Morris Minor Owners Club

I have slight misfire now and again on my Morris and having checked the usual suspects (but not the coil obviously ) it still happens every now and again, so want to put on new leads to the coil - the thin ones - but god knows if the thin ones presently connected are the correct gauge - so can somebody tell me what amp wire to use to make up new low tension leads?

Thank you

Low current - so 5 amp wire will be more than enough. It's very unlikely to be the problem.

You could easily do more harm than good by trying to change these cables. Unless the connectors are visibly loose on the cables, your new connectors are likely to be less well secured, especially if you use those nasty pre-insulated crimps, or use the wrong-sized connectors for the cable, or don't use a proper ratchet crimper to apply them.

I think a bit more investigation is required before you dive into the back of the ignition switch, or even the short cable from coil to distributor.

Kevin

I agree in part with the risks mentioned - however you are right to look for the cause of a miss-fire.

My first Minor developed a misfire- it continued for 9 months until it stopped completely on the M6 in busy traffic!
That one turned out to be the rotor arm (internal short through the Bakelite). My sister was running the car so I had replaced everything before handing the car over... it was the new rotor arm that caused it to fail. This was back in 91 and the rotor arm problems were well known over the next 10+ years until most of the stock had been sold through the supply chain...

One option (depending on the age of car) is that you may have multiple spade connections at the coil (or you can use spade connectors that have a male and female to allow both wires to be fitted).
If so, you can double-up the wiring rather than replace it - if this doesn't cure the misfire then you've not lost anything (apart from time) but have ruled out one part of the circuits.

Regarding miss-fires - most common is on the HT side. The higher voltage gives the current more chance to find an alternative path. On the 12v side don't forget to check it's not the condensor.

As a final act of desperation - don't forget the fuel side. I had one Minor that insisted on miss-firing on the way up the Pyrenees and Sierra Nevada mountains. It would only happen after prolonged full throttle up hills (which I thought was something on the electrics side overheating). That turned out to be fuel starvation but without giving the usual on/off/on jerking you normally get from lack of fuel in the carb.

Thanks you for your replies, I shall double up just to make sure.

Anytime you crimp connectors on wire(s), you should check the connection by holding the connector in one hand and pulling the wire w/the other hand. It should not come apart, if it comes apart it was not crimped properly.