no spark

[jeff jackson]

Hi all,
This has me stumped.
I posted a while back about the Aldon ignitor module, I had broken down on Boxing day.
I convinced myself that it was the module that had packed in.
I have decided to build my own ignition module, but whilst that was going on go back to points and condenser.
I have also been suffering from a chest infection, so not able to get out into the garage until today.
I have put the points back in, static timed it and fired the car up. No spark, or no light from the timing light.
I have checked the coil and all is good. I have a good 12V at the coil and with advice from a previous thread, checked the current in line when points are closed and points are open. I get 4A when the points are closed and 0A when closed.
With the ignition on, and points closed, I can get a spark across the points gap if I manually open them.
I have a reasonably new distributor cap and new ignition leads.
So any I deas what coud be the problem?
Could it be the rotor arm? never had one of those be a problem before, but out of ideas now.
Any help gratefully received.
Kind regards
Jeff 72+2

[David1953]

I have had several bad rotor arms. Brand new and last about 50 miles!

I am now using a very old one that gives no problem.
(this is actually on an Esprit, but I think it applies here)

[jeff jackson]

Hi David,
Thanks for your reply. What were the symptoms of your rotor arm failing?

How can a rotor arm fail? I have just had a look at mine and it does not seem to be damaged at all.
Can they cause a short?
Somewhere ddep in the depths of the garage I have an old one. Maybe try that tomorrow.
Regards
Jeff

[alanr]

Slightly confused by you saying that you 'fired the car up'.
I assume that you mean that you attempted to start the car and it wouldn't start..aka would not 'fire up'?
You say that you have a spark at the points but do you have a spark at the spark plugs?...Have you tried removing a spark plug ,earthing the plug with the HT lead connected and turning the engine over on the starter. Is there no spark across the spark plug electrode?
If so, some other suggestions are:-
Is the carbon brush in the distributor cap still in place? it is on a spring and if worn can stick in the dis cap..Also check the distributor cap itself for arcing .
Also as others suggested a suspected faulty rotor arm is a possibility especially if the metal segment is of the rivetted variety.

Alan.

[jeff jackson]

Hi Alan,
Thanls for your reply.
Sorry meant to say Turned the engine over on the starter motor, with my timing light connected. No light, meaning no sparks. No attempt by the car to sputter into life
Before I took it all to bits I tied a spark tester, and that had no spark. Also connected the timing light, hence my assumption of the Aldon unit.
.
As I mentioned before it was running and then died on a busy dual carriageway.
The distibutor cap is good, the brush is intact, springs up and down and is fairly new.

The rotor arm is the riveted type so could be the culprit.

[David1953]

Jeff
The symptom was lack of spark. Lots of misfiring on the road, stopped to look and would not restart.
Replacement rotor arm fixed it.
To be honest I do not know how it failed, I assume it was breakdown via the rivet, but it still looked as new.

[alanr]

Jeff,
Whilst a faulty rotor arm is still a good bet.
Other thoughts:-
You say you have spark at the points LT. Have you thought about a faulty coil, HT side?
Check for spark out of the coil, HT spark. Either disconnect the centre HT lead from the distributor and hold 1/8 inch away from earth whilst turning the starter over or it may be easier to just flick the closed points whilst holding the HT lead away from earth. An alternatively method is if you have a spare HT lead, use that out of the coil and test.

One more thought, points can sometimes fool you. If the points are dirty on the contacts you may still get a spark when flicking with a screwdriver but when the engine is turned over the contact between them breaks down.

I am not saying this is the case here but I wouldn't lay too much faith in the fact that the timing light doesn't work, all that means is you don't have spark at No1 spark plug plus I have seen faulty Snap-On timing lights fool people more than once.

Alan.

[jeff jackson]

Hi Alan,
Thanks again for the reply.
I did test the Coil with a multimeter, compared that with another coil and the results were the same, although I take your point that under load it could break down.
I will try all you suggest tomorrow.
Thanks again
Jeff

[billwill]

Rotor arms can fail by burning a track through the top from the brass spark plate to the stem of the distributor. The result is impossible or near impossible to see and does not show up on a multimeter (as it only conducts at high voltage).

The only effective diagnosis that I have found is swapping it for a good one.

[RichardHawkins]

Jeff,

There is a small company (probably just one man) called distributor doctor. I think he is in the south west of the country. I have heard good reports, and apparently he has stock of good components.

Richard Hawkins

[jeff jackson]

Hi Richard,
Thanks for the tip, yes I have heard of the distributor Doctor.
I will give him a call tomorrow, as He does not operate an online service, but prefers to talk to you and get you the right part. Fair enough.
Regards
Jeff

[richardcox_lotus]

I?ve been using his rotor arm for the last few years - no problems. Note it?s not a rev limited one...

[denicholls2]

How can a rotor arm fail? I have just had a look at mine and it does not seem to be damaged at all.

The ignition system is very high-voltage, pretty much like creating a lightning bolt between the coil and the cylinder head. Lightning has one goal: Find the shortest path to ground and follow it. By design, that path is through the spark plug's electrode(s) and insulated from shorter paths by the plug wires and design of the ignition system. But as soon as a shorter path presents itself, that path will (indeed must) be taken. Lightning falls easily to temptation.

Common short-cuts are:

Carbon traces caused by earlier misfires in the circle between the four distributor cap contacts
Carbon traces caused by vertical cracks in the distributor cap collecting conductive dirt
Carbon traces at the connection points of the plug wires between them and the coil wire.
Short paths to grounds introduced by the cylinder head or block through cracks in the plug wires contacting or in close enough proximity to them to be easier to follow than the spark plug gap.
...etc.

[jeff jackson]

Hi all,
A recent post suggested that any "cry for help" should result in a "what happened" reply.
I reached out to the community, because I was stumped why I had no spark and also why the Elan broke down on Boxing day.
I have a resolution...and it was the ROTOR ARM!!!!!

I have never had that fault before, coils, points, condenser, dizzy cap all have failed in the past, but were easily recognisable as the root of the problem.
So you learn something every day.

Thank you to all who replied and hope this helps someone in the future who searches for "no spark" on the forum.
Thanks again,
Jeff with a running 72+2!

[alanr]

Good one. Pleased you got it sorted!
Those rivetted rotor arms are total rubbish and always need to be avoided!

Alan.