No (accu) spark - test sequence?

[Stuart Giles]

I see from their website that copper leads can cause interference. Could that mean it could kill the unit? I didn't know that when I bought it.

When aftermarket Electronic ignition manufacturers advise against Copper leads and/or mandate carbon string leads it's often because their electronics don't stand up so well to the much larger pulse passed back from a Copper HT lead through the coil -this the so called back EMF; on a points system, this back EMF will be absorbed by the condenser. I learned this lesson  the hard way with two failures of Lumenition  Performance modules in the space of a couple of months; one of the failures was while sitting on the dummy grid at Silverstone.

The imperative of carbon leads for this product  was buried somewhere on the Lumenition website, but wasn't referenced  in the fitting instructions that came with the kit.

[Hedd_Jones]

The poor starting due to voltage drop is a common feature on cars with electronic ignition. 

My mate Tim had a Ginetta G15. Rear Hillman engine. Battery at front. 

With the original wiring it seems it was pretty marginal even with a new battery and the swine would regularly not fire. It took some advice from the dizzy doctor (tim was going to go back mechanical) to find the problem. He ran a wire from the hot end of the starter solenoid to the coil via a switch and it started first time every time for a week. So the wiring was modified.

[AustinWood]

I have been doing some testing on my 1929 fabric saloon ignition wiring. It has an Accuspark distributor.
For some time the car has been reluctant to start using the starter motor and never will if the engine is cold. The starter works well and turns the engine over at a good speed. It starts first pull using the starting handle.
My battery is fully charged and is connected to a conditioner to keep it topped up.
The battery voltage is 6.3 but when cranking this falls to less than 5V which I suspect is too low to trigger the Accuspark. I've long thought this to be the case but haven't got round to measuring it until today. The voltage at the coil is the same, so the wiring must be OK with no bad contacts. A direct connection between battery & coil makes no difference. The other clue is that sometime the engine starts just as the starter is switched off because the voltage rises at that moment. The starter also works if the engine is warm and hasn't been stopped for long.
This implies that the battery cannot supply the current required by the starter and at the same time supply the voltage required for the ignition. With a hot engine the power needed to turn the engine is less so the starter works OK.
My guess is that the battery is getting tired and maybe a new one is the solution. However as the car starts very easily on the handle I'm not that bothered.

[Nigel Ricardo]

Austin , I am getting the same as you with 12 volts and its a new fully charged battery, the engine won't fire when the starter is engaged, when I release the starter it fires, when the engine is warm there is no starting problem.

[JonE]

IgnitionCarParts also do a unit, and they said that theirs triggers at around 4.5V.

Stuart, does that mean that you would religiously maintain carbon leads for any such devices now? I'm intrigued that Ruairidh - one of the key big mileage users - has been absolutely fine with copper.

Is there any disadvantage with using Carbon leads for any other variables to do with Sevens? They aren't very expensive, so not worth not putting them on unless there are...

[Stuart Giles]

Stuart, does that mean that you would religiously maintain carbon leads for any such devices now? I'm intrigued that Ruairidh - one of the key big mileage users - has been absolutely fine with copper.

Is there any disadvantage with using Carbon leads for any other variables to do with Sevens? They aren't very expensive, so not worth not putting them on unless there are...

I cured my particular problem by modifying a 1980s "original equipment" General Motors electronic ignition system to fit my car, OEM electronic equipment tends to be far more robustly designed  than aftermarket kit, so my racing car still runs with copper leads and hasn't had an ignition failure in several seasons competition. I run the same electronic module on my tow truck with Copper leads, been running for many thousands of miles without any issues.

But if I was still using one of the aftermarket electronic setups, I would use carbon leads with it. Carbon string HT leads do attenuate the back EMF in a way that Copper leads don't; IMO using Copper leads won't necessarily mean your ignitor module will go phut tomorrow or even  the day after, but it does increase the risk of a failure.

[JonE]

Just to say Accuspark were lovely, replaced my electronic bit despite out of warranty based on fact it had been in the box, new unused, for a year. I've bought their carbon leads - they are 12 quid...

I'm looking forward to plugging it all in again.

I must admit, for leads which cost just over a tenner, it seems a bit odd that Accuspark don't require that they are used for warranty, when they are saying that it's inadvisable to use copper. I appreciate that others have found copper completely fine, but we know that these units ARE very reasonably priced and as Stuart says, if it minimises risk on things which are naturally going to be a little less robust than oem...

[JonE]

Further to last, to avoid your unit frazzling, check the depths of your 5 brass inserts on the TOP of the accuspark distributor cap.
I've just realised one of mine is far deeper and had scorch marks... the acorns had given good connection except with this one, which wouldn't have been obviously evident dealing with new kit.

The silicone leads dont come out with the brass pins to stuff down the centre of the lead when fitting an acorn, but I think they do need something (a bit of copper wire fine?) as the centre stuff is too fragile [for friction clamp between a brass disc and the brass base] for more than a couple of doings up/openings when one faffs...