Lotus Elan

Engine runs erraticaly then dies

PostPost by: William2 » Mon Jul 17, 2017 4:46 pm

Having done about 700 trouble free miles on rebuilt engine I went out today (sunny about 82 degrees F) and the engine spluttered to a halt. I had gone about 10 miles and was stuck in a traffic jam for about 15 mins but engine temp was fine and all running/idling fine at about 85 degrees. The traffic cleared and having gone a further 3 miles the engine started to run more and more erratically and if you applied any accelelerator it would just not go above about 2000rpm and about 35mph. Luckily I was on a small B road as it gradually got worse and worse and wouldn't pick up at all. The engine died as good as so I pulled over and opened the bonnet. Nothing obvious, so I let it cool down for 5 minutes, managed to restart it and limped another 2 miles to home with the engine still not behaving.
The car is running a Powerspark ignition module in standard dizzy, new NGK 6ES plugs and an Accuspark Red Sports coil and red rotor arm (all new). Is it more likely to be an ignition problem than fuel. It is unlikely to be a blocked idle jet as the engine should still run on 3 cylinders. Until this happened the car has been running very well.
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PostPost by: EPA » Mon Jul 17, 2017 4:55 pm

I would check the plugs to see if they got fouled whilst in the traffic jam before looking elsewhere
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PostPost by: ericbushby » Mon Jul 17, 2017 5:01 pm

It won`t run on three cylinders without petrol !!
My first thought. When it is running rough is there still fuel in the float chambers at the correct level ? Then you can move on to ignition.
Eric in Burnley.
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PostPost by: tesprit » Mon Jul 17, 2017 5:16 pm

The key here could be "sunny about 82 degrees and stuck in a traffic jam" which leads me to suspect vapor lock in the fuel lines and/or boiling fuel in the float bowls due to excessive heat build up in the engine compartment. Have you had a chance to try starting/driving it again after letting the engine completely cool down?
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PostPost by: Chancer » Mon Jul 17, 2017 6:11 pm

Your first reflex whenever an engine splutters should be to look immediately at the rev counter.

Too late now of course but if it does it again.....................................

Sounds like ignition to me.
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PostPost by: Jentwistle3 » Mon Jul 17, 2017 9:49 pm

Is it charging? Sounds like ignition to me also, flat battery?
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PostPost by: William2 » Tue Jul 18, 2017 10:51 am

In answer to some of the helpful suggestions, yes it is charging fine and a new battery. I have not heard of vapour lock, is this a problem with Elans?? I have taken the plugs out and they all look ok and not unduly sooty. I have checked level of fuel in float chambers and that's ok. I have attached a photo showing position of my coil which is quite close to the rad but I thought a sensible position as opposed to under the airbox. If it were a problem with the coil breaking down due to excessive heat build up would it be an idea to wrap the coil body in some form of heat shield? I wonder if many others have had issues with stainless steel manifolds throwing out too much heat in the engine compartment. I guess I could try lagging some of the tubes you can access. I also wondered about cutting 2 holes out of the inner grp wheel arch area opposite the carb airbox similar to the ones on the exhaust side to try and let more air in.
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PostPost by: rgh0 » Tue Jul 18, 2017 10:56 am

I have positioned the coils in my Elan and Plus 2 in the same position for many years without issues.

The issue could be a problem with the pump and fuel when it gets hot and vapor locking or it could be a problem with an ignition component failing when it gets hot.

No easy diagnosis unfortunately.

Heat in general should not be the issue but a component or system not performing as intended when it gets into normal hot operating temperature range

cheers
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PostPost by: Elanconvert » Wed Jul 19, 2017 8:29 am

one of my sayings is 90% of fuel problems are electrical.....but then there is the 10%...
I wuld say from experience that if it was coil overheating, it would run ok once cooled down...are you using the right coil?
also I once bought a 'new' rotor arm which was faulty from the outset [modern far eastern one]........might be worth checking....mechanical fuel pumps wear and at low revs mght not push enough fuel through....

