123 Tune.....I am not so sure anymore 1962 3.8

[andrewh]

So firstly, I do hope you and your families are keeping safe in this most dreadful of times. Like all of you it feels almost surreal and in an attempt to direct my over active imagination away from current affairs I took to the workshop. I feel sure I am not alone in that!

Since I decided to replace my fully rebuilt Lucas distributor, leads and coil with a 123 to be honest she has never run perfectly since. There has always been intermittent misfires for apparently no reason. At the time of buying into the 123 Dream I also decided to park my original bow tie caps and plug leads and acorn screw in distributor. Not sure why to be honest? A boredom purchase? A desire to improve what we all know is an almost perfect car to start with
I purchased a set of Rob Beere Moroso resistor leads and separator and its reasonable to say I have had one or two ok on all 6 experiences, but most of the time I have a misfire. I have checked earths and plugs and pretty much the obvious things but I am beginning to think that replacing analogue with digital is not the way to go on an XK engine. Probably like most of us, I put a lot of work into my cars and when it doesn't run right it causes me much stress, particularly as I am pretty sure this is down to replacement tuning accessories . I still run my original Dynamo, again fully rebuilt, but it does register quite high on the charge but I dont think its over charging. The 123 does seem to be pretty sensitive to lots of outside influences. Can anyone shed any light on similar experiences and perhaps stop me from switching back to standard? I suppose I should say that I was attracted to the idea of being able to fine tune my ignition curve to my engine specification, but increasingly I just want my lovely 3.8 back.

[Heuer]

Are you using resistor plugs? I had a misfire with the EDIS/Megajolt and after much testing found it was down to using non resistor plugs even though I had Moroso HT leads. Try a set of BPR5ES plugs - £1.93 each at Amazon.

The non-resistor plugs causes electrical noise which interferes with electronics including mobile phones and SatNav's.

[Philk]

I looked into putting a 123 into my 3.8 when I was having my mechanical restoration done a couple of years ago. I eventually decided on going the "halfway house" of putting a Pertronix (LU-166AP12) into my original distributor simply to "up" the spark and to remove any unreliability from points and rotor. It has worked perfectly since with no issues (with silicon leads). At the same time, I put a +ve earth Dynator into the system. Again, it has worked flawlessly.

[andrewh]

Are you using resistor plugs? I had a misfire with the EDIS/Megajolt and after much testing found it was down to using non resistor plugs even though I had Moroso HT leads. Try a set of BPR5ES plugs - £1.93 each at Amazon.

The non-resistor plugs causes electrical noise which interferes with electronics including mobile phones and SatNav's.

Hi David, no its on non resistor set of plugs which worked fine with the original Lucas distributor. I have ordered some BPR5ES to try those. Never too happy with trial and error as I like to understand the reason for the problem, but of course with black boxes it could be anything ! thanks David

[mgcjag]

Hi Andrew are you sure you misfires are not down to a weak mixture...or is it very intermitant..can you produce the mis fire consistantly....i had an intermitant misfire took me a year to find...turned out to be a wire slightly loose in a spade terminal on the coil...only found it when i pulled on the wire and it came out of the spade....so check all you connections...better still run some temporary wires to bypass the ignition switch etc.... Steve

[andrewh]

Well I am not sure of course but will check again Like all good upgrades it was running great before! There is no doubt that one downside of an electronic ignition is they seem far more sensitive to resistances etc. I did previously identify a faulty connection as a problem. Thanks Steve.

[PeterCrespin]

I don't count myself an electronics expert by any means, but I have fairly often used electronic ignition since the Boyer-Bransden modules came out for British twins in the late 1960s. It is my experience, FWIW, that apart from iffy voltage supply and/or heavy RF 'noise' affecting things, it is in the nature of electronic ignition to work until it stops. I.e. the switching of coil supply either works correctly or not at all. 'Misfires' tend to involve separate componentry downstream' of the electronics. I never used carbon leads or resistor plugs but can totally believe the lack of same may cause issues with the more sophisticated systems available today.

Funnily enough, I had to bump-start my modern Triumph a couple of times last week (my own fault) and it took me back to the occasions as a student when I not only had to sometimes bump start bikes but had to do so fast enough to make the alternator generate a stable supply. Points would give a spark at the correct time whenever there was even 6V on offer, but electronics didn't just need juice for the primary windings but also a minimum of about 9-10V to work the circuitry correctly and time the ignition. The modern bike needs a decent supply to work the EFI as well, so bump-starting was not on my 'wish list' that day.

[politeperson]

I have found the 123-Tune to be completely reliable.

I first fitted one to an engine 3 years ago, it took minutes to set up at ran perfectly until I changed change for FI.

It has been fitted to 2 more XK engines to fault find, they just strike up and run perfectly on it.

One issue I had was that one of the rebuilt engines had its distributor drive fitted 180 degrees out. Once that was bottomed out there were no issues.

The infamouse Jaguar cylinder numbering system (1-6 backwards) causes some head scratching, as the 123 instructions which want you to time it on "No.1".

On an XK engine, number one is at the back of the engine. The distributor arm needs to be pointing towards the front cylinder (No.6!).

The front cam lobes need to be pointing outwards (look through the oil filler) with the crank on 10 degrees top dead center (only visible from underneath the engine as that is where the pointer is!.

Resistor plugs are important.

[rfs1957]

If anyone wants a free Aldon Igniter, send me a PM.

Sorry, Positive Earth only - I've moved to Negative and it's now surplus to requirements.

It's 15 years old and still works perfectly, but I have had the distributor Doctored back to "points" by Dr Distributor (painful at £300-odd including a new shaft, but absolutely perfect) as that will from now on be my Plan B ignition alongside the Megajolt.

