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Exasperated by stuttering SP250... all suggestions welcome!

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Joined: Tue May 21, 2019 4:07 pm
Location: Thames Valley

Re: Exasperated by stuttering SP250... all suggestions welcome!

Post by Agnello11 »

Well, I'm back.... grubby and weary... but triumphant! :D

Much further tinkering and elimination of components left the finger of blame pointing squarely at the electronic ignition unit, as I had begun to suspect..... Consequently I went through the faff of reverting to an original points and condenser set up - not an easy swap as it required another distributor base plate, it's original having been modified to take an optical electronic ignition set up in the past....
Anyway, with points back in, the advance weights checked and the distributor back together it fired right up and sounded.... fabulous! A road test along the exact same route as all previous tests resulted in NO ill-running and it runs like a dream.... at long last... yay!!

When I think of the years it has taken to finally eliminate this.... and good old points were the solution all along....

You may well wonder why on earth it has taken so long and why the finger of blame didn't immediately point to the electronic ignition from the outset? Because it wasn't changed directly from points. If it had been, I think the problem would have been immediately obvious. The electronic ignition was fitted to replace a different electronic ignition system that was itself failing.... We knew the first Lumenition system had failed and it presented with very similar symptoms but cooked coils as well. The chances of replacing a failing electronic ignition system with a brand new, but faulty, different brand electronic ignition system that produced very similar symptoms must be in the millions to one. As a result, the true source of the running issues was well disguised and we began to suspect that there was something else amiss beyond the original failing Lumenition system. Being unreliable and untrustworthy, the Dart wasn't used very much so it never made it to the top of the job list to undertake a thorough end-to-end investigation..... Knowing that points couldn't simply be refitted without sourcing another top plate for the distributor and the fact that the latest failed electronic ignition presented no symptoms when cold and continued to fire a big fat spark all along hasn't helped.

Still, it's been an interesting journey and I am most appreciative of all the input every one of the contributors to this thread has taken the trouble to provide - it has been enormously helpful and many lessons have been learned, not least in failure analysis and the importance or revisiting the last component touched FIRST....! :shock:

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Re: Exasperated by stuttering SP250... all suggestions welcome!

Post by John-B »

Congratulations! :D and commiserations that it took so long. You ought to be awarded the "Order of the Original Points" or something. Now enjoy the summer and go to as many shows as you can.

This isn't the first time that someone has had problems with electronic ignition and in most cases managed to revert to points at the roadside. Why is electronic ignition so prone to problems and is any particular brand more likely to fail? The manufacturers should receive feedback from you - both of them.

What exactly would be the cause - coding in the microchip? It seems strange that a car should run well when cold and then suddenly run badly when hot. Is temperature encoded into the chip, or is it a time-related factor?

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Re: Exasperated by stuttering SP250... all suggestions welcome!

Post by Sydsmith »

That is great news Larry and as John says you deserve a putty medal for persistence.

There is an old adage "simple is best" and though many satisfied customers will point to the advantages of electronic ignition, fitting them retrospectively is a risk. Electronics only belong in a car when they are integrally designed to be there, but even then, as some of us know to our cost, electronics in a modern car are just as much a menace.

My first V8 250 had electronic ignition, it was a pest, I never knew if it was working properly, It was never easy to check, even though I am a qualified TV engineer, I could never just twitch the contacts and check for a spark, sooner or later it had to go.

An original V8 ignition system has a dozen or so components to go wrong an electronic system has 100's. Need I say more.

Great to hear that you are sorted. Syd

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Re: Exasperated by stuttering SP250... all suggestions welcome!

Post by Big Col »

Really pleased you have got to the bottom of it. An SP that can’t be enjoyed is a true travesty of justice.
I may be slow but I’m rough as well !

Warsash 2
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Re: Exasperated by stuttering SP250... all suggestions welcome!

Post by Warsash 2 »

I have followed this with interest although my symptoms were the reverse in that it initially coughed and spluttered when first starting for a couple of miles. On the way to the International rally it got progressively worse. The sages at the International suggested all sought of things but having read your post and I was carrying a refurbished distributor, by the Distributor doctor to the original spec I was helped with switch. When the non electronic system was fitted the car ran very well. now I am home it just needs a bit of adjustment to the timing for it to run perfectly. The system fitted was a Lumination which I have had on my V8 250 for a number of years and runs perfectly. The SP is still +ve earth and I wonder if the electronic systems do not like the earthing arrangement. Every time we take the SP to Scotland we have a problem but we have toured Europe with only minor problems. Funny that!


Ian Slade
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Re: Exasperated by stuttering SP250... all suggestions welcome!

Post by Ian Slade »

I know it's not standard but as so much electronics today are for -ve earth cars it must be worth swapping to -ve earth, on most SP's it is just turn the battery round swap the Ammeter connections and replace the leads , unless you have an alternator and a +ve earth radio that's it, the dynamo will still charge and the starter still work.
Owner since the 70's, Genghis is slightly to my left.

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Re: Exasperated by stuttering SP250... all suggestions welcome!

Post by timmartin »

I suspect that the above references to earthing may have a point.

My SP came to me (13 years ago) with a much abused and badly installed Lumenition optronic system.
It still has the same unit, and runs very well, about 4k miles a year.

But, During the first year of ownership, the car had become really horrid to drive after 20 or 30 minutes from cold. It could be kept going at speed albeit with some loss of power, but was a real pig at low speed. Quite difficult to drive in traffic. It was not overheating.

Leaving out the long story, I reinstalled the same Lumenition unit in a new location (near to the coil for convenience) and made a nice job of the wiring. Most significantly, I installed a really good earth to the unit itself.

Problem gone, perfection!
Blue 1964 SP250 in Berkshire

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Re: Exasperated by stuttering SP250... all suggestions welcome!

Post by Agnello11 »

Earths was one of the things we attended to. A time-served sparks tipped me off many years ago that 90% of electrical problems (wherever) were generally down to poor earths... We added additional and renewed where necessary to ensure there was a properly good earth from the battery.
I had also gleaned that it was not recommended to retain the same electronic ignition system when changing from +ve to -ve earth, so when we made the decision to upgrade to a dynamator (alternator in a dynamo body) and switch to -ve earth, part of the conversion we elected to undertake included removing the Lumenition system (which we already knew was proving troublesome) and changing that for a more modern 'reliable' magnetic system.

Ironic that the purportedly reliable magnetic system was the problem. Despite being initially helpful in the problem-solving phase, the company that supplied the electronic ignition system have let themselves down in customer service terms now that the fault has been proven to have originated in their system..... 'suck it up' is very much the message received.... Disappointing given that their system didn't work from the outset and the amount of time and energy (not to mention money!) we've had to devote to tracing it.... such is life though. Voting with feet and £££ being the only long-term recourse against such 'service'.

On a happier note the Dart is running like a champ. It sounds magnificent and goes every bit as well as it sounds... really a pleasure to drive. The happy note has inspired some titivation of a couple of other minor areas that had been neglected and it now looks as magnificent as it sounds too, so this story has a very happy ending....

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