Lotus Elan

Strange strobe

PostPost by: Mick6186 » Sun Jan 08, 2017 5:57 pm

Hi,
My 130/5 was fitted with a petronix ignition system, and when starting from dead cold the engine would be really troublesome, only firing on two then three cylinders until warmed up. I decided to go back to basics and fitted points( heavy duty cooper 'S') and condenser. This dramatically improved the starting and running from cold but. I decided to set the timing with my inductive pick up strobe lamp but I am getting no signal from plugs 1 & 2, but 3 & 4 are ok. The car is fitted with a new distributor cap and copper core plug leads. The engine is running on all four cylinders, verified by pulling of the plug caps.
Any ideas would be gratefully received,
Mick
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PostPost by: tesprit » Sun Jan 08, 2017 6:30 pm

What you are describing is certainly odd. If the engine is running on all four cylinders, it must have ignition to all of the spark plugs so that would lead me to think something has gone wrong with your timing strobe or its inductive pick up lead. Do you have another timing strobe you could try or know of someone that has a good one one you could borrow?

Dan
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PostPost by: Mick6186 » Sun Jan 08, 2017 6:45 pm

Dan,
I agree that the finger of suspicion points at the strobe but it works fine on two of the leads and the coil HT output. All the leads are new as are the plugs , which are all gapped at 22 thou. Most strange,
Mick
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PostPost by: Elanman99 » Sun Jan 08, 2017 8:58 pm

Electronic ignition is most commonly fitted to classic cars as an improvement. If nothing else it should perform as well as a conventional setup so it seems odd that going back to points cured a problem.

I suspect that whilst the points are new and correctly timed etc its somehow masking your original fault. I think I would be systematically checking all the ignition components, like measuring the resistance of the HT leads and observing the running engine in darkness to see if there is any tracking visible.

A correctly wired Pertronix (Aldon) should be really trouble free.

Ian
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PostPost by: john.p.clegg » Mon Jan 09, 2017 6:56 am

Mick
I take it you know the pick-up is directional?

John :wink:
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PostPost by: Elanman99 » Mon Jan 09, 2017 7:13 am

The purpose of the strobe light is to view and set the ignition timing so why do you need to trigger the strobe from any lead other than the one to number 1 cylinder?

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PostPost by: denicholls2 » Mon Jan 09, 2017 2:01 pm

Elanman99 wrote:The purpose of the strobe light is to view and set the ignition timing so why do you need to trigger the strobe from any lead other than the one to number 1 cylinder?

Ian


I believe he was looking for hints as to the original fault (and found them). I suspect that the spark from the Ignitor is not as hot as a spark from points (no reason for it to be, and would cause more radio interference, so likely designed that way.) However, when pushed through bad plug wires it could make a large difference. If they fit, I'd swap (both ends, please!) the plug wires between those with signal and without, which should definitively tell you it's time to replace the set.
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PostPost by: Chancer » Mon Jan 09, 2017 7:39 pm

I often had that problem with my strobe when I used it often, it had an Arrow for the direction which didnt seem to make much difference, the hook of the clamp had carbon material Inside which was broken in two pi?ces and I put it down to that.

I have a simple analogue Gunsons sparktester which creates a second spark gap in series with the plug which can gradually be opened until you know the maximum the leads will pass, checking all 4 leads with that showed they were all good despite the petulant strobe pick up.

On of dem tings innit!
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PostPost by: Mick6186 » Tue Jan 10, 2017 7:12 pm

Thanks for the replies.
The plug leads are brand new solid copper cored. The plug caps are new NGK.
The strobe only works on plugs 2&3 but I need it to work on number 1 to set the advance . The car starts much better from cold with the points and runs smoothly when warmed up. The strobe inductive pickup is in the correct orientation. I will continue with my investigations,
Mick
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PostPost by: oldchieft » Tue Jan 10, 2017 7:34 pm

The voltage at the plug would depend on the gap and the compression pressures.

If the pickup is not seeing a voltage opening the plug gap up might up the voltage to be detected?

Might be worth a try?

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PostPost by: Mick6186 » Fri Jan 13, 2017 6:01 pm

Jon,
You were spot on. I opened the plug gap from 22 thou to 35 thou and no change. However when I pulled the plug cap off so I could hear a spark but the engine still ran on 4 the strobe worked perfectly . All I can think is no. 1 plug isn't drawing the same HT as the others. With the strobe working I found that my static setting obtained with a light bulb was only 4.5 degrees advance. When set at 10 degrees the engine (1700 tall block with L14 cams and bigger valves) is running much smoother at idle with instant throttle response. Thanks Jon and all others for suggestions,
Mick
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PostPost by: Elanman99 » Fri Jan 13, 2017 6:21 pm

Mick

Glad its sorted, question now is, are you going to reinstate the electronic ignition?

Ian
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PostPost by: Mick6186 » Fri Jan 13, 2017 7:28 pm

Ian,
Good question!!
I think the electronic ignition will go back in the near future to see if the cold start problems return.
I trust points due to many years ago running a road rally 1275 Cooper 'S' with points which never let me down and would do many miles between checks. Do you know if the standard twincam points are 32oz, which I have fitted.
I originally fitted the electronic ignition because I didn't like the idea of the spark from the breaking contacts in such a high risk fuel area under the carbs, but I should imagine there must be plenty of sparks from the rotor arm as it transfers the HT to the distributor cap contacts. I am currently thinking of ways of making the distributor cap liquid and vapour proof to put my mind at rest,
Mick
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PostPost by: Elanman99 » Fri Jan 13, 2017 8:15 pm

The possibility of the CB points causing a fire is diminishingly small so to me its not a reason to go electronic.

A long time ago I spent a day at a mine safety establishment where all forms of experiments and demonstrations were carried out, from memory petrol was quite hard to ignite accidentally and I think the atmospheric conditions inside the distributor are never likely to be suitable for unwanted ignition.

I've no idea what spring pressure the points work at (in spite of running a 1275 Cooper 'S' in the day, supercharged too!). I made my own optically triggered CDI. Even though the Mini distributor was extremely accessible, eliminating the points saved having to regularly adjust or replace them. Access alone is a good enough reason to change on the Elan but better starting, sometimes from a really low battery voltage is enough for me.

Ian (now with an Aldon Ignitor)
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PostPost by: Chancer » Fri Jan 13, 2017 11:01 pm

You only need a minor fuel leak from twin 40's over a Dizzy on a warm or hot engine to pretty much guarantee a fire, been there done that too many times. Also spent too many years looking at burnt out chassis in breakers yard with charred bits of fibre glass poking out from the body mounting sandwich plates or bobbins playing guess the vehicle :D

Its probably the HT spark from the rotor that does the business though before the points get a look in, the condensor would normally reduce arcing to a negligible amount.

Distributorless ignition with Zetec type coil packs mounted high is the safest way to go.
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