Intermittent starting problem

[fireblade]

I have an intermittent electrical problem with my 1969 Lotus Elan SE. sometimes it starts on the button other times it turns over but no go. The car has been completely reliable up until now.i have narrowed down the problem to be power to the coil. I have replaced the coil thinking this was the problem only to find this was not necessary. (not thinking systematically).The ignition is Lumenition Magnetronic have checked plugs and leads and all ok. i pulled out the Rev Counter to check electrical connections. I understand the power supply to the coil goes via the rev counter (white cables?) Is this correct? I connected a 12 volt bulb across the + and - terminals on the coil to check for power. Car started fine yesterday and ran perfectly. This morning turned on the ignition and no power to the coil. It seems to have a mind of its own. I would be interested to know where the white cable on the coil + terminal that feeds into the harness goes to. Could I have a problem with the ignition switch? Out of interest the original coil that I replaced had ballast stamped on it so naturally I replaced it like for like but I cannot find the Ballast resistor.....how big would it be and where would it be located. Would it have left the factory with a Ballast coil.
The weather is warming up and I need to get out and make the most of it
Your help and suggestions would be greatly appreciated.

[gus]

try wiring an alternate power path to the coil temporarily

I have had the start position of the ignition switch get dicey and the car would crank and crank and fire as soon as you let go of the key.

[alan.barker]

I understand if you have a Ballast it is a round thing attached to the Coil.
Could the problem be the Switch inside the Glovebox
Alan

[ericbushby]

Find the white wire on the back of the ignition switch, pull it off and clean it. In my case the trouble was a corroded crimp on the wire at that point. I fitted a new tag and that cured it.
Please notice that nowhere have I said this is easy.
Yes, the ignition power goes to the rev counter before the coil. It counts the pulse rate.
Eric in Burnley
1967 S3SE DHC

[fireblade]

Thanks to gus Alan and Eric for a quick response. Just attempted to start the car and hey presto power at coil and it started instantly.
I did wire a alternate power supply direct to the coil and this worked.
There is no ballast on the side of the coil so either it hasn't got one or its hidden elsewhere. I do not have a cut out switch in the glove box only a heavy duty looking isolation switch under the dash on the drivers side well hidden and operates correctly.
I will try the white wire connection on the back of the ignition switch.This I think might be the answer to the problem might even fit a new ign switch as they are relatively inexpensive. The location of the switch looks a nightmare so I guess pulling the dash out forwards might help.

[denicholls2]

If the coil is marked "ballast" then it is highly likely it is internally ballasted and they are trying to tell you not to add external ballast (which would make for the condition you experienced if the bypass circuit for a stronger starting spark isn't working as noted above). You won't find the ballast bits unless you destroy it, maybe not then. Ballast is simply a resistor of the right size to de-spike the circuit. There are a lot of ways to make a resistor...

[nmauduit]

try wiring an alternate power path to the coil temporarily

I have had the start position of the ignition switch get dicey and the car would crank and crank and fire as soon as you let go of the key.

just in case it is of use to anyone :

I had a similar problem (intermittent absence of spark), only this would develop with some heat, that is after 5-10 miles : I found out eventually that it was the fuse box, one of the two circuits had copper fuse holder fingers that were not springy enough, and warmth made them too weak to stand engine vibrations.

[billwill]

If the coil is marked "ballast" then it is highly likely it is internally ballasted and they are trying to tell you not to add external ballast (which would make for the condition you experienced if the bypass circuit for a stronger starting spark isn't working as noted above). You won't find the ballast bits unless you destroy it, maybe not then. Ballast is simply a resistor of the right size to de-spike the circuit. There are a lot of ways to make a resistor...

Erm, its not there to de-spike the circuit but the rest is OK.

I had never heard of an internal ballast resistor but I looked and I found this interesting description & fix:


In the case of the internal resistor it relies on the fact that its resistance increases when it gets hot, thus reducing the coil current to its normal running value. When it is cold the resistance is lower thus feeding more current, more power, to the sparks when starting up.

In the case of an external ballast resistor it is in-circuit during normal running but it is bypassed on startup via an extra contact on the starter solenoid.


~~~~~
Some more articles: https://www.google.co.uk/search?q=inter ... gAaQt7_oCQ

[Quart Meg Miles]

In theory a ballasted coil, like the embedded one or normal external by-passed one, should run better at higher revs than a standard 12 volt coil due to a higher R/L value.

[fireblade]

Intermittent starting problem solved.
After spending hours trying to solve the mystery of the intermittent starting I have traced the problem to the small isolation switch located in the glovebox. I had assumed my particular car didn't have one so didn't think to look for this as I have a fairly heavy duty isolation switch mounted under the dash on the drivers side. So it pays never to assume anything. On pulling the cardboard glovebox out the switch looked well past its sell by date and about to fall apart. So the plan is to bypass this as I can't see the point of it and will leave the switch in place.
I am still not sure whether I have fitted the correct replacement coil. The original coil which I wrongly assumed was the cause of the starting problem was a Super Gold Ballast coil stating on the outside 'use only with 1.5 Ohms Resistance' but as previously stated I cannot find a Ballast Resistor anywhere in the car.So I Assumed the new replacement coil should be a Ballast type.
So the car is now running perfectly and runs with no problem.



.

[billwill]

Intermittent starting problem solved.
After spending hours trying to solve the mystery of the intermittent starting I have traced the problem to the small isolation switch located in the glovebox. I had assumed my particular car didn't have one so didn't think to look for this as I have a fairly heavy duty isolation switch mounted under the dash on the drivers side. So it pays never to assume anything. On pulling the cardboard glovebox out the switch looked well past its sell by date and about to fall apart. So the plan is to bypass this as I can't see the point of it and will leave the switch in place.
I am still not sure whether I have fitted the correct replacement coil. The original coil which I wrongly assumed was the cause of the starting problem was a Super Gold Ballast coil stating on the outside 'use only with 1.5 Ohms Resistance' but as previously stated I cannot find a Ballast Resistor anywhere in the car.So I Assumed the new replacement coil should be a Ballast type.
So the car is now running perfectly and runs with no problem.



.

If you run a coil that is designed as a ballast coil but you do it without a ballast resistor it will be overdriven and will probably burn out rather soon. Naturally you will have nice big fat sparks so the engine will run well.

However some Ballast resistors come in the form of a higher resistance wire in the loom instead of a copper wire, so that might be why you cant find it.

But if you car was designed for a ballast coil, i think that the solenoid should have an extra contact on it to feed the battery straight to the coil bypassing the ballast resistor during car-starting.