Overheating coil?

[64etype]

I believe, if I have read the posts correctly, that the push button cars didn't have ballast resistors anyway.

No, they did not. But it's a consideration if someone retrofits an electronic points system that happens to require a ballast resister (as I did), or wants a better starting points system like in the later S2. I believe you said you are changing to a push button start arrangement...

[Philwesty]

Glad I started this thread - seems to be challenging thinking all round!

So... i replaced the Viper Dry coil which was originally suspected with a Lucas sport one. No difference in the readings - ohms, volts in and out etc. BUT, the missfire is definitely worse with the new coil. Now almost as soon as its up to temperature it starts missing - then it stops altogether.. a new turn.

Checked fuel pump is active since it seems like fuel starvation now.. changed rotor. no difference. ordered new plug leads (have original caps on my leads) dizzy cap and rotor AND new electronic dizzy sensor - all from SimonBBC.com so its Powerspark stuff.

If its stops raining long enough i will replace one bit at a time report.

P

[Hugo]

With all this debate about relays and resistors, I had lost sight of the original problem. It's frustrating, isn't it, when you have only a limited number of possibilities on what is a very simple fuel and ignition system, yet it defies resolution.
Going back to the relay issue for some final thoughts, let me repeat my thanks to Eric in Texas for pointing out what should have been obvious to me but wasn't, and explaining why they fitted a relay. It occurs to me that this chimes with Jaguar's efforts to keep costs down. When they began fitting resistors, I think what they should have done was re-design the ignition switch so that it had two independent contacts in the 'start' position; one for the starter and one for the coil. But it was obviously cheaper to fit a relay so the two circuits didn't see each other.
Finally, I find the psychology of this whole relay/resistor debate quite interesting; while we were all scratching our heads before Eric shed some much-needed light on the subject, the consensus on this forum was that 'Jaguar must have fitted the relay for a reason', and leave it at that. Maybe I'm just an awkward bugger, but I found that unsatisfactory. In fact I'm surprised that anybody with an enquiring mind would be satisfied with that answer. Now we all know the reason, however.
All we have to do now is figure out what's wrong with Phil's car.

[Hugo]

I believe, if I have read the posts correctly, that the push button cars didn't have ballast resistors anyway.

No, they did not. But it's a consideration if someone retrofits an electronic points system that happens to require a ballast resister (as I did), or wants a better starting points system like in the later S2. I believe you said you are changing to a push button start arrangement...

Yes, I hope to run with a push-button start and without a resistor. If it proves difficult to start I might have to fit a resistor - and of course a relay to by-pass it!
In the old days, Ford used to fit ballast resistors on things like the Anglia. They were a real bugger to start, even with a resistor. Yet the equivalent Morris range didn't need a resistor. I never did like Fords.

[mgcjag]

Hi Hugo.....So why do you think they fitted a starter relay on all the earlier S2 cars befor they fitted a ballast Cct ....Steve

[Hugo]

I have no fecking idea - ask Eric!

[Hugo]

You do realise you've ruined my whole evening with this Steve - just when I thought we'd got to the bottom of it all, we're back to square one! I was about to go and measure the current drawn by a starter solenoid, just out of curiosity, but the heavens have opened so I'm stuck indoors watching the exciting election results instead.
I beleve somebody said the Series I had a different relay from the Series II; the later set-up (with resistor) has a relay that joins three wires together when activated; the main feed from the battery; the feed to the starter solenoid, and the feed to the coil. The Series I relay merely takes the load off the push-button starter switch to activate the starter solenoid. I don't see why it is needed, but I may be under-estimating the current drawn by the starter solenoid or over-estimating the capacity of the push-button switch. If they had put the relay next to the battery or to the starter solenoid it would have made more sense by reducing voltage drop, but putting the relay near the starter switch seems pointless.
Oh well, tomorrow's another day (and maybe another government?).

[JagWaugh]

...snip
When they began fitting resistors, I think what they should have done was re-design the ignition switch so that it had two independent contacts in the 'start' position; one for the starter and one for the coil. But it was obviously cheaper to fit a relay so the two circuits didn't see each other.
...snip

Purely conjecture, but I suspect what happened was somebody from marketing said "We need to fit an ignition switch like the Americans have to help us in the US market. Introduction in the next model year." and the electrical guys looked at what Lucas had available and discovered that the contacts wouldn't handle the load, so they asked permission to increase the cost of building the cars by 1 foot of wire and an additional relay and pointed out that this cost could be ameliorated by changing to a coil and resistor combination which was 0.02p less expensive than the existing coil. After long deliberation the cost increase was approved.

[Hugo]

Ballast resistors were quite common back in the 60's. If a Ford Angila had a switch that could operate a ballast resistor, you would think Jaguar could manage it.
One thing I've never heard is any complaints about poor starting from the non-resistor E Types. So why did Jaguar decide to fit one? If there was a need for a resistor, why isn't everybody retro-fitting them to the earlier cars?
Or was it indeed just cosmetic - a sop to the American market? In which case all the more reason to rip the things out and throw them away. Along with the relay (no, don't start that again!).

[JagWaugh]

Or was it indeed just cosmetic - a sop to the American market? In which case all the more reason to rip the things out and throw them away. Along with the relay (no, don't start that again!).

Not necessarily a sop. Think about the North American climate... A large part of it includes winter temps of -20C and lower. When you shop for a battery in Canada your eyes are on the CCA... the COLD Cranking Amps.

When I was growing up in Toronto ALL of our cars had plug in block heaters. This wasn't to make the car comfy when the temperature was low, it was because without them you'd really struggle to get the bloody car started after a night of -15. None of these cars had ballast resistors (they were all British). Everyone else had American cars... they didn't need their block heaters until it was -20.

