My '88 BX 19 GTi has been refusing - point blank - to start all this week.
It's fairly clear that this is an ignition problem as, like the title says, there are "no sparks".
Currently I'm suspecting the ignition coil, it seems fine on the Low Tension side (an ohm or less), but is showing about 6.3 K ohms across the High Tension coil. Is this normal (maybe some suppression resistance in the coil body itself), or is this one duff ?
I don't ever remember replacing an ignition coil before, has anyone else had to do this on a petrol BX (especially an 8v GTi) ?
Lastly, if a new coil is required, are they (as the GSF catalogue suggests) the same for all the BX (8v) GTi's up to '90 ?
Many thanks,
Jim.
BX GTi - no sparks.
Moderator: RichardW
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JamesQB
- Posts: 375
- Joined: 13 Aug 2003, 18:01
- Location: North Wales, United Kingdom
- My Cars: Citroen Xantia 1.8 - I miss this car a lot.
- x 5
An ohm or less is about right for the primary winding (low tension). The Xantia ignition coil has the primary resistance as 0.8 ohms.
The secondary (high tension) has various resistances stated for the different manufacturers, from 7.1Kohms to 14Kohms, so 6.3Kohms sounds adequate to create a high voltage. Thing is, the windings may read okay but how are they actually functioning under electrical load. Sparks may be jumping within the secondary if any of the enamel has cracked or burnt on the copper wire, but under a resistance check, no such thing would show. There's a great deal of difference between a meter reading using millivolts and a few thousand volts going through the coils.
You could check the coil simply enough, just have a lead coming from the HT point of the coil and leave it half a centimeter from a patch of bare metal (earth) on the car chassis, away from battery fumes or petrol (fumes), disconnect the two wires going to the LT side of the coil and take a wire from the battery negative to one LT connector and fix securely, then use a wire coming from the battery positive to hold against the other LT connector briefly. Each time you remove the voltage, you should get a spark leap from the HT wire to the chassis.
I'm not too sure of the BX ignition system, but have you checked that voltage is getting to the contact points and then to the ignition coil? Are sparks being created but not getting anywhere due to a faulty HT lead from coil to distributor or are they not getting anywhere once they arrive at the distributor, perhaps from a faulty rotor arm?
Hope this helps and best of luck,
James
The secondary (high tension) has various resistances stated for the different manufacturers, from 7.1Kohms to 14Kohms, so 6.3Kohms sounds adequate to create a high voltage. Thing is, the windings may read okay but how are they actually functioning under electrical load. Sparks may be jumping within the secondary if any of the enamel has cracked or burnt on the copper wire, but under a resistance check, no such thing would show. There's a great deal of difference between a meter reading using millivolts and a few thousand volts going through the coils.
You could check the coil simply enough, just have a lead coming from the HT point of the coil and leave it half a centimeter from a patch of bare metal (earth) on the car chassis, away from battery fumes or petrol (fumes), disconnect the two wires going to the LT side of the coil and take a wire from the battery negative to one LT connector and fix securely, then use a wire coming from the battery positive to hold against the other LT connector briefly. Each time you remove the voltage, you should get a spark leap from the HT wire to the chassis.
I'm not too sure of the BX ignition system, but have you checked that voltage is getting to the contact points and then to the ignition coil? Are sparks being created but not getting anywhere due to a faulty HT lead from coil to distributor or are they not getting anywhere once they arrive at the distributor, perhaps from a faulty rotor arm?
Hope this helps and best of luck,
James
Thanks James.
Yes - I think I've basically already done what you have suggested: -
* Tried for a spark straight off the coil.
* Checked the coil-distributor (HT) lead resistance.
* Verified that the ignition unit does go short-circuit (very briefly) for the LT coil connection as the engine is turning over. This isn't easy without a 'scope, but it seems to be behaving as expected.
* Verified that there is ~ 12V at the supply side of the coil (LT).
* Proved that the LT connection from the coil to the ignition unit is good.
* Verified that the rotor arm is in fact turning.
I even emulated the Short circuit that the Ignition unit does (it basically grounds one side of the Primary to produce a spark) by manually grounding it - again no spark.
So the evidence so far does seem to suggest that the coil itself is bad. And as you rightly say, the few volts generated by my Fluke may not be enough to show up some breakdown on the Secondary winding - whilst this may well be a very different matter with many KV across it.
Jim.
Yes - I think I've basically already done what you have suggested: -
* Tried for a spark straight off the coil.
* Checked the coil-distributor (HT) lead resistance.
* Verified that the ignition unit does go short-circuit (very briefly) for the LT coil connection as the engine is turning over. This isn't easy without a 'scope, but it seems to be behaving as expected.
