You do know every trick in the book!
I have learned so much from you, Frank I will be forever in your debt. It’s people on this forum like you Frank, who have inspired us new to Jags to pick up a wrench / spanner and fix it. I’m not sure if you remember all of the posts with the Series II. All of the trials and tribulations I or we had with the SWB Series II ignition and fuel delivery problems. With out your help, I may have never got sorted.
Oh, one more thing. It was the '86 is the XJ with the ballast resister which is a Federal car sold in Eastern Washington (specifically Spokane WA). Easter Washington has freezing cold winters. The '85 is a Southern California car sold in Newport Beach CA.
Ballast to aid cold weather starting. I suspect Mark has misread the print. It does, but, in the opposite way. In some applications. Intended to allow cranking and delivering the full 12 to fire. Then back to six for run.
Obsolete on electronic ignition. Original purpose was to protecr the points in old tech point and condenser ignition.
The circuit was common in older 6 volt USA cars. Full 6 on crank and then 3+ on run…
jalopy racers on flat head v8 power often deleted the ballast and ran 6 v to race. Swapped in another distributor for the main event. Cleaning pints not an issue. resetting the timing was, But, that is another story…
Many on this forum have tossed the ballast things over the hedge a long time ago Frank has neatly described the function of them…
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Quite frankly, Mark - looking at the workshop manuals; I find neither rhyme nor reason in the variations of external resistor or no external resistor to the various coils, model years and geography…
I ‘thought’ that it was fitted to low resistance coils, but that was not it. My other thought was that it was fitted to restrict current flow through the ign amp - to protect it.
However, nobody has reported any ill effects by simply removing whenever found. And incidentally; a failed resistor sometime cause trouble and is removed by a PO - so a missing resistor doesn’t prove factory set-up. Or the other way around…?
Does the training manual have a publication number? I’d like to find one for myself.
FWIW, there’s a TSB describing the addition of the ballast “to improve ignition performance” but nothing more specific than that, at VIN 421xxx (or something like that), which would towards the end of 1985 model year. Other than that the use of the resistor isn’t clear, as Frank mentioned
A low battery charge will hurt starting performance, yes. If the battery is a bit weak there isn’t enough oooomph to turn the starter and properly power-up the fuel injection. I discovered this quite by accident many many years ago. I was pulling my hair out trying to diagnose an ‘extended cranking time’ problem. Long story short, a new battery fixed it completely.
I looked at it again last night, and the ballast stuff was for the OPUS 3 ignition . As one of my earlier employers would put it, “Hey Lee! WRONG AGAIN.” I really need to learn when to keep my mouth shut – or in this case, just stop typing.
ANYWAY
The way I understand how a resister works is, when the resister is cold, there is little to no resistance; so the ignition gets the full battery voltage – but the current is smoothed out a bit as the electrons are kinda waiting their turn
to go through the resister – for a consistent 12v. As the resister heats up from the electrons passing through it, the electron’s bunch up while waiting their turn to pass through the resister. This is when the resistance comes into play.
I’m guessing the early electronic ignitions were rather sensitive, like points, on how much voltage is actually passing through the system
Thanx Doug (and Frank) for setting me straight. I’d hate to mislead any forum members.
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While heat does increase resistance, Mark, in any thing carrying current - but it has nothing to do with deliberate control of current flow.
Crudely; while unwanted, the increased resistance due to heat does not alter the operation of components - but excessive heat itself may destroy components…
The way I read it, this was by design.
A cool ballast resister offers little to no resistance, providing full battery to the coil, once the engine starts and a bunch of electrons start flowing through the ballast resister, then it heats up, which imposes the “measured” or designated amount of resistance. which protects the coil, amplifier module, & pick up from also overheating. Especially the ignition module. More succinctly put, Functioning by design.
That was paraphrased out of the Lucas Electronic Ignition training handbook.
and once again you are right, unless it’s edible, cooking components is all bad.
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Oh no, Mark - the coil resistor provides its specified resistance at all times, with little variation with temperature…
As an aside; in the Opus system a set of resistors were used to control voltage to the coil and ign amplifier in rather complicated way.
When used on mechanical points an external coil resistor was used to protect the coil if ign was left ‘on’ without the engine turning. Such a resistor was simply bypassed in ‘crank’ to give battery voltage to the coil…
On the S3 CE system the coil resistor is permanently in line, limiting current without controlling it…
Ie; a 1 ohm resistor has one ohm resistance cold… and about ditto hot…
Note, however, my '86 XJ6, though built in July 1985, sold new in Southern California in August 1985, and did come with a ballast resistor. The coil had a green 'Jaguar; sticker with gold letters. When I replaced it several years ago with a Lucas coil from SNG Barratt,I peeled off the sticker for curiosity and found a red white and blue sticker hiding underneath, I cannot remember the name. The molded plastic front of the coil upon which the plug leads mounted has the name ‘Ducellier’ in raised letters. Since my car was an ‘early’ '86, it wouldn’t be implausible to surmise that later '86 cars were no longer fitted with the ballast resistor.
What was the end result of you hard cold start? I’ve been down those rabbit holes on both of my XJ6’s '85 & '86. At the time I was positive it was a fuel issue - my lighted HT Lead lit up so there was energy going to the plug. Yep, enough to light the light but not the plug.
The last two videos I did on my YouTube Channel, Jag Mods are both ignition related. Maybe it will help.
In my case, the '86 wouldn’t start because the ignition amplifier and cable were cooked. replaced the coil and amplifier with MSD street performance upgrades. I’m not 100% sure how much of an “upgrade” it is from the stock, but it came with cool stickers AND it fired off almost immediately and idles silky smooth.
However, once I got down the road and decelerated, the pig quit. I couldn’t get to start for nothing. There’s a thread a year or two back that covers this topic… anyway. The intake timing change was loose so the cam would adjust and retard itself independly of the exhaust & crankshaft. picked up the slack - runs great! starts first bump just about every time. Just about because it sits more than it’s driven.
Hi Mark
Changed the battery and so far no problems .I used a Stop Start version of the battery that has a higher cranking value, (stop start batteries are used for cars that have a stop start system ,that stops engine when stationary and restarts when you depress clutch).
So it looks as if Aristides was spot on in his first posting! But maybe you report back after a few charging cycles. I’m a bit surprised that a stop-start battery fitted into you battery compartment and the stock alternator is powerful enough to keep it charged.
Why? It‘ll be comparable in size and power need, but is designed for frequent starts and higher charging rates.
The start-stop battery in our new mx5 is tiny. Closer to a motorcycle battery than to a decent car battery. I didn’t believe my eyes when I first saw it.
Naturally, bigger should be better. There is no reason the alternator would have to work harder; power use is the same and voltage too!
I think the start stop units are mostly more heat resistant and AGM type. Who knows what else makes them so expensive, but they must hold up better.
