Lotus Elan

Strange ignition problem

PostPost by: Rokkbert » Wed Mar 18, 2015 7:52 am

So here's my problem,
There isn't a fuel delivery problem and I do have spark (albeit slightly weak), and when the car is running it idles and revs perfectly. However, it seems as if when the key is turned to the "run" position, it is only engaging the starter, and not sparking. The only way to get the car to start is to quickly let go of the key and hope that the engine has enough residual energy to let the ignition system kick in. I have bench tested the ignition switch and it checked out fine so I'm running out of ideas. The coil does have an internal resistor and I'm getting a lower voltage than the full 12 volts so I figure there must be additional resistance somewhere in the circuit, but I have a feeling that isn't my only problem. Any light someone could shed on the situation would be much appreciated. :)

I would like to add that this is a father son project and I am currently learning, so any technical mistakes I have made I apologize for.
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PostPost by: gus » Wed Mar 18, 2015 10:55 am

DO you have a ballast resistor?

Ignition switch?
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PostPost by: Chancer » Wed Mar 18, 2015 11:07 am

You have a ballast resisted coil and the problem is that it is not being bypassed by a direct 12v feed when cranking.

You can prove this to yourself by hotwiring the coil and the engine will burst into life while cranking, dont let it run for any more than a few seconds as the coil will overheat, usually takes 5 minutes or so.

There should be a terminal on the solenoid that produces the 12v direct to the coil SW terminal, has the wire come off,? have you changed the solenoid for the wrong type?

Check that 12v is present at this terminal when cranking then trace the wire to the coil.
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PostPost by: billwill » Wed Mar 18, 2015 1:27 pm

Answer withdrawn as I'm not sure that what I said was right.
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PostPost by: Rokkbert » Wed Mar 18, 2015 4:12 pm

As far as I know the solenoid is the original solenoid. I also have a non resistance coil that isn't currently in the car, so the one in the car is a ballast resistor coil. When cranking it's only getting about 8.7 volts. Would that be enough to cause this problem?
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PostPost by: Rokkbert » Thu Mar 19, 2015 12:17 am

Put in a coil without a ballast resistor and it fired right up. I'll try to start her up tomorrow just to make sure that it isn't intermittent but it seems like that's solved it.
Thanks all,

Robert
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PostPost by: denicholls2 » Fri Mar 20, 2015 3:40 pm

Concern: You may have had two ballast resistors in play (the external and the internal) and that was your problem. On the other hand, if you've eliminated the ballast resistor entirely then your coil will be short-lived. :shock:

What you want is for the resistor to be in play when the car is running but not when it is starting.
- If it's in play when starting, you'll need more power to start
- If it's not in play while running, you'll burn up the coil.

Good to hear your starting problem is addressed, make sure you don't now have a coil burning up problem.
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PostPost by: KevJ+2 » Fri Mar 20, 2015 3:58 pm

Hopefully Robert's problem is solved, but I have a related query.
I have TT electronic ignition (distributor) and Lucas 12 volt coil (no ballast), so black and red from dizzy to coil and Red/Green from the tacho (68+2). I have a Wosp pre-engaged starter so I've removed the old solenoid and wired White/Red to the starter solenoid.
Should I take an extra lead from the starter solenoid to the coil for cranking or will the three wires be enough?
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PostPost by: Rokkbert » Fri Mar 20, 2015 7:55 pm

I've been periodically checking to see if the coil is getting hot and so far it's fine, my best guess would be that somewhere in the new wiring harness there's a resistance wire.
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PostPost by: Grizzly » Fri Mar 20, 2015 9:12 pm

Just check the Coils resistance, if its around 3ohm its a 12v if its lower say 1.6 its a 6v

If it turns out to be a 6v it will burn out quite fast with a direct ignition feed, i think if it was me i'd check the power to the Balist is coming on with the Ignition and the 12v feed is working when the Ignition is engaging the starter only. If that's working there you will get an easier starting car if you stuck with that system (assuming the wiring is there for it)
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PostPost by: billwill » Fri Mar 20, 2015 10:13 pm

KevJ+2 wrote:Hopefully Robert's problem is solved, but I have a related query.
I have TT electronic ignition (distributor) and Lucas 12 volt coil (no ballast), so black and red from dizzy to coil and Red/Green from the tacho (68+2). I have a Wosp pre-engaged starter so I've removed the old solenoid and wired White/Red to the starter solenoid.
Should I take an extra lead from the starter solenoid to the coil for cranking or will the three wires be enough?
Kev.


It is not simply an extra lead, it is an extra contact on the solenoid, which is only live with battery voltage while the solenoid is activated and is isolated at other times.

Without that isolation (say you connected the coil to the starter activation contact) there would be a back feed from the coil to operate the solenoid, so the starter motor woud run all the time.

Similarly if the ballast bypass circuit runs from the ignition switch, it must be an extra contact on the ignition switch which is isolated in all but the START position.

If your solenoid does not have the extra contact you could wire a relay coil in parallel with the solenoid and then use the switched contacts of the relay to provide the ballast resistor bypass.

It could perhaps be done with a diode instead, but then you lose about 1.5 volts accross the diode during starting, so the statring boots will not be so good.
Last edited by billwill on Sat Apr 11, 2015 8:07 pm, edited 1 time in total.
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PostPost by: KevJ+2 » Sat Mar 21, 2015 11:22 am

Thanks Bill, good point about the back feed, I didn't think about that but my knowledge is quite limited.
I think the easiest solution is for me to take a supply from the starter position on the ignition switch and I do like the relay idea.
What fuse rating do you think I need for the coil supply?
Thanks,
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PostPost by: billwill » Sat Mar 21, 2015 9:14 pm

KevJ+2 wrote:Thanks Bill, good point about the back feed, I didn't think about that but my knowledge is quite limited.
I think the easiest solution is for me to take a supply from the starter position on the ignition switch and I do like the relay idea.
What fuse rating do you think I need for the coil supply?
Thanks,
Kev.


The Start-position contact on my Elan starter switch is not isolated (it's connected to the solenoid activation terminal), so you can't use that directly, you still need a relay to get the isolation.

Elan's built with a ballast resistor might have a different ignition switch, but it is more likely to be a different solenoid, (one with an isolated contact), I think.
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PostPost by: billwill » Sat Mar 21, 2015 9:22 pm

I don't know about what fuse rating is needed for the coil, It only uses an am,p or two to generate the sparks, so logitally a 15 or 20 amp fuse would be more than adequate, but then I think that on the standard S3 there is no fuse at all on the ignition circuit, so I just don't know.

It's not somewhere that you would want an unreliable fuse holder; it's max average current woulfd be at full revs, so if you were zooming along the motorway at 70 MPH (?) you woul really, really not want an ignition fuse to blow and stop your engine.

Been there, done that, when the cambelt broke on my old XR2...It's hairy getting to the hard shoulder under those conditions.
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PostPost by: stugilmour » Sun Mar 22, 2015 2:47 pm

Rokkbert, is it still working properly?

I had the same issue on my car before and after a total rewire including conversion to electronic ignition, removal of solenoid, new coil. The ignition switch was not working correctly in the 'start' position, but worked correctly in the 'run' and 'accessory' positions. The mechanic that was doing final commissioning cleaned the ignition switch, but it only worked for about three months or so. Replaced the ignition switch and big bubbles, no troubles. Intermittent issues are the worst! :)

HTH

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