Failure to fire on all cylinders after driving a distance

[Jamesjmercer]

I'd welcome some thoughts on the following (intermittent but persistent) problem.

I have a 1960 Convertible with its original (although at some time rebuilt) 948cc engine.

The engine starts every time and runs smoothly.

However after 20 or so miles (regardless, it seems of traffic conditions) it will lose power and fail to fire on all cylinders.

Usually, by putting my foot hard on the accelerator I can 'power' through it. Recently however the engine stalled completely.

The problem can be exacerbated by stopping, say at a pedestrian crossing and then pulling away. The power is not there.
On a restart from either hot or cold, the problem appears to vanish - at least for another 20 miles or so....

I do not think there is a problem with the head gasket. The radiator water level is not dropping. There is no moisture obvious in the exhaust. Compression is fine on all cylinders. There is a good spark at the plugs. The carburettor is clean and does not appear to be sticking.

The engine has been serviced within the last three months (the problem was not evident prior to the service however...)

Any thoughts?

Thanks

James

[lowride stepside]

valve clearances could be way too tight , 20 miles sounds too far for fuel starvation

[bmcecosse]

Change the condenser....it may be knackered and overheating..... Could also be very small points gap I suppose...reset to 15 thou.

[simmitc]

Find out what was replaced at the service, and put the original bit back! Agree that condenser is most likely, followed by rotor arm.

[kennatt]

dare I suggest swaping the coil, ahhh here he comes

[David53]

It sounds a bit like a fuel vaporisation issue, but if it only started after the service that's probably not going to be it. Certainly something getting hot and causing the problem.

[bmcecosse]

It's NOT the coil......NEVER is !! It could be a vacuum developing in the fuel tank - if no air can get in. When it stops - is the fuel pump heard hammering away?

[liammonty]

I've had two failed coils in recent years with similar symptoms to what you describe. It's a fact of life that the modern coils are junk, even 'Lucas' branded (mine failed after just 12 months). Don't rule the coil out, especially if it's not the condensor, points etc.

[bmcecosse]

My comment (as ever) applies to original coils - which never fail, and last 'for ever' unless physically damaged of course. Much of the time - replacement coils are incorrectly specified which speeds their demise..... Avoid!

[liammonty]

I agree, but the trouble is, a lot of cars out there have got new coils on now, and some owners may not even know... Also, it's. harder to pick up old ones now. Luckily I had a stash. I heard that many new coils have insufficient windings in them which is why they fail, even though they claim to be correct spec. Just rubbish I'm afraid...

[bmcecosse]

Here's one... http://www.ebay.co.uk/itm/12v-Lucas-ign ... 1e80f09892 and another.. http://www.ebay.co.uk/itm/Cortina-MK1-I ... 2583bb2947 Fill your pockets...many more listed...

[JOWETTJAVELIN]

Just watch out for the king lead connection as some push-in, others screw-in. Obviously this makes a difference to the running of the car if you don't know you've fitted the wrong type.