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Ignition Problem


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Hi Guys,

My 1984 S3 Turbo has suddenly decided not to produce a spark at the plug.

The car has always started up instantly and has run perfectly for years, but last week it started to splutter under load and became difficult to start, once started, it would rev freely stationary, but again, once driven as I reached approx 4000rpm, it would misfire and gain no further power.

I ran a few obvious checks,but everything looked fine. I then checked out the ignition side of things, and discovered only a weak spark was being generated at the end of the coil lead, but when connect back to the dizzy there was no spark at all at the spark plugs.

The Magnecor performance HT leads are only a couple of years (or 4000 odd miles old) as is the spark plugs,battery,dizzy cap, Rotor arm, Pick up in the dizzy and the lead from the pick up that goes to the Ignition amplifier, that leaves only the coil or the Lucas AB14 Ignition Amplifier as potential component suspects.

Steve from SJ Sportscars says its highly unlikely to be the Ignition Amp as he has never known one fail in his 30 years Lotus experience.

The symptons have presented themselves as a component gradually breaking down, as opposed to instant failure.

Im guessing then, my instinct says the coil, but If anyone could help with any suggestions to this annoying problem I would be most grateful.

Kind Regards.

Iain Nicholson.

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  • Gold FFM

I'd definitely be going for coil first. You can do some simple primary/secondary resistance tests to give a good indication of its condition. Likewise, I don't think I've ever changed an amp in one of these distributors.

Also, make sure you have a good engine earth!

British Fart to Florida, Nude to New York, Dunce to Denmark, Numpty to Newfoundland.  And Shitfaced Silly Sod to Sweden.

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Hi Guys,

Bought new coil but still no spark!!! GRRRRR..........There is voltage to the coil, I have confirmed this by carrying out a simple bulb test, however the bulb only lights if I place contact between the positive or neg terminal on the coil and the coil body itself, it doesnt light if I place contact between the pos and neg terminals on the coil. Would I still get some sort of weak spark at the end of the coil HT lead even if the ignition amp has failed? Where else can i look for clues?

Iain

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Now most points driven coils work by giving a spark at the moment the circuit is broken and the magnetic field dissipates, I'm not sure if that is still the case with the Lucas amp system. I'm trying to think of a reason why it wouldn't be, and can't so have to assume it's normal operation simply driven by the amp.

You may be better off trying a multimeter in series with the coil and look for current flow (should only be 1/4 amp).

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The workshop manual gives a very detailed troubleshooting procedure.

I used it to work out what was wrong with my '84!....and it was right, wiring to the distributor in my case.

  • Like 1

Robert Costa
1984 Turbo Esprit
Very Black!
2004 Lotus Elise
Quite Green! gone 😞

1977 S1 Esprit, in less bits

1998 Lotus Elise S1, Azure Blue
Sydney, Australia

“The car's weakest part is the nut holding the steering wheel”

Recommended procedure before taking on a repair of Lucas equipment: Check the position of the stars,kill a chicken and walk three times clockwise around your car chanting:" Oh mighty Prince of Darkness protect your unworthy servant.."

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If it's one of the Lucas systems with a 3 way connector in the lead to the distributor...that would be my first suspicion. They corrode and go intermittent. Often a bit of a wiggle and it all bursts back into life! Try cleaning the contacts.....

Scientists investigate that which already is; Engineers create that which has never been." - Albert Einstein

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Hi All.

Fitted a brand new Ignition Amplifier inside the Lucas AB14 box as another possible culprit to this frustrating problem, (only £20.00 from a very helpfull motor factors,) Guess what?? still no spark!!! As I have either replaced or checked every part of the ignition system, I am now running out of ideas what to check.

Maybe the Meta M36T Immobiliser fitted to the car could be at fault? it appears to be working ok, as the car engine wont turn over until the normal sequence of inserting the fob into the fob slot and the flashing red LED extinguishes. but there is a fine red wire that goes to the negative terminal of the coil, and a braided uninsulated earth lead that terminates at the coil mounting plate these wires are in the wiring loom that goes into the coil box, but these wires dont appear to be illustrated in my workshop manual wiring diagram!!

According to the manual there are 2 wires from the ignition amplifier to the coil, (white, and white with a slate line) and the same colour wires from the wiring loom to the coil,but no mention of this red wire and earth wire.

Could these wires be part of a circuit that has broken down from the immobiliser? Or are they present on all 1984 Esprit Turbo's?

Just exploring all crazy avenues :-(

Iain

Edited by iain Nicholson
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  • Gold FFM

You checked the earth?

Also, do you know for sure that the distributor shaft is turning? Maybe the dizzy has migrated out a bit...

British Fart to Florida, Nude to New York, Dunce to Denmark, Numpty to Newfoundland.  And Shitfaced Silly Sod to Sweden.

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  • 5 months later...
  • Gold FFM

Hi, I had similar problems the other week, first the sheilded wire with the Red thin wire is for the rev counter as already suggested, I also found that someone in the past had removed the black earth wire from inside the distributor, with theLuminition system this should be left in place, other info passed to me at the time was as suggested remove the wires from therev limiter off as the car will run ok without it, I also fitted a sumplimentary earth from the module to one of the mounting bolts for the starter solenoid, this in conjunction with cleaning all the other earths made a vast improvement but unlike all other suggestion I did in fact have a faulty ignition module I also found again as suggested a lot of crud on the 3 wire plug going to the dizzy, I cleaned and replaced as above and now she starts first turn of the key, hope this helps.

John.

:wallbash:

Edited by johnpwalsh
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