Stops when hot! Why?

[seaandmoor]

Hi all,
Elan +2 1973
It has been running really during the cold weather.
However, over the last few weeks whilst it has been this glorious weather I find that it will run for 20 miles and then go very rough and have to stop. Let it cool down and it's fine..... for another 20 miles.
I've changed plugs, leads, cap, rotor arm - needing changing anyway but no difference.
Any ideas as to what might be the problem and what should I check for next please?
Thanks.

[bill308]

seaandmoor,

A failing coil is a possibility.

Bill

[elansprint71]

Condenser? They sometimes don't work when hot.

[Elanman99]

My money is on the possibility that the fuel tank vent is blocked. (the filler cap should have a small air hole somewhere)

If there is no tank ventilation, it gets harder and harder for the fuel pump to extract the fuel. Progressively poor engine performance until the engine eventually stops. In my case, in the middle of knowhere on a dark country lane, the young lady passenger of course thinks that this is all part of the plan!

Ian P

[Robbie693]

My money is on the possibility that the fuel tank vent is blocked. (the filler cap should have a small air hole somewhere)

If there is no tank ventilation, it gets harder and harder for the fuel pump to extract the fuel. Progressively poor engine performance until the engine eventually stops. In my case, in the middle of knowhere on a dark country lane, the young lady passenger of course thinks that this is all part of the plan!

Ian P

Don't know about the Elan but on a Plus 2 the cap is not vented - the breather pipes do the venting. With a vented cap you get petrol streaming down the wing on right hand bends. Worth checking the breather pipes though

Robbie

[worzel]

Hi

Immobiliser fitted? Does it stop after a set period of time rather than distance?. Only asked because when I had a Cat 1 immobiliser fitted the electrician wired it into the ignition circuit- they're not designed to have current running thru thwem continuously- only discovered this after a lot of searching. My car used to stop after around 30 minutes running- leave it for around an hour and everything back to normal.

regards

john

[andyelan]

Hi Seaandmoor

I would say this is almost certainly the coil breaking down when it gets hot. Between my 2 cars I've had to replace three of these (all branded items) in the last 5 years all becaues of the exact same symptoms. However, do change the condenser too while you're at it, the ones available these days don't seem to be very good and don't last very long either.

Andy

[seaandmoor]

Replies from most of the regulars thanks. BMC Clarke is quiet - he must be away
Well I wondered about the breathers for the Plus 2 and forgot to mention that I did try it with the flip up filler cap unclipped but that didn't give an instant cure.
Also forgot to mention that the car has had a replacement lumenition capacitive discharge ignition system as the first lumention went with a puff of white smoke! It does of course still have the coil and capacitor.
I now remember replacing the capacitor on my old mini many years ago but my fathers lawnmower still has the same capacitor since 1960!
I'll see if I can swap coil and capacitor at the weekend and try that.
Many thanks to all for such prompt replies but if anyone has any other quirky advice let me have it in case the weekend comes and goes without solution.
Cheers.

[bast0n]

C and Moor

COIL - COIL - COIL!!!!!!!!!!!!!!

I have had three fail in hot weather, plus 35 and above - now have coil mounted above my feet in the cockpit, nice and cool, and no further problems. (Four years on and umpteem miles in V hot weather)

Don't grow up too quickly............

David

[Andy8421]

With the demise of Lucas, many of the pattern parts available for the ignition system seem to be of poor quality and either fail after a short period, or don't work at all (many would argue it wasn't much better when Lucas were still going)

I suffered exactly the symptoms you describe, and after a great deal of hassle traced it to the distributor cap - which became conductive when hot. I tried three or four caps from different suppliers, but all had been sourced from the same manufacturer, and all had the same problem. The tell tale sign was a small square moulding sprue on the top of the cap.

As others have pointed out, your problem could be coil, dizzy cap, condensor, rotor arm or leads. Any of these components can fail when hot, only to come back to life when they have cooled. The morale of my tale is if you are trying to find the fault by substitution, dont assume that new components are going to work any better than the originals, they could even be worse.

[seaandmoor]

Andy thanks for the depressing news on replacement parts! What is a 'sprue' that I should be looking for?
As for repositioning the coil away from the heat of the engine bay - well I hadn't thought of that. It's amazing what imaginative minds you lot have! I really must get out a bit more.
By the way I did change to Denson Iridium plugs at the end of last year and if anything the engine ran better - until this hot weather.
Thanks again for some good advice.

[Crusty]

I had the same prob . With the lumination i had a dog tacho reading so i changed it all back as it was in 1969 plugs points new coil and condenser runs the best since i got her and the tacho is great.
No more getting hot in traffic jams and conking out..

[Andy8421]

The caps in question were side entry, with push fit connectors.

A sprue is where the plastic entered the mould during manufacture. The main part of the sprue gets broken off, but a lump remains with the same profile as the sprue. If you looked down onto the top of the cap, the sprue was dead centre.

http://en.wikipedia.org/wiki/Sprue_(manufacturing)

[seaandmoor]

Ah 'sprue' - I understand now, thank you.
Yes I too had a problem with erratic tacho but sent it away to somewhere in South Wales and they did something so that it is now smooth and steady with the lumenition. Weather has taken turn for the worse so whether I'll get under the bonnet this weekend or not I'm not sure.
I am tempted to go down the mappable ECU/EDIS route with crank/O2/AFR sensors and AFM. I've another old car with this fitted afterwards which I can plug into a laptop and the difference is way out in another world. That's for another time though as I need to rely on a good auto electrician and it needs to be planned well in advance so that it can be done when the opportunity presents its self - like engine out! Realistically that might be never! But it is nice to muse on such things.

[Elanman99]

[quote="Andy8421"]The caps in question were side entry, with push fit connectors.

A sprue is where the plastic entered the mould during manufacture. The main part of the sprue gets broken off, but a lump remains with the same profile as the sprue. If you looked down onto the top of the cap, the sprue was dead centre.

http://en.wikipedia.org/wiki/Sprue_(manufacturing)[/quote]

Have I misunderstood something here? I thought the central sprung carbon brush was in the dead centre of the distributor cap, so making contact with the rotor arm.

Ian P