A Non New Year run with no spark

[Andy Bennett]

Hi everyone
In wishing you a Happy New Year, mine has not started well.
 
I have 1933 Box running coil ignition, standard dynamo, with Accuspark distributor.
 
Having not run the car for some time I started her up yesterday with no problems.
This morning on getting ready for our New year day run, she turned over and then after a revolution almost stopped with a resistance and then turned over again, but did not start. This repeated. There was no backfire or clear misfire but it felt like she was trying to fire at the wrong point causing the ‘stopping’ of the engine.
 
Just to state that there was plenty of fuel.
I started working through the ignition. There was apparently no spark when holding lead off the plug or against decent earth.
Rotor was turning.
I changed the coil for a new one (not tested). This time the engine span freely with no ‘stopping’ but would still not start and no spark seen when removing a lead and putting lead close to plug. 

It then briefly half ran as if on only 1 cylinder and really struggling. 
 
I then replaced it with the original coil I took off about 8 years ago and which was working fine when last used. This time the tightening/stopping came back but still no spark.
 
I then took the Accuspark distributor off and replaced with the Bosch (again was fine when removed). Would not start, but when I played around with a lead on a head stud I saw a very faint spark. I could almost convince myself that I did not see it, but it was definitely there. But it was not enough to show any signs of starting. Tried new condenser, no change. Points opening fine.
 
There was 6V on the coil terminal with ignition on.
 
So I decided to stop there and think a while.
I realised that there was no discharge showing on the ammeter with ignition switch on. At rest ammeter was at 0A. When I put the lights on discharge was about 5A.
Looking at old posts on here it suggest that discharge with ignition on but not running should be around 6A. I should know, but I couldn’t say what it usually is, but not 0.
 
So is this my problem, whilst I have 6V from ignition at the coil, I have no current to drive it?
If so, where has it ‘gone’? The ignition switch clearly works to the extent that it supplies 6V to coil and switches the lights on and off.
 
Appreciate thoughts on whether or not I am on the right lines/looking at the right place (ignition switch, cut out?) and if so what the problem might be in the apparent resistance or breakdown and how I might hunt it down.  
 
Appreciate thoughts from a very frustrated (non) driver for what would have been a lovely New Year run.

Andy

[John Cornforth]

Hi Andy

A standard coil will draw about 4 Amps with the contact breakers closed.  When the engine is running it draws this about 50% of the time, so the average current is nearer 2 Amps.  You should measure about 6 volts between the "Switch" side of the coil and ground, whether the coil is drawing current or not.  I suggest that with a points type distributor fitted and the cap removed, you turn the engine over slowly on the crank until you see the points are closed.  Then turn on the ignition and measure the voltage to ground at the coil "Switch" terminal and the Coil "CB" terminal.  These should be about 6 volts and a small fraction of a volt respectively.

I suspect from your description that you have a high resistance / bad connection somewhere in the LT side of the ignition system. The ignition switch is one possible culprit.

[Andy Bennett]

Thanks John.
I have 6.07V at the ignition terminal with ignition on, points open or closed and 0V on other terminal (which is strapped to earth/body).

Also just to note I am positive earth.

Andy

[Reckless Rat]

Is the distributor properly earthed?

[Mark Dymond]

A temporary wire from the battery to the coil will eliminate problems from bad connections. A jumper cable can be used if you have one, connect from the battery -ve to the coil, ignition side and see if she will start.

good luck

[Andy Bennett]

A temporary wire from the battery to the coil will eliminate problems from bad connections. A jumper cable can be used if you have one, connect from the battery -ve to the coil, ignition side and see if she will start.

good luck

thsnks Reckless, yes have checked distributor earth.
Mark: you read my mind. That realisation just went through my mind as I was munching on a mince pie. was just going to post a 'I'm not going to do any harm to anything am I' and saw your post.
Off to make up a lead.
Andy

---

hmm
Made a lead and it made no difference, no spark whatsoever.
Checked with lead and 6V measured with lead.
Rechecked timing and is broadly TDC so should have kicked into life if not run well.

Am running out of ideas. 

Andy

["Slack Alice" Simon]

Dissy drive gear lost its teeth or slipping on shaft?

[Ruairidh Dunford]

Andy,

When using the wire from battery to coil make sure the coil is isolated by making sure the ignition is off or, better, the feed completely disconnected.

Do you have a new spark plug to try?

Are you using different spark plug leads when swapping between the distributors, if not, consider making up a new king lead.

Have you tried to tow start the car?

[Andy Bennett]

Thanks everyone, as ever some great thoughts and advice.

Well, short version is that I am up and running. Long answer is that I am not quite sure why and I hate those situations as they can happen again tomorrow.

Ruairidh: I did take the ignition lead off so it was completely disconnected. I was also using my old set of leads with the Bosch dissy, so a completely different set. I do have some new plugs but didn't change them.

So what did I do since my last post? Well, I added an additional earth lead from the dissy just to be sure, but this made no difference, not a hint of a start. Then I rechecked the Bosch dissy and decided that the points gap was a little small (about 8 thou) so reset it to 12 thou. I then redid rough timing by just putting thumb over 1 plug hole and setting by eye the points opening at TDC.

Then trying again it spluttered into life. I played with the timing a little more and it ran sweetly.

I then disconnected the ignition bypass lead and tried again and it started first time (it was of course warmer at this point).
Ran for a few minutes and all seems OK.

So from the first set up where nothing ran, the only thing different is the dissy (now Bosch, was Accuspark) and an extra dissy earth lead. Not forgetting that many leads have since been connected and disconnected, jogged etc.
But when I changed the dissy earlier today it made no immediate difference, so I have no evidence to determine it must have been the Accuspark dissy at fault.

So I am left pleased that it is running but frustrated, wondering if it will run in the morning.

It is of course possible that the Accuspark unit has failed and that the Bosch dissy was not set up well enough at the start, but I would not have thought that an 8 thou gap would have rendered it useless and I reset the timing 3 or 4 times with no luck, so don't see that I suddenly made an amazing change to my rough timing setting.

I think I will go through all leads etc to clean and remake joints to give me some peace of mind in case I have a simple bad joint that I jogged into being OK for the moment.

I will contact Accuspark to see what they suggest if there is a simple test I can do (wishful thinking I fear) as i am not inclined to refit it with lead changes etc.

Thanks again for everyone's help.
Andy