Lotus Elan

A Lotus moment.....

PostPost by: 2tmike » Mon Jul 20, 2020 12:18 pm

I'm a little baffled....yesterday the S4 did about 150 faultless and fun miles, in fact since completing restoration of the car the engine has never missed a beat. Then this morning after about 1/2 mile the engine cut completely at around 30mph. Totally dead, no response to the throttle. I pulled over and after a bit of cranking it burst back into life and again seems to be running perfectly. Fuel supply related perhaps ?
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PostPost by: wotsisname » Mon Jul 20, 2020 12:39 pm

I might be inclined to look at the anti-theft switch first, if you have one fitted.. sudden stop, rather than a spluttering halt, feels like electrical to me. possibly easier to check over than some of the more illusive fuel supply issues ?
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PostPost by: 2tmike » Mon Jul 20, 2020 1:17 pm

OK, I'll have a look. All wiring looms and things like the anti theft switch were replaced during the restoration. There's nothing worse than an intermittent fault.......
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PostPost by: MrBonus » Mon Jul 20, 2020 1:40 pm

I bought a 2012 Mustang Boss and it would intermittently cut all power to the car and engine when I hit a bump then miraculously fire back up again (while driving). Turns out, there was a loose ground (that could have conceivably created a fire).
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PostPost by: 2tmike » Mon Jul 20, 2020 1:46 pm

Pretty sure not, the switch checks out ok.
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PostPost by: 2tmike » Mon Jul 20, 2020 1:48 pm

I did all grounds carefully during the winter but there's no harm in another look.....
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PostPost by: ericbushby » Mon Jul 20, 2020 2:37 pm

Hi, May I suggest a different approach.
When static testing has failed to find anything the way to find intermittent faults is not to test for them, but to monitor them constantly and wait for it to happen again.
Run a wire from the 12 volt terminal on the coil through into the cabin and to a lamp laid on the passenger seat. Even out of the bonnet and in at the passenger window will do for a while.
Ideally the earth connection should come from the ignition circuit earth point which is probably the distributor body but any earth will do to start with.
Any, even momentary, interruption will be seen on the lamp.
Hope this helps
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PostPost by: 2tmike » Mon Jul 20, 2020 2:52 pm

Hi Eric, yes you may...:) I'll set this up in the week and see if it shows anything
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PostPost by: sprintsoft » Tue Jul 21, 2020 12:51 am

+1 for Eric’s approach, smart.

Maybe the movement of your ignition switch when trying to restart brought a loose connection back together. Did you replace the ignition switch during the restoration? Always well worth doing for peace of mind

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PostPost by: Bigbaldybloke » Tue Jul 21, 2020 10:37 pm

I had a similar problem years ago and ended up fitting a wire direct from the starter solenoid live via a spare switch direct to the coil instead of the harness wire. Obviously no rev counter but that was the least of my worries as the car would just randomly die on me. It still did it with this direct power feed so all that was left was the coil, distributor and electronic ignition. Finally nailed the fault to the optical pick up in the distributor for the electronic ignition, changed that and problem gone. Other possibility is blocked fuel tank breather but most Lotus’s have the opposite problem of trying to stop leaks around the filler so pretty unlikely.
Should mention that my car had a 12v coil fitted so direct supply was no problem.
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PostPost by: 2tmike » Wed Jul 22, 2020 7:05 am

Thanks guys for all the suggestions/ideas. I'm going for Eric's monitoring idea today, will probably use a test meter on the coil feed and a blast up Porlock hill - well, the sun's shining ...:))
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PostPost by: Andy8421 » Wed Jul 22, 2020 9:31 am

An easy test of the electrical low voltage ignition circuit in cases like this is to look at the rev counter just as the engine cuts out. If the rev counter drops to zero immediately, then you have a low voltage electrical problem. If the rev counter is still showing revs as the engine speed drops, then the low voltage ignition circuit (points, wiring, electrical supply to the coil) is probably OK and your issues are elsewhere.

You would expect a cough and a splutter before an engine died if it was fuel, a dead stop is usually electrical. When you rebuilt the car, did you source the ignition components from a reputable supplier like the 'Distributor Doctor'? There are still dud rotor arms, distributor caps and capacitors (condensers) in circulation from the usual suspects that fail under stress (mainly when hot) but miraculously come back to life when left for a few minutes.
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PostPost by: 2tmike » Wed Jul 22, 2020 10:16 am

I must confess to not noticing the rev counter as the whole thing took me completely by surprise, indicators, fuel gauge, and I think ignition warning lights were ok though, my main concern was finding a place to stop on a country road.....Its running a luminition system (proximity not optical) and in the 1000 or so miles I've done in it since ownership its run faultlessly. Its now equipped with a multimeter on the passenger seat linked to the coil so I'm off to give it a run and see what that brings.....
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PostPost by: 2tmike » Wed Jul 22, 2020 2:43 pm

Well I did a short run monitoring voltage to the coil and it was fairly steady , starting at about 12.5V at tickover and rising to 14.5-15V approx at a steady 3000RPM. Seems high? anyway no voltage dropouts but a misfire started to creep in around 2000rpm so I returned home. Later I went down the road to fill the tank and the misfire really got bad, throughout the rev range so back home again. It starts and idles perfectly but is approaching undrivable on the road. I'm thinking HT system and will get a new dizzy cap and rotor arm just to try, maybe a coil as well ?
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PostPost by: ericbushby » Wed Jul 22, 2020 6:55 pm

I call that a result.
You now know which direction to look in.
I would go for the cheap things first, such as spark plugs and rotor arm, maybe distributor cap.
If they prove not to be needed, they will be useful spares in the future.
Good luck, I think you are nearly there.
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