Author Topic: Ignition System  (Read 6463 times)

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Offline 3929R

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Ignition System
« on: Tuesday,September 25, 2012, 04:26:07 PM »
I haven't owned a vehicle with a carburetor and more than one cylinder for several decades....  my relearning/ learning curve is steep and I'm stuck...

My starter died a slow death last month.  I replaced it and now the car turns over fine but won't start  :huh:.  I do not think the new starter or dead starter are related to my current problem.  The car started running rough and stalled at idle immediately (<5 minutes!) before I parked it and ordered the new starter.  It had also unexpectedly cut out/ died once at freeway speeds and then just as unexpectedly restarted (push/bump start) on the off ramp.  Otherwise the car was running great just 5 minutes before parking and ordering  the new starter.

Mine is a 73 TCS that matches this wiring diagram- http://www.lotus-europa.com/manuals/misc/electrical/tcsearly.gif It has a Mallory Voltmaster Mark II ignition coil (aka cold start coil) with external ballast resistor.  It has a Lucas distributor (stock?).

Observations:
-All plugs look a bit carbon fouled (I hope to get new plugs tomorrow*).  I think a result of repeated unsuccessful attempts at starting and not cause of not starting?
-Timing light suggests that all plugs wires are getting some voltage (enough to trigger the timing light to flash).
-Visual inspection of distributor rotor and cap looked ok.  (How do I get to the points?).
-White wire on ballast resistor is getting hot enough to melt the insulation (wire that runs to tach).
-Tach seems to only work when starter is engaged???
-New gear-reduction starter required combining the two wires connected to the solenoid (one spade terminal on the new starter, two on the old).  I did this per info on the knowledge base and think it is correct, but....
-I don't think it is a fuel problem.  This is based on the sudden onset and fact that a dose of quick start into the intake plenum has no effect.

Any ideas, suggestions, or disparaging remarks on how to proceed?

How do I test the coil and resistor?  Any suggestions for an ignition coil and/or resistor?   On my current resistor the wire to the tach (see right wire in pic below) is on a round button shaped thing.  Is this a second resistor and could it cause the hot connection?

*I'm having a hard time finding NGK BPR7ES plugs.  Any other suggestions?

Sincerely,
Europa Knob
Mark
Salt Lake City, Utah, USA

Offline EuropaTC

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Re: Ignition System
« Reply #1 on: Tuesday,September 25, 2012, 11:32:02 PM »
Hi,
Well, I'll start off by admitting I have no idea about the Mallory coil you have there, or how it should work. But I'll start the ball rolling with a few ideas and maybe someone with more knowledge will pitch in later on.

1. I'd never rule out fuel on a car that's been standing, UK fuel seems to evaporate very quickly these days and leave gummy deposits around to block up jets. Having said that though, from you description of sudden cutting out, tach problems, etc, it does sound more ignition related than fuel.
2. Sooty plugs are normally over-rich mixtures but I guess could be attributed to irregular firing or random misfires. I use a little gadget that goes between the plug cap & plug and which makes it very easy to see if everything is working consistently.  (pictures below)
3. I don't like the sound of those hot wires, that looks wrong.  Especially if the tach stops working when the ignition fires up, there's a mis-match somewhere.  I found Voltmaster instructions on the web but can't use a pdf attachment here so I've just copied the wiring diag. My first thoughts are to check it's correct & re-make the joints on the car. There are comments about using carbon cored leads, don't know if that's significant or not but it is mentioned.
4. CB Points, ah one of the joys of the Lotus engine (or not !).  It is possible to adjust the points in-situ, but access is terrible and as you grow older, I can tell you it gets even worse. These days I tend to remove the distributor completely, drastic but at least you know it's right afterwards. I jack up a rear wheel, put the car in gear and set it to TDC on #1 firing stroke. Remove the distributor using the single bolt holding the clamping plate to the block so you don't disturb the timing. After that amount of hassle I just replace the CB points, condensor with new ones & re-assemble. (If you haven't done this trick yet, there are instructions in the manual on how to set the rotor/distributor so the gears mesh correctly and retain the timing when you insert the distributor to the block - ask if you haven't got them)

Plugs - I'm about to try some NGK 6ES grade plugs instead of the usual 7ES. I do short trips and apparently some folks on the Elan forum say these work better under such conditions with smoother running and less fouling.  (they are slightly hotter) If you can get these instead then they should be good enough to tick the "replaced plugs" box for now.

