Lotus Elan

Mystery breakdown

PostPost by: paddy » Sun Oct 28, 2018 10:50 pm

For the first time in my ownership (not counting running out of fuel ...) the Elan failed to get me home. Luckily I was about 30 yards from home :)

The engine died when idling and wouldn't restart. I was at normal working temperature. Restart attempts would sometimes result in the engine just turning over, but most often one cylinder would fire once before dying as soon as the bendix had disengaged. After pushing the car home, allowing it to cool down, it was just the same. That was a week ago.

In the 10 minutes before it died it was hesitating under heavy acceleration. The hesitation would come and go - it was "binary" (ie either the hesitation was there or it wasn't) and it didn't feel like the kind of hesitation you get with fuel starvation which in my experience comes in progressively as you increase the demand and is uneven even under steady demand. So I'd been thinking that was probably more likely ignition-related. At low-medium revs everything felt completely normal.

Today, I charged the battery, fiddled with the LT and HT leads and found nothing wrong, took off the distributor cap and replaced it, and it started first time with seemingly no ill-effects. It idled well, timing was rock-solid on the strobe. I took the covers of the carbs and everything looked clean, nothing obviously wrong with fuel levels.

The ignition is an Aldon TC103 distributor with Aldon ignitor, magnecor leads and there is also an aftermarket rev limiter (this kind of thing: http://www.burtonpower.com/rev-limiter- ... exrlt.html).

Now that it's running fine I'm not sure how I can diagnose the problem. Any ideas? What spares do I bring with me next time I'm out? I have a spare distributor with conventional points so I'm tempted to fit that and/or a coil, or perhaps just disconnect the rev limiter because that has to be something to be suspicious of.

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PostPost by: wotsisname » Sun Oct 28, 2018 10:57 pm

I would be inclined to not rule out anything (eg fuel).. checking filters,etc... If it's now working it's hard to know if anything you change was the original issue. Not sure this helps much.. the intermittent issues are probably the worst
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PostPost by: USA64 » Mon Oct 29, 2018 12:20 am

I'd take a hard look at the battery.
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PostPost by: paddy » Mon Oct 29, 2018 12:36 am

USA64 wrote:I'd take a hard look at the battery.


That's an interesting comment. It's not been holding charge as well recently, and I can understand how you could have problems at idle with a low battery voltage and low alternator voltage. But at higher revs you'd expect to have the full ~15v alternator voltage, so how would that give the symptoms I had?

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PostPost by: Andy8421 » Mon Oct 29, 2018 7:14 am

While its a bit of an old saw, the expression 'most carburettor problems are electrical' seems to hold good with Elans.

I have had a spate of distributor cap and rotor arm problems that were temperature sensitive. The car ran fine for a while, would start to misfire under load, then would peg out. Only after it had cooled completely (up to an hour) would it start again - for the same problem to recur.

I swapped multiple new caps and rotor arms, only to establish that the usual suspects all seemed to source their components in the same place, and I was swapping one dud for another. I eventually obtained a new cap and rotor arm from The Distributor Doctor, who I could highly recommend for good quality ignition parts.

To add to your problems, I am afraid a duff coil could also exhibit similar symptoms, and your 'Ignitor' or rev limiter could also be playing up.

Assuming the problem is repeatable, I would drive it until it packed up, then trace my way through the ignition system. Check for a decent voltage to the ignitor leads (which may just be connected across the coil) as you crank the engine, pulses on the low voltage lead from the ignitor to the coil, a spark from the coil HT lead, sparks from the plug leads. The point at which things stop would indicate where the problem lay. Failing this, if you have access to substitutes, you can swap one component at a time until the problem goes away.

If the above doesn't appeal, then my first step would be to buy a decent cap and rotor arm from the Doctor, and if that doesn't make the problem go away, I would disconnect the rev limiter and see if that fixes it. If the problem still exists, then I am afraid you will have to have a go at the step by step diagnosis or substitution approach.

Edit: I have a vague recollection that the Ignitor relies on the base plate in the distributor for its earth. Might be worth checking the screws are tight.
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PostPost by: Mick6186 » Mon Oct 29, 2018 8:24 am

From past experience I have found that ignition problems cause the rev counter to become erratic or fail completely whereas with fuel problems the rev counter isn't affected so always watch the rev counter if misfire or engine cut occurs.
I would go back to points and a different coil and take off the rev limiter to narrow down the fault.
Another possible cause is low battery voltage. Solid state electronics just stop working if supply voltage goes below their low volt threshold,
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PostPost by: Elanintheforest » Mon Oct 29, 2018 8:26 am

I agree with Andy about the electrical bits being very suspect, and would replace your setup with a set of ignition parts, including coil, from the Distributor Doctor.

