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Ignition woes
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kevin2306



Joined: 01 Jul 2013
Posts: 1359
Location: nr Llangollen, north wales

PostPosted: Fri May 30, 2014 7:40 pm    Post subject: Ignition woes Reply with quote

had a few problems with the singer last sunday.
decided to change the coil, dizzy cap and rotor arm (easy huh)

Not a peep! no spark (slight one when switching the ignition off)

changed the coil, cap and rotor back to the old one..nothing still.

so, with the ignition switched on (some sort of electronic ignition fitted) I have about 11v across the coil..should that be a full 12v?
Checked everything I can think of, changed the ignition leads for another set..nothing.

only thing im not sure about is this little blighter that is next to the coil, linked to the - terminal..what is it and will this kill the ignition if its defunct..how important is the earthing to the body of it (bolted using the same bolt as the coil bracket)



Help!

Kev
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47Jag



Joined: 26 Jun 2008
Posts: 1480
Location: Bothwell, Scotland

PostPosted: Fri May 30, 2014 9:11 pm    Post subject: Reply with quote

Kevin,

That's a condenser that has been fitted for radio noise suppression. You can take it off if you want. It shouldn't affect anything. The thing about transistor ignition is that the transistor has to be turned on by whatever the trigger sensor is. Apart from using the existing point some systems use photocells, others use a Hall Effect transistor. (1) Monitor the coil with your voltmeter when you crank the engine over. You should see a ON/OFF pattern. (2) Take the main coil wire from the distributor and hold it about 3/8" from the block and while the engine is cranking, you should see a nice blue spark leap between the wire and the block. If you get that, the coil and the electronics are OK and the problem could be in the distributor cap or rotor arm. (3) Take the distributor cap off and hold the coil wire above the centre of the rotor and crank the engine again. If the spark leaps to the rotor then the rotor is leaking to earth. Replace it. If the rotor tests OK look at the cap for signs of tracking. These look like cracks. Report back after trying these.

Art

Art
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kevin2306



Joined: 01 Jul 2013
Posts: 1359
Location: nr Llangollen, north wales

PostPosted: Fri May 30, 2014 9:29 pm    Post subject: Reply with quote

Weirdly, I went back in the garage just to take advantage of it being dark and check for arcing out.
She fired up without an issue!
So, tomorrow I will remake the connectors to the coil (soldered joints) and pop to get a new dizzy cap-coil ht lead.
May be time for a new electronic ignition system? do they have a life span?


Hate cars me

Kev Very Happy
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ukdave2002



Joined: 23 Nov 2007
Posts: 4100
Location: South Cheshire

PostPosted: Fri May 30, 2014 10:44 pm    Post subject: Reply with quote

Kev

Aftermarket electronic ignition systems are pretty reliable, they are all based on the simple "transistor assist" systems that were fitted by vehicle manufacturers since the 60's, so quite well proven! That said if the vehicle has a dynamo, the electrical noise from electromechanical regulation can cause problems.

If they have an optical sensor, this can get dirty and give spurious results, heat and cold can induce intermittent faults; if you go into any electronic repair workshop, you will find a hair drier and aerosol freezer sprays used to hunt down heat related faults, they can be as simple as a dry joint that fails when it heats up or a component that is failing with a temperature change.

Generally electronic ignitions either work or are dead! You don't mention which system it is? Does it retain the points? If so has the original condenser been removed?

Cheers

Dave
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kevin2306



Joined: 01 Jul 2013
Posts: 1359
Location: nr Llangollen, north wales

PostPosted: Fri May 30, 2014 10:56 pm    Post subject: Reply with quote

Unsure of make dave, it doesnt retain the points.
When checking things earlier (after having a break) i could hear something clicking in the distributor as i flicked the ignition switch, that led to seeing a spark at the plug leads and then the car firing up. Almost as if the system needed to recharge after being discharged. See how i get on tomorrow.

Weired

Kev
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ka



Joined: 03 Dec 2007
Posts: 600
Location: Orkney.

PostPosted: Sat May 31, 2014 6:26 am    Post subject: Reply with quote

Call me old fashioned if you like, but I like points; they rarely fail completely, just fade away, so at least electrical issues can be checked and if it stops in the middle of nowhere, you do stand half a chance of sorting it. I add an electronic ignition assist, optimistically hoping for the best of both worlds!
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Phil - Nottingham



Joined: 01 Jan 2008
Posts: 1252
Location: Nottingham

PostPosted: Sat May 31, 2014 6:52 am    Post subject: Reply with quote

I agree with KA and after having 2 units fail leaving me stranded I have reverted to points which if properly set up and maintained are far more reliable and easy to fix if any parts fail
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ukdave2002



Joined: 23 Nov 2007
Posts: 4100
Location: South Cheshire

PostPosted: Sat May 31, 2014 9:08 am    Post subject: Reply with quote

ka wrote:
Call me old fashioned if you like, but I like points; they rarely fail completely, just fade away, so at least electrical issues can be checked and if it stops in the middle of nowhere, you do stand half a chance of sorting it. I add an electronic ignition assist, optimistically hoping for the best of both worlds!


I agree with fitting an electronic ignition that maintains the points, for 2 reasons:

1) It's possible to wire in such a way that if the electronics fail, you can revert to conventional ignition at the flick of a switch.

