22 replies to this topic

[tattooguy08]

Very unlikely to be the coil - they are very reliable. Look at points/condenser/rotor arm/dizzy cap/ HT leads pretty much in that order. AFTER - checking there is a voltage getting to the coil - and a lead going from the other terminal on the coil over to the dizzy.

this is partially wrong advice, with some good points added to it. if the ignition has been left on for a considerable lentgh of time then the coil can become damaged and stop working.

if you have no spark from your coil, then you need to check the low tension side of your ignition system.

just a quick reminder of how the ignition system works, the low tension side is built up of the coil, points, condensor, the points create an open circuit in the system creating the HT spark.
the HT side is made up of the coil output, king lead to the dizzy, rotor arm in the dizzy, spark plug leads, and then of course the spark plugs.

when the points inside the dizzy are closed the circuit is closed, a charge is then built up in the coil, and as soon as the points open the spark will travel from the coil along the king lead, into and then through the dizzy to the spark plugs, if the points do not open or stay open, then the circuit will not create the spark in the coil.

a simple test which i teach is to get a test lamp, ( a bulb with 2 wires on it) connect one end to a good earth point on the engine.
dosconnect the lead going into the dizzy.
turn the ignition on, and then see if you have power at the + side of the coil. if you don't then you have an open circuit in the wire from the ignition switch to the coil.
if the light comes on, then check the output - side of the coil. if the light fails to come on then the coil needs to be replaced.
then check the wire from the coil the the dizzy, where you disconnected it. again if the light fails to come on then you have an open circuit in that wire, change it.
if you have power at this lead then the fault is in the dizzy.
check the points are opening, check that the points have not been fitted wrong,(the wires going onto the points could be touching the base plate, this will create an earth before it should)

hope this helps

if the light comes on at everything on the coil apart from the connection to the dizzy... Does that mean the coil is foobared?

[dklawson]

In his test above Cowboy is using the light to show where there is and is not electricity.  Repeating the test steps here...

Disconnect the low-tension factory wire between the dizzy and coil (-) terminal. This is a "must do" step.

Switch on the ignition.

1) Connect your test lamp between coil (+) and earth.  Note if the lamp is on or off.

2) Move your test lamp connections so they are between coil (-) and earth.  Note if the lamp is on or off.

 

With the factory wire disconnected between coil (-) and the dizzy, the light should be ON in both tests above.

If the lamp is OFF in the first test, voltage from the ignition switch is not reaching the coil.

If the lamp is ON in the first test and OFF in the second test, voltage is not passing through the coil... which indicates a failure of its primary windings (repair is by replacement).  

 

That's not a direct answer to your question but I want to stress that for Cowboy's tests you need to disconnect the low-tension factory wire between coil (-) and the distributor.  With that wire in place you cannot use this test.

[ChopperHarris]

80s Mini, positive earth... WHAT???!!!!!!!

[dklawson]

80s Mini, positive earth... WHAT???!!!!!!!

 

 

I don't believe anywhere above anyone mentioned positive earth.  I DID say to use the test lamp between coil (+) and earth.  That's not the same thing.

[Norbie8888]

I have the same problem, and using the bulb test I get a light on the + AND - on the coil...   so wiring to the coil is ok, as is the Coil... 

 

the leads are also new...   but I'm not getting a spark from the KING HT lead that goes into the dizzy... (I've kept it plugged into the coil, then very close to a good earth and tried to turn it over.. no spark.

 

whats next? 

 

thanks guys x

[KernowCooper]

What year is yours ?

[dklawson]

And what has been done to/with the engine since it last ran?

[Jamesminibutler]

Hi I have 1275 engine with pre engaged starter motor is also as a solenoid on inside of arch it started up today for the first time made a popping noise then lost all power I have ignition light but nothing when turning the key any help please
Thanks James