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Hi

trying ti get my car running after a while of being off the road. Everything back in to my knowledge. I can not get a spark. Coil tests fine. HT leads are not new but were maybe 3 months old when car came off the road. I have to assume distributor is ok as it was when stopped using the car. 

Should i have 12v between the two small terminals of the coil when ignition is on. 

I dont really know enough to diagnose too well. 

There are two bolts through the lumenition box. One bolt is being used as an earth yermination point but its on fibre glass!  I have run a temporary earth from here direct to battery but no change. 

Does the distributor need to be earthed seperately?  The cable from the distributor and the luminition box has an earth. This however is only connected one end. Itdoes not reach the distributor. It has been cut off but has always been like this. 

Can a distributor be tested somehow?

Evan if leads and distributor are all in wrong position i should still get a spark?

If anyone can give me any pointers i would be very grateful

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have a look at this, it may be helpful. You can generate a spark from the Lumention box following the steps to test, particularly Fault Finding step 2. :)

Lumenition_PMA50_installation.pdf

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It's getting there......

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Thanks Tim. Will print this off and see what i can achieve. 

Its beginning to do my head now. 

Realised tonight that to remove the distributor you have to remove half the engine ancillaries. Its just a nightmare unless im doing something very wrong 

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Easiest is to disconnect the plug between the Lumenition module and the distributor. Switch on the ignition, then connect together, the blue and black wires from the Lumenition module. Connecting and disconnecting should result in a spark from the coil. If not, the fault lies on the distributor side, either a bad/broken connection or a bad optical sensor.

 

Of course, you start with the easiest things first.......ensure you have good connection between the Lumenition module and the distributor.

Edited by ekwan

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19 hours ago, PhilW said:

 

Does the distributor need to be earthed seperately?  The cable from the distributor and the luminition box has an earth. This however is only connected one end. Itdoes not reach the distributor. It has been cut off but has always been like this. 

.

As far I as I can remember it does need to be earthed. There should be 3 wires running through the Molex plug from the module to the dist, which are power for the sensor, ground and signal output. I dont think the sensor is grounded in the dist any other way.

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Lumenition module will require an earth connection. No so for the distributor using either Lucas or Lumenition AFAIK.

Edited by ekwan

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Im sorry. I have made an error. I have got a little confused...........and frustrated!

The control box is a Lucas AB14 Electronic ignition amplifier.  I therefore assume the earth as per the note above is not required?  I have been told today that with the ignition on I should have around 9V across the two terminals on the coil and 12V if turning the engine over.  THis I need to check.

Also told that taking the HT lead off the distributor central point and holding it by the block, in a similar way you might hold a spark plug when looking for a spark I should get a spark when turning the engine over.  This would confirm the coil.  I then need to look at distributor itself.  Do we all agree?

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As to your final point: If you did that and didn't get a spark, it could be the coil, amplifier switching unit, HT cable or pick-up in the distributor.

On the other hand, if you got a spark, then it would be distributor cap or rotor arm......logically speaking.

 

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There is a good diagnostic process in the service notes for the Lucas system.

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Thanks Andy. Ill check that

Thanks Ekwan. New dis cap and rotor arm so if no spark then likely distributor.  Just out of interest any idea for the best place for rebuild. I guess it nothing complex as its too old so probably a local place may be able to help rather than sending off to SJ’s i suppose

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3 hours ago, PhilW said:

Thanks Andy. Ill check that

Thanks Ekwan. New dis cap and rotor arm so if no spark then likely distributor.  Just out of interest any idea for the best place for rebuild. I guess it nothing complex as its too old so probably a local place may be able to help rather than sending off to SJ’s i suppose

Phil,

I'm not clear as to how a distributor could need replacement in this instance, the things really are quite rudimentary and don't do much other than provide rotating circuit paths to the plugs. Straight spark loss seems likely to arise from something like a failed connection or electronic component. The distributor has internal electronics in the form of a trigger ( substitute for points when electronically operated ) so try to rule that out. My experience with Lumenition's optical trigger unit was that it was utterly reliable. Don't know a thing about Lucas for this application.

