

I assumed that the coil must be on it's last legs and had just got to hot and given up. A night of cooling down restored it and hence it started the next morning. Any other likely reasons? Is there anything else in the ignition that would stop and then start working?

Oh, and it never seems to have trouble with hot starting so I am discounting that as the cause on the hard-shoulder.

Cheers,

W.Nut.

amarshall · Post by **amarshall** » Mon Sep 24, 2007 11:42

Dizzy cap, HT leads, ignition amplifier, rev. limiter are all possible sources of electrical failure and *could* exhibit the symptoms you suggest.

Usual advice is to start with the cheapest/easiest and work from there.

robertverhey · Post by **robertverhey** » Mon Sep 24, 2007 12:21

Check the continuity of wires between ign amplifier and dizzy. Jiggle the wires while doing this, it might have a dry joint like mine did. Five minutes with a solder iron fixed it. But it took half a day to find....

Robert

Tanz · Post by **Tanz** » Mon Sep 24, 2007 13:10

http://www.lotusexcel.net/phpbb/viewtop ... highlight=

I had a similar problem this year ( see link)Conclution was ignition modual but before you go to the expence of changing stuff (as I did) Roberts advice seems good to me.

Cheers,

Phil

Steve C · Post by **Steve C** » Mon Sep 24, 2007 13:18

I've had two ignition modules (in the dizzy) fail over the years, the first had fractured wires where the dizzy base plate rotates with the vac advance - this caused a misfire as throttle position (and hence vac) changed. The second shorted out internally as the engine warmed up - reduced coils = reduced induced EMF = voltage too low to trigger the ignition amp.

If you repeat the hot / cold problem, you could stick a voltmeter (low AC range) on the input to the ignition amp, watch the voltage at crank revs when cold and hot/not starting. Any significant difference indicates bad connection / ignition pickup issue.

Wingnut · Post by **Wingnut** » Tue Sep 25, 2007 09:02

Thanks for all the advice chaps.

I had checked all continuity and usual culprets on saturday and not found anything untoward. As I said it is obviously going to be hard find a fault when it is intermittent. I will get a replacement coil to carry in the boot incase it happens again. Any idea of a source and price for an ignition module if is turns out to be the same problem as Tanz?

Cheers,

robertverhey · Post by **robertverhey** » Tue Sep 25, 2007 09:22

Lucas AB14 unit, as fitted to many Jaguars. Usually appear from time to time on Ebay. I keep one in the glovebox.

Presently one there: item 230174755776 but you shouldn't need to pay that much. From memory I paid $10US for one from the States

Hope this assists

Robert

omendata · Post by **omendata** » Sun Oct 21, 2007 23:11

£30 from Lucas spares depot!

DANNYRADLEY · Post by **DANNYRADLEY** » Mon Oct 22, 2007 08:08

Hi just bought one powertrain module £18 local motorspares shop.

Wingnut · Post by **Wingnut** » Thu Nov 01, 2007 17:37

Still not managed to get this sorted and it left me stranded again at the weekend.

Anybody tell me if I should have a ballast resistor connected to the coil? There doesn't seem to be one