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PostPost by: William2 » Wed Jul 19, 2017 10:48 am

I have just had a chat with Powerspark about possible problems. I mentioned that I was using copper leads fitted with NGK supressed spark plug caps but nothing fitted between the ignition coil and dizzy cap. I was told that this could be the problem and that I should either fit a complete silicon lead set or at the very least fit an in-line resistive load in the coil lead. He said that it is possible it may have damaged the electronic ignition module. Very interesting.
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PostPost by: Foxie » Wed Jul 19, 2017 12:13 pm

William2 wrote:I have attached a photo showing position of my coil which is quite close to the rad but I thought a sensible position as opposed to under the airbox. If it were a problem with the coil breaking down due to excessive heat build up would it be an idea to wrap the coil body in some form of heat shield? I wonder if many others have had issues with stainless steel manifolds throwing out too much heat in the engine compartment. I guess I could try lagging some of the tubes you can access. I also wondered about cutting 2 holes out of the inner grp wheel arch area opposite the carb airbox similar to the ones on the exhaust side to try and let more air in.


Wlliam,
After 31 years of Lotusing, with the coil in the normal position at the airbox, I have never had a problem with a coil overheating. I do not believe your problem is coil related.

And wrapping the coil with heat shield would (a) only slightly delay its temp rising to local ambient temperature, and (b) prevent the dissipation of the heat normally produced by an operating coil. And I wouldn't be cutting holes in the wheel arch.

It is unlikely to be a blocked idle jet as the engine should still run on 3 cylinders. Until this happened the car has been running very well.


That doesn't follow. Check the carbs/adjustments completely.

To check whether the problem is engine compartment temperature related at all, have you tried driving around with the bonnet removed ? :)
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PostPost by: Davidb » Wed Jul 19, 2017 7:20 pm

I found this with a brief search:
lotus-electrical-f38/pertronix-ignitor-with-solid-core-leads-t25713.html

I am concerned now because I just fitted a Pertronix distributer with solid copper cored wires but have not test driven the car yet due to other work. It looks like I am going to have to change the new plug leads...

Edit:
I just found this--read down to the red writing at the bottom-rats!:
http://pertronix.com/prod/ig/ignitor2/default.aspx
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PostPost by: Robbie693 » Fri Jul 21, 2017 12:05 am

William - I had exactly the same problem and it turned out to be the Powerspark module had developed a fault. Simon kindly supplied me with a previously tested module to diagnose my problems with and as soon as I fitted it the problem went away. He also asked me the same questions about copper leads but I have a silicone set. I bought one of their dry coils at the same time as they are less prone to heat break down and so far everything has been fine. About 12 months now...
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PostPost by: William2 » Fri Jul 21, 2017 11:07 am

Hi Robbie, I have ordered a new Powerspark module in case mine has a fault which may have been caused by not fitting a 5K suppression resistor in the main coil HT lead. I measured the resistance of a length of silicon HT lead I had and it was about 4K. I believe I am correct in saying that if using copper leads, as long as you fit 5K NGK plug caps and the inline suppressor there shouldn't be any problem. If anything this combination offers more protection as the resistance is slightly higher than the silicon leads. I will let you know the result.
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PostPost by: William2 » Fri Aug 11, 2017 4:36 pm

Having fitted a new Powerspark module and double checked the ignition timing, both static and up to about 3000rpm with a strobe and all readings fine. I took the car for a run. Everything was running well for 25 miles of normal driving, not exceeding 50mph and no traffic jams. Water temp and oil pressure normal. Carbs are DHLA40s'. Then, as before, the car started running erratically and not pulling under acceleration and the idle was becoming worse and worse such that the engine wanted to die if you took your foot off the accelerator. I managed to limp home luckily. Whilst all this was going on I checked that the rev counter was behaving normally and it was.
I carried out a few tests in the driveway: opened fuel filler cap in case of pressure build up. Immediately fitted another coil. Opened the bonnet to help cool down the engine bay. None of these tests made any difference.
I noticed that if I revved the engine quickly up to about 4000rpm it popped a bit and I could hear some spitting within the airbox. The braided fuel pipes are warm to touch but not excessively so. Fuel pump is standard and rebuilt.
I am getting very frustrated with this problem and running out of ideas!! Any further help would be much appreciated. A friend on mine suggested fitting points and condenser to see if that made any difference.
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