Lost Spark

[Guest mark little]

Thanks for that, plugs are brand new, so they should be ok, so are you saying if I brush a wire over the positive side of the coil there should be a spark at the spark plugs if it is ok? And if I get a 12v coil I don't need the ballast.

 

Cheers Mark

[sj-bradley]

If the coil is a switched ground, then you should take the ground wire and touch it to the battery negative ( it bypasses the dizzy then) and you should get a spark from the plug when you RELEASE the connection. The coil charges when you connect the wire and the rise time is too slow to produce a spark.

 

You won't be able to do this as fast as the engine could, but you only need a few touches to see it work. You will also get a spark from the wire as it will be switching several amps so don't use too thin a wire. 5 amp should do the job.

 

MAKE SURE that you aren't creating a dead short over the battery though and that it is definitely going through the coil. Otherwise the wire will get Very Hot Very Quickly

 

When you release the wire though, the collapse of the magnetic field in the coil produces a large impulse (spark) from the plugs.

 

If the coil has a ballast - it will be a lower voltage coil, probably 6 volts. These date back to when dynamos were in cars and were used to help cold starting as the ballast was bypassed when the starter was engaged allowing the full battery voltage across the coil in order to produce a higher final voltage at the plug (helping it to spark)

 

As the starter draws so much current from a battery, it causes the voltage to drop from around 13.5 volts to possibly as low as 10 volts. This is why the ballast is out of circuit on starting. When the starter has finished and disengaged, the full voltage is now applied to the coil, so the ballast is needed to prevent the coil burning out.

 

With modern electronic control, a 12 volt coil should not suffer the above problems (And they are probably better made now too)

and you should be able to replace the old coil + ballast with a single 12 volt version.

 

Bat +ve ----------- Coil ------- temp wire ------- Bat -ve or chassis

 

That's all you need together with a plug wire from the coil through a plug resting on chassis and you should easily prove the coil and plugs work.

 

Simon.

[Guest mark little]

Cheers Simon, I'll give that a go first thing in the morning

[sj-bradley]

Oh, and even new plugs may not have the right gap so you will need to check and adjust if needed (Not sure of gap size though - Haynes ?)

 

Simon.

[agent_zed]

gap size is 0.78 but i normally just go to 0.8 as its easier.

[Guest mark little]

Coil and plugs work, took the dash out all wires ok, can I test the ballast or electronic points.

Cheers Mark

[sj-bradley]

Unless you know what you're doing with electronic parts - not easily.

 

If you're not careful with electronic parts, you could easily end up with an expensive doorstop.

 

The ballast is likely to be either a coil or large resistor which is designed to drop the battery voltage down so that the coil does not burn out by putting too much volts across it (and as a consequence - too much current through it).

 

With the electronic "points" in place of that temporary wire, you should see the voltage at the coil change while cranking. Best to have an old analogue meter with an old fashioned needle display as you will see the needle twitch. Digital ones will give 12 volts, then 0 or some value in between. Hard to tell what is happening.

 

If you set digital meter on to AC volts (about 20 Volts AC) then you will see the average voltage somewhere between 0 and 12 while cranking. (It will be nonsense while you are not cranking though - it's expecting AC and gets confused with DC)

 

If you have (or know someone) with an oscilloscope though, that is the best way to really see what is happening.

 

Putting a lamp on the coil switched ground will not work as you are simply shorting out the contact points and this will stop the switching effect the coil needs in order to fire the spark.

 

Simon.

[agent_zed]

Finally found my spark :db:

So happy!

 

spent £40 on bits i didn't need but of well.

 

So took the dizzy completely out cleaned it a bit and checked the ohms. Couldn't understand as they were always reading correct specs. Had new coil and new ignition module still no spark so pulled the wiring out and ran an earth lead straight to battery off everything i could see needed to be earthed.

 

Put a bulb in place of the coil and turned the dizzy. and flash flash flash

 

 

put it all back together and fired her up, couple of turns as usual and she was purring again. Was a flippin bad earth from having sat in damp weather for a month or 2.

 

useful tip maybe ... I took the dizzy out and put a cordless drill on the bottom so i could test for spark without having to keep turning the engine over (remember you need to turn the ignition on for power to the dizzy). A 12v bulb between the LT terminals instead of a coil will flash if working correctly as per haynes manual.

 

 

now for an mot

Edited June 7, 2014 by agent_zed

[Guest mark little]

I'm still looking, now have a 12v coil going to fit it this afternoon and see what happens, I'll check all my earths as well.

[Guest peter2b2002]

for those with an efi pinto with electronic dizzy there are 3 wires coming out of the dizzy - ve signal +ve(12v) when the dizzy spins the hall effect sensor switches the signal wire from 0v to 12v that signal goes the the electronic ignition module then coil - spark

I've lost the signal from my dizzy sits about 7 volts all the time

peter2b

[Guest mark little]

I'm still searching for mine, New coil fitted, no different, changed rotor arm, still nothing, power is definitely going into the coil. I'm going to have to get a professional in I think.

[agent_zed]

Hi Mark,

after going through everything step by step you should be able to find your problem.

 

So after going through it myself i would suggest.

 

1. With a multimeter check 12v at coil + when ignition on

2. Test continuity from dizzy cables to first plug connecton. Then reconnect and check continuity from dizzy connection on the sensor to multi plug into the module. (i have the bosch electronic dizzy and the small black motorcraft ign module)

3. Check the ohms between the bottom 2 matching pins (there are 3 pins) are between 1000 to 1500 ohms in the plug that goes to the dizzy.

4. I took the dizzy out as it meant i could spin and check for spark without turning the engine over, I put a jump lead on the body though to ensure it was still earthed).

5. put a bulb (book says 21w but i used a 5w no problems) between the LT connection replacing the coil. when the dizzy turns (and the ignition is on) the light should flash.

6. I wasn't getting anything still so i pulled most of the loom out and connected jump leads to every earth cable i could find and straight to battery to ensure good earth. This was what finally meant i found it was earth fault.

 

Although the module confuses things a little it should really be as simple as ...

 

Dizzy - module - coil - spark

 

I spent £40 on parts i didn't need but it was still cheaper than a garage fault finding and i now know exactly what to check for and how it works so if it happens again i can hopefully fix it again.

 

Good luck

[Guest mark little]

To be perfectly honest with you I just don't understand it at all, rather than fighting on not knowing what I'm doing l would rather get a professional in to go through things and show me for future reference plus I can put it down as work on one of my vans

[sj-bradley]

... That's going to be one Fast Van ...

 

Simon.

[Guest mark little]

It's already chipped to 165bhp, pulls like a train, but it needs to I permanently have a 14' Ifor Williams trailer on the back, usually overloaded.