morris minor woes

[Lyn_Lancaster]

Hi all
I am looking for some help with morris minor 1971 Traveller,
its a 1098 engine
electronic ignition
it was running fine last week but today as I took it out on a run the car started to misfire I believe certainly not firing correctly and progressing above forty as un-driveable
I have taken out all the plugs there is no fouling and look like a nice biscuit colour
the plug leads are fairly new along side the new electronic distributor all are connected I re checked the coil is an high powered one recommended for the electronic system. I cant see any thing obvious ,
there is a bit of tappet noise but only on one valve rear not sure if that would cause the rough running

I cant see any thing obvious and suggestions what I can look for or next steps

thanks
Linda

[svenedin]

Basically it is likely to be either fuel related or ignition related so we need to narrow down where the problem lies.

Does it sound rough and misfire just idling?

With the plugs looking a good colour it points away from a fuel issue but does not rule it out. Even with quite short periods of fuel starvation the plugs look pale. I had sudden onset of very rough running some time ago and it was related to a leak on the induction side (air being drawn in making the fuel mixture weak). This showed as pale looking spark plugs even though the engine was only run for a short time.

It sounds more like an ignition issue. I would go through checking things. Take the distributor cap off and check the rotor looks ok. Check the electronic module looks ok and the wires to the module have not been chafed and damaged. Check electrical connections to coil are clean and tight. Check the king lead from distributor to coil is tight.

To diagnose further if no fault found so far, get some of the neon spark plug testers and observe the spark with the engine running. It is costly to replace parts on a guess and much better to identify the problem accurately.

Ignition coils are notoriously unreliable these days so that is a suspect as is the electronic ignition module.

Check the carburettor dashpot has oil.

Another little test, when running rough does giving come choke make it better?

Stephen