I had bought a -ve Earth Aldon, but as the instructions are so crap, one of the critical screws supplied is still too long, and the type of grommet furnished is still completely wrong for the DMBZ (both problems I first complained about 15 years ago) I ended up returning it in disgust, tired of buying stuff from suppliers who DGAF about the customer experience.

But the product does work and it's been 100% reliable for me.

[Heuer]

Hi David, no its on non resistor set of plugs which worked fine with the original Lucas distributor. I have ordered some BPR5ES to try those. Never too happy with trial and error as I like to understand the reason for the problem, but of course with black boxes it could be anything ! thanks David

This is the difference between standard and resistor plugs:



"At the moment the spark jumps the gap it causes a high frequency burst of energy, this is known as RFI (radio frequency interference). This is why resistor spark plugs were introduced in the mid 1960's. Placing a resistor within the spark plug suppresses the RFI. Without resistor plugs in your car you can experience static on your radio as well as interference with other sensitive electronic equipment. Some later model vehicles as well as newer Powersport engines must use resistor plugs for a proper "talkback" to the electronic ignition. As a rule, performance is in no way impaired by resistor spark plugs."

[rswaffie]

I can only speak from recent experience with fitting the basic version of the 123 to my +ve earth 3.8, but it is working well. No misfires etc. However, I found that everything within the ignition system (including the static timing) has to be correct before you start. I used the bpr5es plugs and the recommended shielded ht leads and followed the 123 instructions to the letter. However, I had different issues caused by a lack of engine earth that kept blowing the electronic module in the 123, so put the newly rebuilt Lucas dizzy back in and got it running on that. When I traced the earth lead fault (which also screwed my dynalite ) I took it to the rolling road who put the new 123 back in and tuned it with that - they much prefer the 123’s to the standard dizzy.
What mapping for the 123 are you using? If the misfire is at a particular rpm point, could it be worth trying a different setting?

[andrewh]

thanks Guys. There isn't an issue with the fitment of the Dizzy. I had a perfectly good run to Goodwood and back in September. I have fitted three of these now and to be honest the other two worked fine. I am beginning to think the issue is going to turn out to be the lack of resistor plugs, thank you David for the above. The problem with me is having a few different cars I get sidetracked and then forget where I got to with the problem ! there is a lesson there and I am going to have to start writing things down in a note book I leave in the car I think. Anyway, I recall now, that I did have a misfire previously on this installation and discovered that one of my spade terminals was not a perfect connection. I need to revisit all my connections and fit my soon to arrive resistor plugs. What did it for me was that I moved the E type 2 weeks ago and it was running superbly on 6 and desperate for a run. Yesterday I fired it up and it was immediately fluffy. I ran a temperature sensor over all the plugs and they are all operating but perhaps not all the same. I suppose its just the fact it intermittent thats annoying me.

[abowie]

I'm a Luddite. Put the points back in.

[andrewh]

Well I have received my new plugs, but in the process of changing them out, they all smelt a little of stale fuel. Something I grew up with as my father had sheds full of old vehicles that had not run for years. They say smell is one of the strongest senses, and it always takes me back to sitting in his wartime Jeep completely covered but for a mouse hole for me to crawl into the drivers seat. Stale fuel. anyway, sorry I digress. I reckon this is the problem we all face every springtime that the fuel has gone off over the winter. The car starts and runs like a load of old nails, the fuel partially burns but not cleanly, this starts to wet the plugs and it gets worse and worse until you change out the fuel. So that's what I am going to do next. Not overly looking forward to it as from memory, the drain in the tank sump took a bit of sealing when I fitted it first time. Maybe I will syphon it out to save on that. Interesting other cars don't seem to suffer from the petrol going off as much, but I guess higher compression engines cope with it less. What does my V12 modern Aston Martin not suffer the same fate then? Presumably its ECU adapts the ignition timing to accommodate lower octane fuel? Oh the joy of classics, at least we have the time to play around at the moment. More later once the petrol has been changed.

[mgcjag]

Hi Andrew good idea syphoning....i once tried to undo a sump nut and the whole unit came away (it had rusted out)...best part of a tank full shot out in one go...lucky i was on the gravel drive.....Steve

[ralphr1780]

Andrew, the good news is that you still have your smelling senses , it is a good test to perform every morning nowadays.

[andrewh]

Hi Andrew good idea syphoning....i once tried to undo a sump nut and the whole unit came away (it had rusted out)...best part of a tank full shot out in one go...lucky i was on the gravel drive.....Steve

Its all brand new. Well it was all new 7 years ago and its only seen rain once! But I shall syphon anyway. Didn't have time today as I decided to mow the lawn. Well what else would you do when the weather was so stunning and the E type was calling for an Italian tune?

[andrewh]

Andrew, the good news is that you still have your smelling senses , it is a good test to perform every morning nowadays.

Ahha, yes I suppose it is rather good news considering!

[PeterCrespin]

What happened when you ran it with the resistor plugs?

I doubt it's the fuel gone stale in a new tank after only six months in a dry garage, in a temperate climate, especially since the car starts and runs.

[andrewh]

I did not run it Peter as I didn't want to foul up the new plugs. I can tell you now, fuel goes off within 6 months. The lawnmower service chaps will confirm that, but I dont need to have them confirm it. I have experienced it first hand many times. A well known Aston Martin specialist told me years ago that 99% of all cars coming into them with starting or running problems in the spring, all they do now is empty the fuel and clean the plugs and off they go again . Modern petrol is SH$T%E