* Verified that there is ~ 12V at the supply side of the coil (LT).
* Proved that the LT connection from the coil to the ignition unit is good.
* Verified that the rotor arm is in fact turning.
I even emulated the Short circuit that the Ignition unit does (it basically grounds one side of the Primary to produce a spark) by manually grounding it - again no spark.
So the evidence so far does seem to suggest that the coil itself is bad. And as you rightly say, the few volts generated by my Fluke may not be enough to show up some breakdown on the Secondary winding - whilst this may well be a very different matter with many KV across it.
Jim.
-
philhoward
With a normal dwell of say 40 degrees for ignition, i'd expect so see an average of 5 to 7-ish volts on the switched side of the LT side of the coil; don't expect to see it off a Fluke, though. You'd need an analogue meter to see it (like an AVO).
If it's only going down to deck occasionally, then the ignition amplifier may be playing up by not giving it enough time to discharge the coil into the spark plug.
Quick check; take the coil and send it direct to a spark plug (use one of the plug leads from coil direct to an earthed plug by resting the plug on the engine somewhere). If you get a decent spark when turning the engine over, then something on the HT side of the Dizzy is at fault (rotor arm?). If still no spark, then it's the LT side.
If it's only going down to deck occasionally, then the ignition amplifier may be playing up by not giving it enough time to discharge the coil into the spark plug.
Quick check; take the coil and send it direct to a spark plug (use one of the plug leads from coil direct to an earthed plug by resting the plug on the engine somewhere). If you get a decent spark when turning the engine over, then something on the HT side of the Dizzy is at fault (rotor arm?). If still no spark, then it's the LT side.
The later generation electronic ignition systems don't have dwell time - it's a direct pulse transformation - opposite the old systems with coil energy discharge.
Any voltmeter on the CB side of coil would then read exactly 12V - like the +12V feed side of coil.
There is no need to fiddle using a spark plug for testing the HT of the coil - a good coil with a HT lead should produce a spark of AT LEAST 10-12mm in free air to ground - tested the way Jim tried on the CB side of coil.
If this is not the case - the coil get's over right shoulder for a new one !
Watch out for flying coil [;)]
Any voltmeter on the CB side of coil would then read exactly 12V - like the +12V feed side of coil.
There is no need to fiddle using a spark plug for testing the HT of the coil - a good coil with a HT lead should produce a spark of AT LEAST 10-12mm in free air to ground - tested the way Jim tried on the CB side of coil.
If this is not the case - the coil get's over right shoulder for a new one !
Watch out for flying coil [;)]
Here's an update on this problem:
After some thought and examination of the (in my case) quite inaccurate Haynes Manual wiring diagram, I decided to test the coil again with JUST the battery and a couple of wires - like JamesQB suggested.
My earlier test actually ended up with no real path for the Secondary winding to earth, at the coil itself (although the spark generated should have easily jumped the 1 or 2 mm gap caused when I disconnected the ground here).
This time I made sure that the ground for the coil (both windings) was earthed, and then connected/disconnected 12V to the "+" side of coil (it is marked "+" & "-"). Note that this is not the way it's wired up on the car, hence my previous test.
But I still had the same result - absolutely no spark at all.
So I've been up to my local GSF branch and bought a new coil (just over £20 + VAT).
I've just fitted it and finished the job off - the car now starts and runs just like it did before Monday. And it's MUCH warmer outside than earlier in the week, almost a pleasure to be doing this work now...
My thanks to those who've responded - BTW the fella at GSF said that they do sell quite a few of these coils, as well as the little Ignition Units - which, for my car (early type BX GTi ignition), are roughly the same price
Jim.
After some thought and examination of the (in my case) quite inaccurate Haynes Manual wiring diagram, I decided to test the coil again with JUST the battery and a couple of wires - like JamesQB suggested.
My earlier test actually ended up with no real path for the Secondary winding to earth, at the coil itself (although the spark generated should have easily jumped the 1 or 2 mm gap caused when I disconnected the ground here).
This time I made sure that the ground for the coil (both windings) was earthed, and then connected/disconnected 12V to the "+" side of coil (it is marked "+" & "-"). Note that this is not the way it's wired up on the car, hence my previous test.
But I still had the same result - absolutely no spark at all.
So I've been up to my local GSF branch and bought a new coil (just over £20 + VAT).
I've just fitted it and finished the job off - the car now starts and runs just like it did before Monday. And it's MUCH warmer outside than earlier in the week, almost a pleasure to be doing this work now...
My thanks to those who've responded - BTW the fella at GSF said that they do sell quite a few of these coils, as well as the little Ignition Units - which, for my car (early type BX GTi ignition), are roughly the same price
Jim.