No spark from coil.

[maraman45]

hi. i am unable to get a spark from my coil. I have bought a new one. when i connect battery the dash comes live. Obviously a short somewhere. How should the coil be wired. I havebought anew one with neg and pos connects. The old one had sw and cb on it. Any ideas?..

[MarkyB]

If the car is negative earth then connect the points to the negative terminal.

[Alec]

Hello Maraman45,

have a look at your fuse block to see if one fuse has been replaced wrongly, between the two sets of clips rather than in it's own clip.

Alec

[bmcecosse]

It's NEVER the coil!!!!!!! Refit the old one. Ignition circuit is not fused - the spark comes when the coil is earthed by the points. Look to the points/condenser to find out what's wrong.........

[beero]

Welcome to the forum. Have you proved the coil to be faulty or are you just guessing or hopeing?

[maraman45]

How do I tell if car is negative or positive earth?? I'm assuming sw means switch, but what about cb?? I thought the coil would spark if you held the lead to the block and turned the car over. What wires should be connected to the coil?? Thanks for your help. Much appreciated

[Alec]

Hello Maraman45,

yes, you should get a spark if the ignition is on and the coil is connected. CB is the connection to the coil (white\black wire), and the SW should have 12 volts on it with the ignition on. Look at your battery , there is a + (positive) and a - (negative) near the terminals, just look to see what terminal is connected to the car body.

Alec

[bmcecosse]

It will only spark if the points/condenser are doing their job........... I say again - it's NEVER the coil......

[Sandun]

dont wory - the wire that come out from distibutor is (-)/CB- 1st on your car, using key then check the coil + using multimeter it must be 12 v come, then off key - open distibutor cup check(-) wire ok, use multimeter , look at points if it open not volts come(coil off) if it close coil on-the work of the contact point as a swich ,it on and off coil, using (-)wire of coil , and check ur hitention wire that come coil from distibutor -and check ur battary voltege fine

[bmcecosse]

Your English is certainly improving Sandun!

[beero]

The second to last paragraph here will help with the SW CB problem

http://mgaguru.com/mgtech/ignition/ig109.htm

If you have power to your coil you can test/reproduce what the points do by removing the wire going to the points and just touch an earth wire to that coil terminal. When you release the earth wire the coil should spark.

[bmcecosse]

Or just put a meter on it - should read 3.2 ohms.

[maraman45]

Thanks for all your help. My other query is where do the wires go to from the ignition switch. There are 2 connections on back and it is a pull start set up. Cheers

[Sandun]

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[bmcecosse]

White wires - one to fuse box and other to fuel pump and coil...... See Barry's excellent diagram at the head of the Electrical section.