Lucas electronic ignition - no sparks

[Gridgway]

All questions are good questions!  I'm actually using a spare battery as the one in the car was completely dead.  It charges and has 13+ volts.  But I could try a different one.  the +v are definitely getting to the coil and the AB14 box is earthed.  I've done the earths (including removing the cut-off switch which is between the -ve side of the battery and earth(.

With the dizzie out and being turned using my drill (the right way, I've triple checked) I earthed it using a big fat jump lead.

I will recheck that the body of the HEI module has a sound earth.  The heat conducting paste that came with the new module looked very much like silicon grease to me which I think is an electrical insulator and the bolts that hold the HEI module into the AB14 casing provide the earth.  I'm sure they will be doing that, but it's worth double checking.  Not come up with anything else to check yet.

[Gridgway]

I question for jbcollier, you mentioned the figure of 2v AC from the reluctor when cranking.  I only managed to get 0.1v AC from my new multi-meter (turning the dizzy with my battery electric drill which I think is faster than cranking speed).  Reading on the internet about one specific version of the 4 pin module here, it says that the module will provide a bias voltage of an amount just below the turn off voltage, ie just under 1.43v.  But the turn on voltage is 1.64v.

So the 0.1vac measured on my meter, assuming that is the RMS voltage will give a peak voltage of root 2 times that = 0.14v.  So, assuming the bias voltage is 1.4v, the resulting signal voltage will vary between about 1.54v and 1.26v, so the coil will never get turned on, no spark will result.

I've probably just written and load of old nonsense from 45 years ago mis-remembered A level physics!

[Gridgway]

I think I'm even boring myself now, but here goes.

This evening I made some diagnostic progress.  I re-did the "get a spark out of a coil" test on the bench with a spare 12v battery, spare coil, plug lead and spark plug and some wires.  Easy that got a spark,  So I repeated the same test in the car with the coil in the car and battery.  Lo and behold a spark.  The coil works.

Then just a quick check with the same king lead wiring (well it was better earthing that did the trick), plus the ignition box and the dizzy driven from my drill (circa 500 rpm).  Nothing.

I also used a pin to properly check the continuity of the squished wires from the dizzy, all good.

Then from my readings linked above and this link I got the old ign module and did the voltage measurement which gave 1v.  That's none of the readings in the link (being 1.25v, 0.77v or 0v).  But I took it as a sign that the module may have life.

Then buoyed by my success I thought I would apply a voltage to the input, using an LED as my pretend coil.  This is noting from above that 1.64v or similar might be the coil turn on voltage.  I used a 1.5v battery.  Imagine my surprise when the module turned on the LED pretend coil.  I said oh my!  So the 1.5v might be above the switch-on voltage, but the 1,5v plus the 1v bias voltage definitely is.  So I think the ignition module might be working.

In a fit of pique, I then connected up the dizzy in place of the 1.5v battery, turned it with my drill and nothing happened

The signs point to the reluctor gubbins in the dizzie.  As it happens, a friend is chucking out the same setup from his formula Atlantic race car (in favour of lumenition).  So I should be able to get his cast off reluctor gubbins and AB14 module.  We know his works, just not very well at high revs.

The temptation just to buy a Lumenition is quite big, but I want to get the Lucas setup working as a matter of challenge!

i'm certainly learning a lot!

[Gridgway]

That's the waveform for a reluctor I believe.  Definitely AC, but not a sin wave.  So my calcs about peak voltage up the way won't be quite right, but still good enough I reckon.  That's now my favourite for being faulty.  Hoepfully we'll see soon.

[jbcollier]

I'm very interested to hear the results.

What coil are you using?  HEI does NOT use a conventional coil.  Been a long time and I can't rememeber the difference but they all looked something like this:

Some websites that might be useful:

https://www.gmcmi.com/wp-content/uploads/2014/05/HEI-Testing.pdf

http://www.pontiacpower.org/HEI.pdf

https://garage.grumpysperformance.com/index.php?threads/trouble-shooting-rebuilding-hei-ignitions.2798/

[Gridgway]

#30 thanks for the references, I'll look them up.

There isn't a massive difference for the coil.  You need a low resistance primary winding to get the highest current to "charge" the coil as quickly as possible.  That then has the possibility to overheat easily.  The HEI system though does dwell control to use shorter bursts of higher current without overheating the coil (or itselft).  So a regular coil (for points) will have 3+ ohms maxing at 4 amps.  Also a ballast resistor is used to stop long periods of high currents with the ignition on and not running (for example).

The HEI system produces constant energy sparks across the rev range with the dwell control, but it needs a coil with a resistance of 1 ohm or less to do it.  That's the main difference.  Also the coil construction might be optimised to manage heat from the higher currents as well

 

[Gridgway]

One of the areas I'd not contemplated in my thoughts so far is the ignition advance.  As far as I can see, the Lucas dizzy is completely locked.  It doesn't have any vacuum advance and the base plate is locked with no movement as far as I can see.

That would mean that the HEI module must be doing rev related advance.  I can't find any reference to it though in all the reading I have done.  I guess if I ever get it running, I'll be able to check the advance at various revs with my timing gun.

I must admit that my thoughts are moving to change it out as I'm not sure of my next move to get it going!

[jbcollier]

The HEI module does not control advance.  It would have a mechanical advance underneath the plate.

[OldAndrewE]

It doesn't have any vacuum advance and the base plate is locked with no movement as far as I can see.

The base plate will be locked/solid because you don't have any vacuum advance.  The centrifugal advance moves the bit of the shaft with the points cams in relation to the gear that engages with the camshaft

[Gridgway]

Thanks Andrew, the only other distributor I have worked on did have vacuum advance, but I thought the movement of the baseplate was the mechanical advance.  It was a very long time ago indeed!  Just had a quick look and yes the shaft at the bottom moves in relation to the shaft at the top.  I'm definitely enjoying learning stuff.  Mind you, I think I should have known this from my youth!

[Gridgway]

A quick update, (trying to keep my ignition threads seperate), I have spoken to H&H and we have concluded that I'll send them all the bits and they will diagnose and repair accordingly.  They can also check the advance being correct for the engine/cam/carb combination.  Will obviously take a while, but should solve the problem.  I'll be interested to see what they find!

[Gridgway]

So an update from H&H.  The module in the dizzy is dead, £30 for a new one, simple as that.  I should have had the courage of my diagnostic convictions as that's what I concluded.  But at least I have the problem, got a solution and know that the AB14 and the coil  are ok.  The original HEI module plus the cheap ebay one I bought both work ok.

Just need a new fuel tank to put in and I'll be ready for engine start!

Graham

[Jonathan Kay]

Sounds like progress. Thanks for adding the answer.

Jonathan

[Gridgway]

When it's done, I'll do a summary of my diagnostic steps should anyone else have the Luca Rally or other HEI based ignition.

[Gridgway]

To conclude (famous last words) I tested the setup on the bench with an LED instead of a coil, see here for vid.

Today I put the ignition system back together in the car and tested that there were sparks which there were.  All very good indeed - happy ending.