Brian
« Last Edit: Tuesday,September 25, 2012, 11:34:29 PM by EuropaTC »

Offline 3929R

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Re: Ignition System
« Reply #2 on: Wednesday,September 26, 2012, 10:08:44 AM »
Thank you Brian.
1.  As you suggest, I have not ruled out fuel but the car was has not been parked very long.  At least it was not parked long this time.  It was however in storage from 1993 to spring of this year.  I did drain the tanks, replace fuel filter, go through the fuel line, clean carbs, etc.

2.  I previously did not notice any misfiring, hard starting, or hesitation.  So, I thought the carbon on the plugs could be due to the engine not starting and thus the plugs never getting hot enough to burn off the carbon?  Does this make sense?

I will look for some plug testers.  Do your plug testers show that some voltage is getting to the plugs?  If so, I think I accomplished the same thing by using my timing light (not for timing but to see that there is at least some voltage on each plug wire (enough to trigger the light).

3.  Thanks for that Voltmaster diagram.  Based on it and the parts diagram, I think the button shaped thing that at the wire to the tach is on may be is the factory "ignition resistor"?  If so it looks to be wired according to this and the Europa diagrams (plus I have not changed anything since it ran well).  The spade connector was loose so I  tightened it with a pair of pliers and doused it with DeOxIT.  I need to double check to verify that it is still getting hot. IF THIS IGNITION RESISTOR HAS FAILED, COULD THAT EXPLAIN MY SYMPTOMS?

4.  I need to check the points.  But if I'm going through the trouble of removing the distributor, perhaps I should just convert from points to a Pertronix electronic ignition?
« Last Edit: Wednesday,September 26, 2012, 11:14:03 AM by 3929R »
Mark
Salt Lake City, Utah, USA

Offline 3929R

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Re: Ignition System
« Reply #3 on: Wednesday,September 26, 2012, 12:21:21 PM »
Ah hA!  (I think)
"Post from Roger is correct EXCEPT that original ballast resistor on TC was attached to the top of the coil, so if you remove the wire and check it's voltage to ground, you will get full battery voltage. If you check bottom lug of resistor where it bolts to coil you will see reduced voltage (or no voltage if it is cracked.) There is a strong possibility that an older TC ha a non original ballast resistor placed in a location remote from the top of the coil as these did fail and were hard to find. If the ballast resistor fails, the car will fire while the starter motor is running but the engine will die when the key is returned from the start to the on position. Again, the original resistor was (at least on my car) green and black, about the diameter of a quarter and about 3/16" thick.....Dave"
http://www.lotustalk.com/forums/f120/ballast-resistor-twin-cam-ignition-system-106088/
Mark
Salt Lake City, Utah, USA

Offline EuropaTC

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Re: Ignition System
« Reply #4 on: Wednesday,September 26, 2012, 01:43:57 PM »
Amazing thing this interwebby wotsis, isn't it  :)

I can't really help on ballasted ignition systems, I know the theory but my cars have usually been simple 12v coils and they've usually worked well enough for me not to bother about a ballasted system. In fact my first thought on seeing the Mallory coil was to buy a simple 12v one and see how that went on.

The plug testers offer nothing more than your timing light apart from convenience. Over here you buy a pack of 4 for £6-ish ($10 ?) which allows you to plug in 4 at once and see what's happening across the engine at one go, rather than moving a timing light one at a time. (they also give a nice, warming, red glow in the cam valley ;) )

I agree with you on the plugs. That would be my take as well given the work you've done cleaning out the system when re-commissioning the car. (I was lazy, I only did the carbs & petrol pump ! )

Pertronix, yes, lots of folks go that way and in fact I've got one fitted to my Elan. It works really well but I've also converted the rev counter to modern internals, whereas the Europa still has the old Lotus rev counter.  I'm reluctant to experiment as there are tales of rev counter problems with modern electronic ignitions and for the mileage I do in the Europa I might as well stick with CB points. If anyone can confirm the Pertronix doesn't affect the OEM rev counter I think I would install one because it has made starting much easier.

