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Author Topic: Is coil failure the answer?  (Read 16109 times)
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Thotos
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« Reply #20 on: October 28, 2013, 08:25:31 PM »

I got a multimeter and checked what was happening at the coil:

The voltage measured at the outer poles (the primary winding) = 6.2 volts


Do you mean you measured the voltage across the two poles of the coil? If so, that's wrong. You need to measure the voltage at the +ve terminal of the coil. That's the one that has the wire going onto the ballast resistor. And to be on the safe side and make sure you have a good earth, put the negative probe of your voltmeter on the battery -ve pole and the positive probe of the multimeter on the +ve terminal of the coil. If, as I suspect, you get 7 volts, then bypass the ballast resistor and the car will most probably start. When (and I'm not saying 'if'  Wink ) the car starts, measure the voltage again on the coil +ve terminal with the engine running and report back please.

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lbcoupe76
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« Reply #21 on: October 28, 2013, 08:53:31 PM »

Heat is generated by current, the lower the voltage the higher the current, A failing resistor will lower the voltage as the resistance increase's leading to excess heat across the resistor.
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speedyK
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« Reply #22 on: October 28, 2013, 09:23:48 PM »

put the negative probe of your voltmeter on the battery -ve pole and the positive probe of the multimeter on the +ve terminal of the coil.
Thanks, I was doing it wrong. Measuring as you say, it gives 7.64 volts.

bypass the ballast resistor and the car will most probably start. When (and I'm not saying 'if'  Wink ) the car starts, measure the voltage again on the coil +ve terminal with the engine running and report back please.
With the resistor bypassed, it still won't start. No spark at the end of the coil to distributor lead when held a couple of mm from the engine.
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Thotos
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« Reply #23 on: October 28, 2013, 11:39:59 PM »


With the resistor bypassed, it still won't start. No spark at the end of the coil to distributor lead when held a couple of mm from the engine.


OK, next things to check are:

1. Voltage at the coil +ve terminal with ballast resistor bypassed. Normally this would be 12V but as you only had 7.6V before I'd expect at least 9Volts. That should be enough for the coil. If you have 9 volts or more, make sure you still have them while cranking the engine.

2. Check the earth strap on the engine. Use the meter in resistance measurement between the engine and battery -ve pole. It should be 0 ohms. Assuming that it is, measure it again while cranking the engine. It should stay at 0 ohms.

3. Test the HT lead from the coil to the distributor. Best way to test is swap it with a known to be good one.
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speedyK
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« Reply #24 on: November 01, 2013, 03:54:05 PM »

Thanks for the further tips  Smiley


I must admit that I'm getting heartily sick of this now   Undecided

Been away for a couple of days. Left the new battery on the battery conditioner.

Did the tests as suggested:

With ballast resistor bypassed
Voltage at +ve terminal of coil (other lead to battery -ve pole) = 11.5 V (Don't ask me why!)
When cranking: 10.5 V

With ballast resistor in place (normal)
7.5 V

Resistance check
-ve lead on -ve pole of battery, +ve lead on engine
with ignition OFF = ca. 2.4 Ohms
with ignition ON = ca. 300 Ohms
cranking engine = ca. 600 Ohms

 Huh?






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Per
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« Reply #25 on: November 01, 2013, 06:41:37 PM »

The voltages are normal. The ign off resistance is normalish, what resistance do you get directly across the voltmeter probes, i.e. touching one with the other?

Resistance with a live circuit cannot be measured with an ohmmeter (but you can wreck the ohmmeter).

Check the voltage between negative pole on the coil and ground with ignition on. You should get either close to 11.5 or close to zero. Try cranking for just long enough to turn the engine a wee bit several times. You should get either of those measurements.

BTW check that all spade connectors are tight. If not pull off and give a gentle squeeze with a pair of pliers.
« Last Edit: November 01, 2013, 06:45:03 PM by Per » Logged
speedyK
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« Reply #26 on: November 02, 2013, 05:24:02 PM »

Thanks for keeping at it  Smiley

what resistance do you get directly across the voltmeter probes, i.e. touching one with the other?
About 0.3 Ohms

Check the voltage between negative pole on the coil and ground with ignition on. You should get either close to 11.5 or close to zero.
I get about 0.02 V


Check the voltage between negative pole on the coil and ground with ignition on. You should get either close to 11.5 or close to zero.
I'm getting 0.02 V

check that all spade connectors are tight. If not pull off and give a gentle squeeze with a pair of pliers.
All tight...



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Per
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« Reply #27 on: November 02, 2013, 10:18:06 PM »

All good news. Except for the condition of the coil that is. But one last check: Measure resistance beween coil housing and engine which should be zero volts. If OK you should have a big fat spark if connecting a plug directly to the coil high voltage lead and just resting the plug on the engine. With the electronic ignition there is normally either a good spark or none at all as far as the electronics are concerned.
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speedyK
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« Reply #28 on: November 02, 2013, 10:43:15 PM »

All good news. Except for the condition of the coil that is.
So, you reckon it is the coil - not the ballast resistor?

one last check: Measure resistance beween coil housing and engine which should be zero volts.
Not getting any reading, so presume that's a zero.