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Just had a thought...

When you put the distributor back, did you make sure the dog was fully enagaged? Its possible to fit it and tighten the clamp when its not quite home. If this is the case, the rotor arm wont turn so you'd never get a spark. To test, remove the dizzy cap and turn the engine over making sure that the rotor arm is turning. :)


It's getting there......

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Those Lucas ignition amplifiers were a common failure on the V12 jags, even looks like the same part.

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33 minutes ago, Steve V8 said:

Those Lucas ignition amplifiers were a common failure on the V12 jags, even looks like the same part.

Indeed I believe there are more Lucas failures than Lumenition failures. But post when you have a definitive diagnosis and I am sure we'll be able to assist you on a cure.

No point speculating at the present moment as speculation doesn't get us anywhere, other than a possible betting win on a royal baby. 

Edited by ekwan

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33 minutes ago, ekwan said:

No point speculating at the present moment as speculation doesn't get us anywhere,

We can't all be scientific geniuses like you Eric.

Having had 2 Lucas AB14 ignition amplifiers fail on two different vehicles, both exhibiting the same symptoms (no spark), I'd say that puts me in good stead to offer my input, and is more helpful than anything you've come up with so far..

And I have checked, yes this is exactly the same problematic part as those used on the Jags.

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2 minutes ago, Steve V8 said:

We can't all be scientific geniuses like you Eric.

Having had 2 Lucas AB14 ignition amplifiers fail on two different vehicles, both exhibiting the same symptoms (no spark), I'd say that puts me in good stead to offer my input, and is more helpful than anything you've come up with so far..

And I have checked, yes this is exactly the same problematic part as those used on the Jags.

Yes. I've had a couple go as well, but I've also had my fair share of other wiring issues as well. Rotor arms are also an issue, but any electrical item is fair game. 

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Now who's speculating... :P

As these units are renowned for failure for no reason whatsoever and are unserviceable, so it makes good sense to look there first.

I don't believe there's a test for these amplifiers without specialist equipment, @PhilW if you have, or know of someone with a known to be working unit just plug it in to see if it solves the problem to rule it out.

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2 hours ago, Steve V8 said:

Now who's speculating... :P

As these units are renowned for failure for no reason whatsoever and are unserviceable, so it makes good sense to look there first.

I don't believe there's a test for these amplifiers without specialist equipment, @PhilW if you have, or know of someone with a known to be working unit just plug it in to see if it solves the problem to rule it out.

Speculating on which on my cars will that kaput first. 

When it will break down doing 70mph on the off side lane is also worth a flutter. 

Edited by ekwan

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Hi all

I have been through the tests in the service notes.  Seems like very possibly a new amplifier.  

Does anyone in east Anglia have a spare one I could come and borrow please? I have posted photos of the results.  Any further suggestions anyone?

Thanks

IMG_9439.JPG

IMG_9440.JPG

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Thanks Gis. Problem there is with uk bank holidaynso would get one Wednesday at the earliest

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Phil, can you clarify your results for test 2? 

Step 1 says your battery voltage should be 11.5v or higher (ignition on). You haven't written it down so I'll assume its OK.

Step 2 measure the voltage at coil, should be no more than 1 volt lower than step 1, therefore it should read no less than 10.5 Volts. You have written 0.6, if this is the drop the voltage you read was 10.9V? if you were only reading 0.6V then the fault is within the wiring from the battery through the ignition switch to the coil.

Step 3 should read the same as step 2 unless the wiring from the coil to the AB14 module and back to the coil is faulty.

Step 4 you have measured 8.4mV? therefore thats within the 1V max limit.

So as long as you quoted the voltage drop in step 2 and 3, I agree that the amplifier is probably the culprit. :)


It's getting there......

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Tar. Your right. Where have i got 0.6 from. Re checked and results re written. 

Looks like i have found an amplifier that i can go and pick up later today to borrow just for testing. Fingers crossed problem will be solved

455CA2B6-CD04-4F1F-838C-B2F22F204FE5.jpeg

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You should be able to repair the AB14 module for a relatively low cost.

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