Offline 3929R

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Re: Ignition System
« Reply #5 on: Wednesday,September 26, 2012, 08:36:21 PM »
I installed a new generic ballast resistor from the local generic auto parts store and the car almost started before I could turn the key.  I also put in new plugs for good measure, though I really think the old ones would have been fine.  Just to double check, I reinstalled the old button resistor and it would not start. 

It now idles well but has sever hesitation with throttle.  The new resistor is also very hot and the tachometer (rev counter) does not work when the key is in the on position (works when starter is on) .  I wonder if the generic resister has too much resistance?  The old defective resistor measured 5 ohms.  The new resistor measured 2 ohms but is speced at 1.4 ohms. 

SO how many ohms is the original button ballast resistor supposed to have???  Anyone know?  The Lotus wiring diagram doesn't even show this resistor as it was attached to the original ignition coil.
Mark
Salt Lake City, Utah, USA

Offline EuropaTC

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Re: Ignition System
« Reply #6 on: Thursday,September 27, 2012, 12:39:35 AM »
I can't help you with the OEM spec for the ballast resistor I'm afraid. However, this rev counter problem is intriguing.

First point - has it ever worked properly while you've owned the car ? I'm curious if it's a recent fault or you got the car with a non-working tach along with that coil wiring set-up.

Looking at the wiring I can't help but think it's something to do with that Mallory coil. On the info I found it shows two resistors in series, again, that's a new one on me with the rev counter shown as wired through the second resistor. Why 2 ? 

The other nagging suspicion I have is that one sign of a coil (or CB points condenser ?) breaking down is failure at higher revs even though idle is ok, although I accept that won't explain the rev counter issues.

With all that in mind I think I'd be tempted to try another coil. If you decide to go for a pertronix set up then I'd also change the coil for a new one with a known resistance & performance so a new coil wouldn't be money wasted. And in the grand scheme of things, a new coil is pretty cheap compared with normal Lotus parts !

Brian

Offline 3929R

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Re: Ignition System
« Reply #7 on: Thursday,September 27, 2012, 10:07:48 AM »
The tach worked fine before (though it had randomly cut out once or twice) so this set up can be effective.  I've been considering the possibility that the resistor is a symptom but not the disease.  However, the tach wire attached to the new one is still overheating.  Ballast resistors at Summit Racing range from .25 to 1.8 ohms, suggesting that 5 ohms (old resistor) and 2 ohms (new resistor) may be too high.  I think the hot connection is best explained by too much resistance in this resistor?  I think too high of resistance would also explain the tach.  But I suppose a failing coil could also increase the resistance and maybe the lead from the tach is just the point that gets hot?  For that matter I suppose the second resistor (I think it is a Mallory resistor) could cause these problems?  Seems I need to check the resistance on the coil and second resistor.  If they are as specified, I may try a 1 ohm ballast resistor and if that doesn't work, give up and install a new coil (with our without a new coil).

As for the 2 resistors wired in series, the diagram shows this set up is used only with an ignition system that uses points.  I'm guessing that without the extra resistor the coil could cook/ark the points?
Mark
Salt Lake City, Utah, USA

Offline LotusJoe

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Re: Ignition System
« Reply #8 on: Thursday,September 27, 2012, 10:40:35 AM »
Guys, I'm fairly certain that the tach wire goes to the negative side of the coil. Otherwise the tach can not see any pulse, only a constant 12 volts. I can't confirm that with any of the wiring diagrams as they are unclear as to the connections at the coil, but in almost every instance I've had with tachs, that has been the case. Is there any additional wiring information on the the Malory ignition?
Joe Irwin
3927R TC Special
(The Classic Barn Find)


