-ve Lead On Coil

[Guest TheDog]

i'm having problems that i thought was caused by the coil, but i have just replaced it with a new one and it still doesn't work. The coil is getting power through the +ve terminal once the ignition is turned, but i think there is a problem with the -ve terminals (I don't think it is earthing properly). I have 3 leads comming off the -ve terminal, 1 goes to what i think is something to do with the electric ignition and two go off into a wiring loom and i think they end up under the dashboard.

 

What is standard practice for the -ve leads, where should they go?

It used to work until a few days ago, when the engine just stopped working.

(p.s. it's a 2L pinto), whith an electric ignition.

 

Thanks for any help

Chris

[Guest Takumi]

i'm having problems that i thought was caused by the coil, but i have just replaced it with a new one and it still doesn't work. The coil is getting power through the +ve terminal once the ignition is turned, but i think there is a problem with the -ve terminals (I don't think it is earthing properly). I have 3 leads comming off the -ve terminal, 1 goes to what i think is something to do with the electric ignition and two go off into a wiring loom and i think they end up under the dashboard.

 

What is standard practice for the -ve leads, where should they go?

It used to work until a few days ago, when the engine just stopped working.

(p.s. it's a 2L pinto), whith an electric ignition.

 

Thanks for any help

Chris

 

 

-ve are normally earthed, might be that the coil is earthing through one of the other leads which inturn might not be earthing correctly. Best earth the coil directly to your chassis with a clean cable, making sure there is no surface corrsion where you attach/bolt it.

 

tk

[Guest TheDog]

Thanks, i thought it might be this but am a bit worried where the other cables go in case something else isn't working, but i will try this before i do anything else.

 

Is it standard for any other cables to come off the -ve terminal like on mine?

 

Thanks for your help.

[RedTrev]

Chris,

The -ve terminal of the coil is part of the low tension circuit and is connected to the electronic module and also to the instrument pack for your rev counter. It is not normally connected to ground/earth/battery negative.

 

Trev

[Guest MJThewlis]

What sort of ignition module are you running? I suffered a similar sounding issue when setting mine up with an ESCII ignition unit.

 

Whilst the coil is charged seperately it's the ignition unit that calls it to fire. My problem ended up being tied back to the power hold relay not coming in due to blown transistor on the board. The relay requires alsorts of signals in place to pull in automatically but a piece of fuse wire bridging the power across to ensure it has juice will at least help you to know where to start?

[Guest Tickton Paul]

Chris,

The -ve terminal of the coil is part of the low tension circuit and is connected to the electronic module and also to the instrument pack for your rev counter. It is not normally connected to ground/earth/battery negative.

 

Trev

 

Chris

 

Just wiringmy 2B with the ESCII module, the -ve of the coil does have 3 green wires coming from it, one goes to the ESCII module, the other two go to a bullet connector that connects to what I think is a supressor, see attached pic for clarification.

 

Paul

[Guest timswait]

The -ve lead IS NOT (permanently) connected to earth. It is switched to earth by the ignition amplifier, which is what provides the pulse to cause it to spark.

So if you're not getting a spark (check for spark at the coil rather than at one of the plugs, this eliminates the HT side of the dizzy and the plug leads), you are sure the coil is a good one, and you have +12V on the feed then the problem is that the coil isn't being provided with a pulse from the ignition amp. Probable causes of this are:

-faulty ignition amp

-faulty dizzy (the low tension side)

-fault in the wiring between coil, dizzy and amp

-fault in the power supply to the ignition amp (probably not if the power is being supplied to the coil OK)

[DAVE CASTLE]

I had the same problem it was the wire that goes to the starter motor from centre of module vicky green loom

Dave

[Guest TheDog]

Hi, thanks for your responses so far.

The joys of diagnosing a car you didn't build!

 

It also sounds like the wire that goes to the ignition is the key wire, do you know what the wires that go to the tachometer are for? Are they essential?

 

When testing the spark at the HT bit of the coil, how should i do this. Is the best way to just unplug the HT lead and look for a spark? Or use a volt meter? Sorry if this sounds dumb!

 

I don't think my 2 wires go into a surpressor (what does that do anyway).

 

I will take a look at the following things, but i'm not sure how to test some of them, is there an easy way to test

 

-faulty ignition amp

-faulty dizzy (the low tension side)

-fault in the power supply to the ignition amp

-fault in the wiring between coil, dizzy and amp (i should be able to do this ok)

 

Thanks

Chris

[Guest timswait]

It also sounds like the wire that goes to the ignition is the key wire, do you know what the wires that go to the tachometer are for? Are they essential?

The wire that goes to the ignition is the +12V feed. One of the wires that goes to the tacho will be the signal that tells the tacho how fast the engine's going, I don't know why there's another wire, it's probably a power feed for the tacho, so no they are not essential to making the engine run, only to making the tacho work.

P.S. Does your tacho move as you crank the engine? If it does then this indicates a signal at the coil, if not then no signal.

When testing the spark at the HT bit of the coil, how should i do this. Is the best way to just unplug the HT lead and look for a spark? Or use a volt meter? Sorry if this sounds dumb!

Unplug the lead from the coil to the dizzy at the dizzy end and put a screwdriver in the end. Hold the screwdriver by the plastic handle ( ) close to something metal on the chassis while cranking the engine. The spark should easily be able to jump at least an inch, any less than this and it's too weak. Don't use a voltmeter, you'll fry it.

I don't think my 2 wires go into a surpressor (what does that do anyway).

Check for this, it's a small black box with a heat sink on the back, you can see it at the top of the photo Paul's posted photo attached to his chassis cross member. I'm not too sure about it's function but I think it's there to prevent spikes of voltage travelling from the coil into the other delicate electronics. If you don't have one then it might have fried one or more of your other components.

-fault in the wiring between coil, dizzy and amp

-continuity check with the multimeter

-fault in the power supply to the ignition amp

Unplug the amp and test the wires that go into it. The black one should have +12V, the brown one should go to Earth.

-faulty dizzy (the low tension side)

-not easy, with the three pin types you can put an LED on two of the pins and it will flash, but I think you're is a two pin type, and I'm not sure how to test those.

-faulty ignition amp

- not really possible to test without an oscilloscope. If you've eliminated everything else and still don't get a spark then get a new amp and try it out, it's not unknown for them to fail.

 

Good Luck and chin up

[Guest TheDog]

hi, thanks for all this advice!!

I will take a look at the weekend - and let you know how it goes!!

 

Ta

Chris

[Guest TheDog]

hi, i'm back, having tested everything!

 

It seems the coil is ok (i.e. spark firing), so the problem is definatly on the electric ignition side.

 

After looking at the online manual, and doing some fault diagnostics

http://www.lumenition.com/PMA50ins.pdf

 

Using this i have found that the lead feeding power into the system is feednig the right power, but the two cables that provide the signal out of the distributor to the ingition box, which trips the earth signal to the coil are not working right.

 

Does anyone know if you can buy just the distributor bit of the Lumination optical ignition kit, or would i have to buy the whole thing (i.e. including the little box with the wires going in and out).

 

thanks

chris