HELP! Whats wrong with my 123 dizzy?

[RogerD]

Hi All,
I bought a 123 Tune distributor for my Mk I Vitesse a while ago, and I did manage to start up the engine and had it running decently for a while. Then I had some problems with flooding carbs due to fuel pressure being too high, so I have never driven it on the road with the 123 Tune. Last time I tried to start the engine it behaved really strange, barely running. I suspected something fundamentally wrong with the ignition, like if I had put the plug leads in wrong order, or mixed them up in some way.
I have an “ignition tester” which basically is a light bulb connected between the spark plug and plug lead. It lights up when the spark comes (I will try to include a picture if I can…). The weird thing is that when I use the “ignition tester” on number one cylinder I get a spark not only when it is supposed to be there, but also about 60 crank shaft degrees later, and I get (I think) about 3-4 sparks in 720 crank shaft degrees, instead of one, as it should be.
I’m not good with electrical stuff, I’m more into mechanical things. I hope there are some electrical wizards here that can explain this, and please tell me that I’m doing something wrong, and that there is nothing wrong with my VERY expensive distributor! 😲

[Nick Jones]

Don't know about your 123 question.......  However, if your engine has been flooding then it is probably worth trying a new set of plugs.  My experience in recent years is that some spark plugs, especially new or nearly new NGK, cannot handle being flooded and don't work properly afterwards.

Nick

[RogerD]

Thanks for your reply Nick,
This might give some more clues: I removed all spark plugs and plug leads when I did the first test with the ”ignition tester” (in order to make it easier to turn the engine by hand). Today I did a new test, but this time I had all the plug leads in place and the spark plugs connected to earth so that I got a spark on all 6 cylinders when I turned the engine. This time I got a slightly different result. I still get several sparks on cylinder no one in 720 degrees, but now most of them are hardly visible (very weak) except the “real spark” at 13 degrees BTDC which is quite strong. I suspect that the current which should go to the other cylinders somehow “leaked” and got to cylinder no 1 but with reduced magnitude. I don’t know it this make any sense at all, as I said, I’m definitely not an electrician…
I guess I just have to start up again, using my new HUCO low pressure fuel pump that arrived yesterday 😀 and see what happens…
Cheers,
Roger.

[piman]

Hello Roger,

you can get induced voltage in spark plug leads, especially if you tidy them up by cable tying them together for neatness.

Alec

[Spider]

Any cracks in the distributor cap will allow tracking between leads. Not usually visible with the naked eye but try rubbing graphite (pencil core) over the distributor cap and the edges of the crack will pick up the graphite. Don't always trust a new part either, they are untested, so an unknown quantity, besides just because you have not dropped it someone that has handled it between manufacture and delivery may have.