Electrical no spark

[Abc12]

HI all from a new member, got a problem with my moggy no spark from king lead on the coil or plugs ,or the points . The coil is new and tried another two new ones as well.I have 12 volts to the coil showing on multimeter.i only get a very faint spark if i short the king lead out. Also tried a new electronic dizzy with no luck . Not tried points or condenser yet. Been working trying to sort for the last 3 days. It did run fine changed the head gasket now this.

Also new battery coming tomorrow just in case the old one is weak.

Surely there cant be much wrong but any help would be very appreciated.

Andy

[oliver90owner]

If you short out the king lead, you will not get a spark! Please explain, more precisely, what you are trying to do.

Testing for a spark at the king lead is to hold the lead 6-10mm from a good earthing point and switch the coil supply, at which point a spark should be induced. A weak spark usually indicates a failed condenser if the coil is good. Try the test without the pigtail lead in circuit.

The coil should draw 3-4 amps when connected to power. If it doesn’t, you likely have a poor connection to the coil (as you have presumably changed to good coils). A simple voltage check, at a terminal, is not always a definitive test for a circuit.

[myoldjalopy]

If it was 'running fine' before changing the head gasket, could you have disturbed any of the ignition system wiring when changing the gasket? Unlikely to be the coil itself if you have tried three new ones. It is worth checking the condition of the points and the gap(easy to do) but, otherwise, what 'oliver90' has said.

[Abc12]

Firstly thank you for the reply ,i'm pulling my hair out try to get the old girl to go. On the Moggy forum there was a test to check coil , which if i remember right said remove the king lead from the dizzy cap a hold close to the engine block, then attach a lead with a good earth point on the car and the other end to the negative side of the coil. Then when you remove the earth lead from the negative side of the coil you should see a good spark from the king lead from the coil to the engine block.

I know that your need a good set of points and condenser and the small earth wire in the dizzy, but shorting the coils as above should work even if the points and the other parts need replacing in the dizzy, wouldn't it . i know i've disturbed the timing as well would that also play a part in the problem.

I also have fitted a new electronic dizzy to rule out points issues but couldn't get a spark with that.Who had the car prior to me had fitted a alternator badly and the wiring in the rest of the car is not very good with the connection all over the place but managed to sort out. check the wiring to the ignition side and all looks ok,

PS what is a pigtail lead
Also all coils are new along with the electronic distributor.
Cheers
Andy

[Bill_qaz]

When you did your temp earth wire make and break wire to test the coil did you remove the existing wire to the distributor?

[myoldjalopy]

The 'pigtail' lead is the one that takes the current from the coil connection to the dizzy to the points, also known as the low tension lead.
If you have disturbed the timing that should not stop you getting a spark - it will just occur at the wrong time and thus the engine will not fire, or if it does, it will not run well.

[Abc12]

cheers thanks for that, when i did the test it said remove negative wire from the coil to do the test. Also the post about the points that's what i thought should still spark but just run rough. Also if i open the points manually no spark, In a nutshell no spark anywhere that's what i can't work out. There is 12 volts going to the coil. Going to try again when new battery turns up today.

Andy

[geoberni]

Dare I ask if you have a Morris/BL Workshop Manual?
There's a good process to work through for fault finding the Ign system....
.
.
.
Edited my spelling of 'Dare', as Eric Morecambe might say, I had all the right letters, just not in the right order...

[Bill_qaz]

[Abc12]

I ve got a haynes manual been through the tests in that but no luck. Just fitted the electronic dizzy no spark but battery fairly low.

Andy

[geoberni]

I ve got a haynes manual been through the tests in that but no luck. Just fitted the electronic dizzy no spark but battery fairly low.

Andy

I can't vouch for the Haynes Manual, I've never been a fan of their books. They may have copied the Morris one, they might not.

[simmitc]

For fault finding, remove the electronic dizzy and stick with points. (a) it's easier to see what's happening and (b) easier to test each stage. Also, some electronic units will not trigger unless the engine is spinning quite fast, whereas points will open and close at any speed.

Is the car original +ve earth or converted to -ve? Important to get the coil connections correct - it will work the wrong way round, but is better the correct way.

Double check everything from the beginning.
Disconnect both low tension wires form the coil. Using a multimeter, check the resistance between the two LT terminal on the coil. You should see around 3 ohm.
Now measure resistance between the CB or -ve LT terminal and the central HT connection. Expect >5 Kilo Ohm.
With both readings in the correct range, the coil is OK.

White wire to coil - check for 12 volts.
Connect a 21w bulb (such as an indicator bulb) with one terminal to the white wire and one to earth. Does the bulb illuminate at full brightness? If yes, then there should be sufficient current (amps) to get at least some spark.

Connect the white wire to the correct terminal on the coil (depending on +ve or -ve earth).

Fit one end of an HT lead to the coil and place the other end about 3/8 inch or 10mm from a good earth point such as the block. For this test, a plain old-fashioned copper HT lead with an easily exposed end is best rather than anything fancy like suppressed or carbon.

Take a piece of ordinary low tension wire and connect one end to the other LT terminal on the coil, then alternately touch and remove the other end to a good earth point. Expect a spark at the free end of the LT wire as you touch and remove to earth, but there should also be good spark from the HT lead to earth.

Once the above is completed and working, then we can move onto the dizzy side of things.

[Abc12]

Hi thanks for the the info the car is negative earth, will do the coil test tomorrow but have already checked it a couple of days ago and was ok. As for the other test regarding the HT lead again i will do tomorrow ,again ive already done this test but how you have explained it i don't think i did it correctly, the HT side on the block was correct but i didn't connect a wire to the LT terminal on the coil, then the other end touch and remove to a good earth.

Will do that test tomorrow now you've sent the correct way to do it, might of been me not understanding when reading it a couple of days ago . Hopefully will get a spark from the coil tomorrow.

Waiting for some bits to come to rebuild the points dizzy as a wire has come adrift from the LT terminal . As for the electronic dizzy would a weak battery cause any problems ? i've got a new battery ordered as well. WIll let you know regarding the tests Fingers crossed.

[myoldjalopy]

Well, 'simmitc' has already pointed out that 'some electronic units will not trigger unless the engine is spinning quite fast.'
The state of charge of a battery is easily tested - if the starter motor will consistently spin the engine briskly without signs of flagging, there can be little wrong with the battery. Of course, it must be fully charged.

[simmitc]

Guidance on connections: For a -ve earth car, the white lead from the ignition should go to the +ve or IGN terminal on the coil. The white/black lead to the dizzy or, initially the test to earth lead, goes to the -ve or CB terminal.

[Abc12]

Afternoon just done the two tests as suggested on the 3 coils 1 coil is dead which was new, the other 2 coils show as follows 2.9 and 3.2 ohms and 8.23 and 8.9 kilo ohms. then tried the test reference to get a spark from the king lead by putting king lead near block and earthing out the negative lead from the coil to a good earth ,good spark from this lead but nothing from king lead.No spark from the king lead. Battery fully charge .The only thing maybe the battery is no good ,new one not arrived yet.

Multimeter showing 12.4 volts across battery terminals
Any idea why not getting a spark.

[Bill_qaz]

Try one of your other plug leads and repeat the test your king lead maybe faulty.
Have you done a continuity test on the lead with your meter?

[Abc12]

cheers will check in the morning

Andy

[Abc12]

Hi all took the advice given went back to points and good news got a spark on the plugs.Wonder if the electronic distributor was faulty . Thanks for all the help


Andy

[les]

Good old fashion points ! Why make a road going Minor complicated ?