Offline 3929R

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Re: Ignition System
« Reply #9 on: Thursday,September 27, 2012, 04:06:31 PM »
Guys, I'm fairly certain that the tach wire goes to the negative side of the coil. Otherwise the tach can not see any pulse, only a constant 12 volts. I can't confirm that with any of the wiring diagrams as they are unclear as to the connections at the coil, but in almost every instance I've had with tachs, that has been the case. Is there any additional wiring information on the the Malory ignition?
I don't fully understand how the tach works but it is wired to the + side of the coil. This is how my car is wired.  This is what the Mallory diagram shows (though it does not specifically show the tach).  This is what the Lotus diagram shows, though it is not very clear on this diagram... the tach wire is shown on the same side of the coil as the white w/ yellow wire that goes to the starter solenoid (the extra circle on the cold start coil is indicative of the ballast resistor)... the other side of the coil (white w/ black wire) goes straight to the distributor.
Mark
Salt Lake City, Utah, USA

Offline LotusJoe

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Re: Ignition System
« Reply #10 on: Thursday,September 27, 2012, 06:38:07 PM »
I agree the wiring diagram is less than clear. However in this case I suggest we ask someone with a stock TC to go check the color of the wires going to the coil.


Joe Irwin
3927R TC Special
(The Classic Barn Find)


Offline EuropaTC

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Re: Ignition System
« Reply #11 on: Thursday,September 27, 2012, 10:27:30 PM »
I agree the wiring diagram is less than clear. However in this case I suggest we ask someone with a stock TC to go check the color of the wires going to the coil.

Ok Joe, when I've come to life and had my second cup of coffee, I'll take a look at mine. It doesn't have the ballast resistor on the coil but it does have the OEM rev counter.

Edit to add; well, I've had a look and it's no help at all to this one. 2 wires, one going directly from the -ve terminal on the coil to the distributor, the second on the +ve coil terminal and going to the ignition circuit. Clearly the rev counter can't be on the -ve coil side, it's a direct line about a foot long, so presumably there is a joint splicing it into the +ve connection somewhere inside the car. 

When I look at the Lotus wiring diagram it looks as if ignition wiring goes via the tach to the (single) ballast resistor, so presumably going through 2 resistors isn't what it was designed to do ?

The wiring anomalies might be down to the way these old tachs operate. I replaced the internals of the Elan tach with modern electrics last year and that's wired exactly as you say Joe, with a wire to the distributor side of the coil to sense the pulses, an earth & a +12v feed.   

I picked up these scans a while ago that someone posted to illustrate the differences between the various Smiths' tachometers and as you can see they have both wiring versions !
« Last Edit: Friday,September 28, 2012, 01:05:41 AM by EuropaTC »

Offline LotusJoe

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Re: Ignition System
« Reply #12 on: Friday,September 28, 2012, 10:33:05 AM »
WOW, interesting wiring setup on the vintage Smith gauges. Now I'm not sure at all. It does in-fact look like the Tach wire goes to the positive side of the coil. I unfortunately or fortunately removed the stock wiring harness from my car during my restoration and put in a GM type harness from Centech so I can't verify anything. I think all I've done here is add to the confusion  :confused:   
Joe Irwin
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(The Classic Barn Find)


Offline 3929R

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Re: Ignition System
« Reply #13 on: Friday,September 28, 2012, 10:36:48 AM »
No worries LotusJoe.  All input is good.

This doesn't help with the tach wiring, but it does show what the original "button" ballast resistor looks like.  It is attached to the right coil post in this drawing.
http://www.lotuseuropa.org/images/WorkshopManual/PartManual/tcm.pdf
Mark
Salt Lake City, Utah, USA

Offline EuropaTC

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Re: Ignition System
« Reply #14 on: Friday,September 28, 2012, 10:58:19 PM »
Ping ! that's the sound of a light bulb coming on....   my car had one of those when I first got it,  I remember now, it's all slowly coming back. 

After seeing that page I vaguely remember thinking "that coil operates on a lower voltage than my other cars, I've never had one before and my spares are normal 12v coils so I'll change it now".  It was all corroded and I expected it to pack in as I drove the car home,  so that's how my TC came to have a conventional 12v coil in there.  Funny how a picture triggers the old grey cells into life.

So my comment now would be to simply buy a 12v coil (one of the Pertronix ones if you like) and forget the ballasted system. A cheap fix, less components to go wrong, no wiring issues, another box ticked on the "it can't be that" list.  ;)

Brian

ps - no Joe, it's impossible to add confusion to these cars.....   40+yrs old, several DPO's all tinkering away and above all the Lotus were well known for using whatever parts came to hand to get them off the production line !