If OK you should have a big fat spark if connecting a plug directly to the coil high voltage lead and just resting the plug on the engine. With the electronic ignition there is normally either a good spark or none at all as far as the electronics are concerned.
I had already tried this last week, holding a plug against the end of the HT lead (connected by using insulated pliers to clamp them together, as the HT lead does not have the part to fit on the plug) and holding the tread of the plug against the engine. Not sure that the connection made between the coil lead and the plug is adequate - but I couldn't see any spark...
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Per
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« Reply #29 on: November 02, 2013, 11:11:14 PM »

Reading between coil housing and engine should be a decisive zero. Most of the coil is painted and in theory high voltage should jump that resistance easily. However if it has been sitting for a while the corrosion between coil housing and engine could have increased significantly. I would loosen the clamp, slide out the coil and sand coil body and inside of clamp lightly. Ditto clamp and engine. Then simply short out the resistor. If still no spark time to try another coil that is known to be good.
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speedyK
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« Reply #30 on: November 03, 2013, 12:34:06 PM »

I can't see that that corrosion could be an issue, as the car worked fine before and was in a dry garage.

Similarly, I can see no reason why the HT lead from the coil could suddenly fail. As a lay person, I could understand a coil suddenly failing more easily.

I don't have any option to borrow a coil, so I suppose I will have to buy a new one to find out.

I would have preferred to be sure that there were no other feasible reasons for a sudden loss of function (the electric control box for the ignition was my other suspect). It would be annoying to pay for a new coil and find no change in the situation.

New questions:
Can anyone recommend a reliable UK supplier for a new coil for a 1981 Beta Spider 2000?
 Is the ballast resistor supplied with the coil?
If I'm ordering anyway and will have to pay postage to Switzerland, I suppose a new coil-dizzie lead and distributor cap plus rotor arm is a sensible idea too while I'm at it.
Any UK supplier stock these items as well as the coil?
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peteracs
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« Reply #31 on: November 03, 2013, 03:53:27 PM »

Hi

Given the coil is not that specific to your installation, do you know anyone who has a spare from another car just to prove the point?

At the end of the day all they do is provide enough HT to cause a spark, so any coil should give you at least proof it is the coil?

I agree, expensive if not sourcing from locally.

Peter
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Thotos
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« Reply #32 on: November 04, 2013, 01:57:41 AM »

Sorry, I haven't been ignoring you but I've been away for a few days with no Internet access.

I would say with some certainty that the ballast resistor is not faulty. You get the right sort of voltage with the ballast connected and you've bypassed the ballast to eliminate the possibility of it being the fault.


Resistance check
-ve lead on -ve pole of battery, +ve lead on engine
with ignition OFF = ca. 2.4 Ohms
with ignition ON = ca. 300 Ohms
cranking engine = ca. 600 Ohms


That's not right!  Undecided  You should have zero ohms between the battery negative terminal and the engine at all times. Check the battery negative lead where it bolts to the chassis and make sure the connection is clean and tight. Also check the engine earth strap. I'm not sure where it's located on your car but there must be an earth strap from the engine to the chassis somewhere and it should have clean and tight connections both ends. Per's suggestion of measuring the resistance between the coil body and battery negative terminal is a good one and along the same lines. If the resistance measured there is not zero then you have a bad earth connection either where the battery negative terminal connects to the chassis (which would explain the strange resistance readings between the battery and engine) or where the coil bolts to the chassis. As a test you can connect a jump-lead between the battery negative terminal and the coil's mounting point on the chassis. To test for a spark at the coil, use a spark plug at the end of a spark-plug lead and plug the spark plug lead into the coil. You may have to move the boot back to be able to plug the lead into the coil. But check again your negative connections from battery to chassis, from chassis to engine and from coil body to chassis. You should get zero ohms at all times between any of those points.

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Theo Kyriacou
speedyK
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« Reply #33 on: November 14, 2013, 11:41:26 PM »

Tried it again and got 0 ohms. I think I may have accidentally tried the positive pole of the battery last time  Roll Eyes

I have ordered a new coil, as I can't find any other explanation.
I hope it arrives soon, as I want to get the Lancia out of my garage and into its usual underground parking space before winter gets hold. We've already had sub-zero temperatures here.
The Lancia is on summer tyres (I do have a set of steel rims with ancient winter tyres that are not fit to drive - I only use them e.g. to be able to move the car when the alloys are away getting new rubber).




My winter use cars are all on their winter tyres now and my Smart roadster normally has that space.
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speedyK
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« Reply #34 on: December 14, 2013, 04:46:30 PM »

So, after the coil supplier who promised dispatch within three working days finally got the coil to me after nearly 4 weeks, I fitted it.


Not one jot different.

If I disconnect the HT lead from the coil to the distributor and crank the engine, there is on spark whatsoever - until the ignition is turned off and THAT causes the emission of a brief spark.

What the hell is wrong?
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speedyK
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« Reply #35 on: December 14, 2013, 09:17:59 PM »

I'm now wondering if it is the Bosch electronic control unit.

Anyone know if these available anywhere?
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Per
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« Reply #36 on: December 14, 2013, 11:02:13 PM »

What type of trigger does it use for the ignition? If it uses a circular magnet on the distributor shaft triggering a hall element I have experienced the magnet cracking, seemingly when cooling down because it would not start after stopping and attempting restart the nexy day. If it uses a crank sensor (cannot remember when the first instances came) those are a weak spot in many applications. The system would charge the coil ans switching off the coil would fire once as you described.
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speedyK
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« Reply #37 on: December 15, 2013, 11:10:47 AM »

Ah, interesting.
I'll have another look at it.
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Thotos
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« Reply #38 on: December 15, 2013, 10:24:07 PM »

There's no crank sensors on Betas. The problem must be either with the pickup sensor in the distributor or the electronic control unit or, of course, the associated wiring.
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Theo Kyriacou
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« Reply #39 on: December 16, 2013, 09:50:52 AM »

There's no crank sensors on Betas. 
Precising your answer in late i.e. versions with digiplex ignition there is a crank and a cam sensor.
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