Irritating Points Ignition Failiure - a bit stumped!

I will do.

Did you not read my post about checking it with a DVM?

And here's a crude, but effective test you can carry out. Remove the dist cap and rotor arm, leaving all HT leads connected. With ignition on and points closed, put the rotor arm on the end of your finger, and hold it so that the centre contact is touching, and align it with the contact that goes to no 1 plug lead, but not touching. Now flick the points open with your other hand, watching the gap between rotor arm and plug lead contact. Then move the rotor round to point at the next one, and so on. This will let you know what sparks are going where. Occasionally you may find that the spark ignites the fuel in the cylinder if you've been turning it over. Apart from giving you a brown trouser moment, this doesn't do any harm.

Steve

Yes, thanks. I'll have to do it this weekend - I'm away with work ATM.

It is always better to try and find an actual fault than to attempt to fix it purely by parts substitution. Unless you are absolutely certain the part you're substituting is good.

As I said, there is a lot of rubbish out there being sold new for classics spares - like the Lucas repro dizzies. They may be cheap - but if you examine one you'll see why.

Other thing is if you've been attempting starting the engine with no spark the plugs may well be fouled and not work properly even after you fix the fault.

REminds me of a job a good few years ago, a mini came in: it ran fine till you went round a right hand corner fast, then it would run rough and might even cut out and after a few minutes would go normally again, the fault was quite reproduceable, I decided it must be some sort of fuel starvation fault and rigged up a completely separate fuel pump and tank: same problem, stripped the carb, all was good. Eventually I decided it was not fuel as even squirting fuel straight in the inlet would not make it go, so I took a good few tools out with me as the fault could not occur till hard cornering. Discovering that when it stopped there was no spark I narrowed it down to the CoiL WHICH WAS NEW, replacing it with an old one I found in the boot fixed it. The mini coil was mounted sideways, when you cornered hard the oil insulation in the coil was running to one end and the spark was shorting internally.

Thats why I mentioned "coil". It might produce a good looking spark in fresh air but not have the "oomph" to make a good spark under compression. Easy enough to check. Dave

But it doesn't make a good looking spark at the plugs even in fresh air.

Late to the bunfight but two points:

Good luck!

I rode a motorcycle 10 miles home without a proper engine earth. I knew I'd lost the earth as every time I touched the clutch lever I was attached to the ignition earth path as it was earthing though the clutch cable.

critcher said....... change the plug leads, they do sometimes fail if they are carbon cored. It's not a lot of money to eliminate them from the equation.

It's also even easier to check them with a DVM. For free.

Here is another HT diagnostic aid. Take one HT lead with suitable ends already fitted. Cut it at some point, then push tacks or similar into the core either side of the cut. Find a short section of clear plastic tube which is a tight-ish fit on the HT lead and rejoin the HT lead, leaving a small gap between the tacks. You now have an HT spark indicator.

or just buy a cheap ht gauge from halfords, the gap is instantly adjustable and gives you a good guide as to the voltage, I like your idea too.

And I'm guessing if you could see the spark with a Colourtune plug the engine would be running. ;-)

Cheers, T i m

In article , Dave Plowman (News) scribeth thus

Well.. I had a bit of a misfire on the Audisaurus sometime ago and admittedly the leads were old and prolly poor, so new plugs and leads and misfire gone but I'd add that this did take sometime to develop that problem..

Anyway measured the resistance of the leads and they were slightly lower ohms than the new ones but the new ones worked the old ones misfired..

However I very much doubt that this was the problem with this sudden stoppage.

And as to that .. any further forward as yet?..

Obviously as with caps an rotor arms, you give them a good clean first and a visual inspection. Looking for cracks or signs of tracking.

The resistance isn't an absolute figure - what you're looking is for one which is very different - like say instead of 5000 ohms 50,000 plus.

In article , Dave Plowman (News) scribeth thus

As best I remember there was nothing in it to speak off....

I've checked the leads but may have cocked up - I also didn't have a tape measure for length. Measured on the 2000K Ohm scale

King lead 17 (Same length as 6)

Not sure what to make of that.

Cleaned the pins inside the distributor and I can now see a blue spark at the plug in air - not the strongest but it can be seen and heard. Still no start.

The spark between rotor and distributor is pretty feeble.

Can't get a new cap off the shelf today.