I had an Alden Ignitor setup fail in my Twincam Escort, and it was as if the ignition had been switched off. The car was recovered home, and to my surprise, it started the next day, but failed again after 10 minutes. And it wasn't the coil!

Alden are probably the best aftermarket systems available, and many will say they've had no problem with them. But if they do go, there is absolutely nothing you can do about it. A traditional system with good quality components should never fail, but if it does, it can usually be fixed, and most times gives warning of the impending doom!

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PostPost by: richardcox_lotus » Mon Oct 29, 2018 8:55 am

My 1st port of call would be the coil....just based on experience.

So worth carrying one of those with you !

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PostPost by: LaikaTheDog » Mon Oct 29, 2018 12:12 pm

Overheating coil. I upgraded to an aldon flamethrower when I had a similar problem.
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PostPost by: paddy » Mon Oct 29, 2018 1:51 pm

Thanks for all the replies.

I had thought about possibility of the coil overheating but had discounted it initially because it was a cold day and I'd not been far, so this was by no means an extreme event in comparison with other recent use.

The coil is a flamethrower from memory, but also 10 years old.

On Aldon vs conventional points: the Aldon components are 10 years old now and I'd originally fitted them with the aim of lowering maintenance (especially given the awkwardness of getting to the points) and reliability (given what seems to be the situation now for the quality of points and condensor). But it's definitely true that you can always get conventional points going again, and if you're not getting ultimate reliability from the electronic components than you can still end up on a recovery truck.

On the battery point - this is interesting because I was already finding that the battery would be too low to turn things over after a week of being idle. I will check whether or not there is any residual drain on the battery with everything turned off but I suspect it's just that it's no longer holding its charge. Today I checked the charging voltage and it's around 13.8V at ~3000 RPM without any other load which I think is too low. So my first step is going to be to check that out and/or replace the alternator, and possibly replace the battery unless it seems to have returned to normal after replacing the alternator.

Re fuel - I did check the filters above the needle valves and everything there was spotless so I'm going with the ignition theory for now.

Thanks again and I'll keep you posted.

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PostPost by: USA64 » Mon Oct 29, 2018 7:02 pm

KISS You already know it's a duff battery; change that before you tiddle with anything else.
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PostPost by: paddy » Mon Oct 29, 2018 7:18 pm

USA64 wrote:KISS You already know it's a duff battery; change that before you tiddle with anything else.


:) fair enough

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PostPost by: paddy » Mon Aug 26, 2019 7:54 pm

So in yesterday's heat I had the same issue. First stuttering at high revs, then just cut out. After leaving it to cool with the bonnet open for 5 minutes it was ok to run again.

I did manage to confirm that it's not down to the rev limiter, by disconnecting it.

So today I ordered a new coil, and reverted to conventional points. The alternator was replaced a while back. So hopefully now I can exclude anything ignition-related from any future occurrence.

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PostPost by: miked » Mon Aug 26, 2019 10:00 pm

I had a problem like this on my Stromberg Elan years back. I was killing dizzy caps with a flame thrower coil. I don't know what dizzy you are running (see it is tc103 after re read) but from memory the SAE spec for the 23d4 cap was under 30kv. I believe the coil voltage of the flame thrower is well in excces of this. I had a boot full of bad caps. Same symptoms.
In the end i went back to a standard lower voltage coil and then onto 43d dizzies as they have better electrical clearance and insulation withstand on their larger cap.
Lots of cheap crap 23d4 caps out there.
Last edited by miked on Tue Aug 27, 2019 8:25 pm, edited 1 time in total.
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PostPost by: Slowtus » Mon Aug 26, 2019 10:35 pm

USA64 wrote:I'd take a hard look at the battery.


? I have run cars with a completely dead battery, I have run cars on alternator alone, I have run cars with a dead alternator using only the battery to get me home/garage/pub.

I have run cars with every possible combination of the above.

Unless the OP has some lights telling him the charging system and/or its related components are giving a problem why would he question the health of the battery?

Genuine question, not a criticism.
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