Iirc a Battery that's at -20 will voltage drop more (and sooner) than at 0, and the oil is thicker which also adds to the load (and therefore voltage drop) while cranking the cold engine.

The ballast resistor helps in this situation. When it was -15 and you'd forgotten to plug the block heater in the car would often turn over almost decently, but it wouldn't fire. The solution was to use a 2nd car and boost cables - this would make the starter turn faster, but it also ensured that the voltage to the ignition was high enough to get a spark.

[Hugo]

Good point.

[Philwesty]

So today i replaced the electronic trigger, rotor, cap, HT+LT leads. New coil last week. plenty of fuel getting through.
Runs like dog when warmed. great up to that point. Idle ok when hot but misfire under load and then just stops. leave it a few minutes and then it'll start and run for 30 secs before the missing starts again.
Will to live lost. Runs worse than it did with all the old electrics on it.
Thinking of doing an engine swap with the Citroen as that's incredibly reliable... if slow.

[mgcjag]

Phil...sent you a PM

[Hugo]

It's good that it's getting worse - should make it easier to track down. You seem to have eliminated all the possible causes, yet still have the problem. Frustrating, isn't it. I had a DB6 with a similar intractable fault - replaced everything numerous times but never really got rid of the problem.
Remind me what non-standard items you have? Electronic distributor, go-faster coil? What else?
Have you tried taking a wire straight off the battery to the coil + terminal? That eliminates a lot of stuff in the middle (although I don't really see how anything there can be responsible, but it's important to eliminate every item.).
Can't remember whether you have a ballast resistor? If you do, just by-pass it for now. The coil will over-heat eventually, but it will take a while to do so, hopefully long enough to determine whether bridging the battery directly to the coil has made a difference.

[johnetype]

The Series 1 cars had a push button to operate the starter motor solenoid. That push button switch could handle the current required by the starter solenoid and as JagWaugh says, Jaguar didn't add things that weren't needed so there was no starter relay.

For Series 2 cars the ignition switch gained an extra position used to start the car and the push button was removed. This ignition switch can't handle the current required by the starter solenoid so Jaguar had to add a starter relay. This relay was mounted inside the car at the bottom of the A post on the RHS.

For the late Series 2 cars a ballast resistor coil was added to improve cold starting - and presumably improve the very tight emissions performance. This arrangement also requires its own relay acting as a switch to apply 12 volts directly to the coil just during starting. Again, no doubt to save money, Jaguar changed the relay they had been using as the starter relay to a two switch relay, technically a 2 pole relay. This meant there were now two relays associated with starting but because they were both inside a similar looking package it can confuse the situation as there's still only one actual physical relay. At the same time the starter/ballast resistor relay in question was moved from inside the car at the bottom of the A post to inside the engine compartment on the bulkhead behind the brake and clutch pedal housing. So, those few Series 2 cars with ballasted coils have a different relay in a different position.

Ash, sorry I confused you by saying "remove the ballast resistor and associated relay" when I should have said remove the ballast resistor and associated wiring to the starter/ballast relay. You still need the physical relay to use one half of it to operate the starter solenoid. If however that relay ever failed in the future could could replace it with the simpler single pole starter relay.

Hugo, there's nothing to stop you changing a Series 2 car to push button starting and you could remove the starter relay as long as the push button switch you use can handle the current required by the starter motor solenoid. However, if it was on a late Series 2 that had the ballast coil arrangement you'd need to retain the relay for the one half of it that's still needed.

In summary, cars using the ignition switch to start need a starter relay simply because the switch Jaguar used couldn't handle the current on it's own. Many contemporary cars managed without a relay because they had an ignition switch that could handle the current on its own and the ballast resistor arrangement is an unnecessary complication to leave in place if you fit any form of electronic ignition.

John

[ralphr1780]

Phil, sounds evident bit did you check the ground strap engine-to-body is in good condition ?

[Hugo]

[quote="johnetype"]The Series 1 cars had a push button to operate the starter motor solenoid. That push button switch could handle the current required by the starter solenoid and as JagWaugh says, Jaguar didn't add things that weren't needed so there was no starter relay."
"Hugo, there's nothing to stop you changing a Series 2 car to push button starting and you could remove the starter relay as long as the push button switch you use can handle the current required by the starter motor solenoid. However, if it was on a late Series 2 that had the ballast coil arrangement you'd need to retain the relay for the one half of it that's still needed."


Thank you - the world once again makes sense! Everything you say chimes with my own thoughts. I couldn't figure out why a push button would need a relay to operate a solenoid - I'm relieved to learn it doesn't!
Mine is a US import with a ballast resistor. I'm not convinced it is necessary however, although I won't know until I see how it starts without it - and I am a VERY long way from that at the moment.

[Hugo]

Just out of curiosity I measured the current drawn by some coils - it's about 4 amps or just under. I thought it would be lower than that. An old Lucas coil gave 3.75, a Bosch coil gave 4, and an Intermotor one gave no reading at all, so that's now in the bin. Been on my shelf for years taking up space for nothing!
I also measured the current draw of the starter solenoid - it shot right off my 10 amp scale, and that's the biggest ammeter I have. It's a pretty chunky solenoid. Hence the relay! I'm sure a modern starter would draw a fraction of that.

[AshM]

Thanks for the clarity John.

You have to smile - that one sentence from you, prompted my questioning reply then results in pages and pages of wonderful interaction and knowledge sharing.

This is a great forum.

cheers

[Heuer]

Can I remind everyone that if you are going to use the "quote" function you need to ensure the text is prefixed with (quote) and suffixed with (/quote). It seems some people are deleting the suffix and it is making threads difficult to read.

So click on the quote button and make sure the text is bookended between the brackets. If in doubt use the 'Preview' function before posting - the quoted text will be in a yellow box.