2) The optical and magnetic triggers that replace points, add no benefit over properly set up points. The benefit of all the aftermarket electronic ignition systems is that they switch the current to the coil far more efficiently than points ever can, resulting in more energy being available at the sharp end of the ignition system. The £10 kit that Maplin used to sell, was as effective as other aftermarket systems costing many times more.

I stress again that none of the after market ignition system that I have come across are designed to work with dynamo's ; if you do fit one to a vehicle with a dynamo add a snubber or Zener diode across the supply (cost about £1.50!) to protect the unit.

Dave


Last edited by ukdave2002 on Sat May 31, 2014 9:18 am; edited 1 time in total
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kevin2306



Joined: 01 Jul 2013
Posts: 1359
Location: nr Llangollen, north wales

PostPosted: Sat May 31, 2014 9:15 am    Post subject: Reply with quote

there is a diode fitted dave, do they break down? assuming they do, where can I get a replacement from?

so many questions huh

kev
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ukdave2002



Joined: 23 Nov 2007
Posts: 4100
Location: South Cheshire

PostPosted: Sat May 31, 2014 9:24 am    Post subject: Reply with quote

kevin2306 wrote:
there is a diode fitted dave, do they break down? assuming they do, where can I get a replacement from?

so many questions huh

kev


Fitted across the supply?

Like anything they can fail, Maplin will have them, here is a better description of them; http://en.wikipedia.org/wiki/Transient-voltage-suppression_diode

..they cost pence!

Dave
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kevin2306



Joined: 01 Jul 2013
Posts: 1359
Location: nr Llangollen, north wales

PostPosted: Sat May 31, 2014 10:11 am    Post subject: Reply with quote

If its the part on the ignition that im thinking about, it is between a wire from the distributor to coil, and looks like a small heat sink type gadget?
spade connector each side and bolted to the car body.
does this sound correct?

Kev
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D4B



Joined: 28 Dec 2010
Posts: 2083
Location: Hampshire UK

PostPosted: Sat May 31, 2014 10:34 am    Post subject: Reply with quote

kevin2306 wrote:
If its the part on the ignition that im thinking about, it is between a wire from the distributor to coil, and looks like a small heat sink type gadget?
spade connector each side and bolted to the car body.
does this sound correct?

Kev


Isn't that what they called a ballast resistor?
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kevin2306



Joined: 01 Jul 2013
Posts: 1359
Location: nr Llangollen, north wales

PostPosted: Sat May 31, 2014 11:17 am    Post subject: Reply with quote

This is the item in question



made by lucas if that helps

so, into garage early this morning. car is dead once again, so definitely something breaking down id say.
I have 12v to the coil but this drops to 10v when cranking!
if the ignition is left on, the coil warms up as expected but the lucas item above also heats up.
Blood annoying as I am totally out of my depth with ignition systems.

kev
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kevin2306



Joined: 01 Jul 2013
Posts: 1359
Location: nr Llangollen, north wales

PostPosted: Sat May 31, 2014 11:30 am    Post subject: Reply with quote

interweb is a fantastic thing eh

the item in question is a ballast resistor

http://www.ebay.co.uk/itm/Lucas-Drive-Resistor-Ballast-for-MG-Triumph-54427556-/281207324207?pt=Motors_Car_Truck_Parts_Accessories&hash=item4179433e2f

so, next question is what does it do and will this be a likely cause for my woes?
do i replace it or do i get a coil with built in ballast resistor?

kev
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D4B



Joined: 28 Dec 2010
Posts: 2083
Location: Hampshire UK

PostPosted: Sat May 31, 2014 12:58 pm    Post subject: Reply with quote

Took this from Wikipedia:

Fixed resistors

For simple, low-powered loads such as a neon lamp or an LED, a fixed resistor is commonly used. Because the resistance of the ballast resistor is large it determines the current in the circuit, even in the face of negative resistance introduced by the neon lamp

The term also referred to a (now obsolete) automobile engine component that lowered the supply voltage to the ignition system after the engine had been started. Because cranking the engine causes a very heavy load on the battery, the system voltage can drop quite low during cranking. To allow the engine to start, the ignition system was designed to operate on this lower voltage. But once cranking is finished, the normal operating voltage would overload the ignition system. To avoid this problem, a ballast resistor was inserted in series with the ignition system. Occasionally, this ballast resistor would fail and the classic symptom of this failure was that the engine ran while being cranked (while the resistor was bypassed) but stalled immediately when cranking ceased (and the resistor was re-connected in the circuit).

Modern electronic ignition systems (those used since the 1980s or late '70s) do not require a ballast resistor as they are flexible enough to operate on the lower cranking voltage or the normal operating voltage.

Another common use of a ballast resistor in the automotive industry, is adjusting the ventilation fan speed. The ballast is a fixed resistor with usually two center taps, and the fan speed selector switch is used to bypass portions of the ballast - all of them for full speed, and none for the low speed setting. A very common failure occurs when the fan is being constantly run at the next-to-full speed setting (usually 3 out of 4). This will cause a very short piece of resistor coil to be operated with a relatively high current (up to 10 A), eventually burning it out. This will render the fan unable to run at the reduced speed settings.

In some consumer electronic equipment, notably in television sets in the era of valves (vacuum tubes), but also in some low-cost record players, the vacuum tube heaters were connected in series. Since the voltage drop across all the filaments in series was usually less than the full mains voltage, it was necessary to get rid of the excess voltage. A ballast resistor was often used for this purpose, as it was cheap and worked with both AC and DC.
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