Morris Minor Owners Club

Hi all, I've finally got my minor back together after engine rebuild etc but have a problem now with the ignition system! It's still positive earth, to begin with I didn't have a spark at plugs coil or points so I took points out cleaned and reset. Still no spark so I set about checking 12v was reaching coil etc then tried ignition again, this time the distributor started smoking. After turning it of and removing the cap the low tension wire inside the distributor was burnt out! (See picture) I found another low tension wire in my spares and after going over the system again and finding no obvious issues I tried again with the same result.....any ideas what is causing this?

Have you got the insulating plastic top hat washers fitted in the correct order. The top hat washers are fitted top and bottom of the moving contact spring. I suspect a direct short to earth.

Hi Phil I’ve got.... plastic top hat at bottom followed by points spring then condenser wire and low tension lead then another plastic top hat on top and nut? Picture added

You have got the wiring wrong on the coil or less likely a faulty coil.
If the coil is in circuit it will limit the current at the points.
I suspect you are getting the 12V direct to the points bypassing the coil.
12V ignition goes to the negative/SW coil terminal, the positive/CB goes to the points.
Regards John.

Well you have got the top hat seals and wires in the right order/place.
Just make sure that the spring has not cut through the top hat and is now earthing.

The problem is direct earthing after the feed into the distributer - all you can do is replace the wires again and check the wires carefully to ensure they are not fouling on moving parts.

As above make sure that the coil is connected up correctly.

Thanks chaps, I'll strip it down again and check. So on positive earth the two white/black wires are to negative terminal on coil and positive is to low tension connector is that correct?

Just taken a look at the coil connections, please see pictures...I have the white/black and white wires to positive and green wire to negative a black/white wire from loom is connected to distributor? 2nd picture?

The coil is wired incorrectly
The White goes to the negative coil terminal.
The White/Black goes to the positive terminal.
The Green/Yellow shouldn’t be on the coil it should be on the oil pressure switch or the blocked filter switch, if the latter just leave disconnected.
Regards John

Thanks John I appreciate the help, I’ll change around tomorrow and let you know how I get on

Regarding the Green/Yellow wire, for a short period of time they fitted a blocked filter switch and warning light along with the oil pressure switch and warning light both using Green/Yellow wires. The blocked filter switch and light was later discarded but the wiring loom never got up dated so the wire is still present but has no use and is left connected to nothing. So if your oil pressure light doesn’t work the wires need swapping over. The G/Y wire didn’t cause your problem, the White and White/Black wire connected to the same terminal did cause your problem, supplying 12V direct to the points, luckily the weakest link in the distributor burnt saving the wiring loom as the White wire isn’t protected by a fuse.
Fingers crossed for tomorrow.
Regards John

StillGotMy1stCar wrote: ↑Wed Jul 10, 2019 11:27 pm Regarding the Green/Yellow wire, for a short period of time they fitted a blocked filter switch and warning light along with the oil pressure switch and warning light both using Green/Yellow wires. The blocked filter switch and light was later discarded but the wiring loom never got up dated so the wire is still present but has no use and is left connected to nothing.

You would think that they would have at least snipped off the redundant wire instead of leaving it hanging around to confuse future owners. This isn't the first time a blocked filter wire has been wrongly connected to the coil!

There is a greater underlying problem here. The circuit through the coil, pigtail and points is grounded (whenever the points are closed). Should not exceed about 4A, which should not melt the pigtail lead. The converse actually - the coil normally will get hot if the ignition is left switched on, without the engine running, and with the points closed.

The "low tension wire" in the dizzy is to the condenser. When you "replaced" the wire, did you swap the complete condenser (the round metal thing with the bracket to attach it to the baseplate) or did you connect a new wire to the existing condenser? If the latter, then it could be a faulty condenser in addition to the incorrect wiring. If you replaced the condenser then it's unlikely that two will be short circuit.

Coil wires corrected and it fired up nicely. Thanks all.