Series 2 - won’t spark positive earth

Funonthefarm · Apr 7, 2024

Hi all, spent all day messing with this and still no joy!

Just putting back together my series 2 - positive earth: before I took it to pieces, the engineer fired and ran well.

Now started to reassembly and it won’t fire or spark. The wiring was a dogs dinner, so have run a 12v jumper to the coil, but can’t get a spark at the plug.

I do get a spark at the lead from the coil / centre lead to the distributor.

Am I right in thinking that I run the 12v negative to the negative on the coil and the wire from the lt on the cap to the positive side of the coil?

Any help is welcome!!!

tottot · Apr 7, 2024

With positive earth the feed from switch goes to negative on the coil and the coil positive goes to the dizzy.

Funonthefarm · Apr 7, 2024

tottot said:
With positive earth the feed from switch goes to negative on the coil and the coil positive goes to the dizzy.

Thanks for the reply, I’ve tried every feasible combination, but can’t seem to get a spark at the plug. It was all running before I stripped it down. It was a new coil, dizzy cap and arm before and new ht leads too…

The only thing I’ve done was free of the vacuum advance adjuster…. Could that be causing a problem?

Also could I have blown something having tried them the other way round like the condenser etc….

tottot · Apr 7, 2024

Condenser damage possible.

Funonthefarm · Apr 7, 2024

tottot said:
Condenser damage possible.

Is there a east way to check?

Rangieman123 · Apr 7, 2024

Ill assume that it's unknown if you have a pos or neg earth coil.
To isolate the fault I would suggest the following:
Put a plug lead into the coil HT connector with a properly earthed spark plug at the other end.
Turn the engine by hand until your points are fully open, as this prevents getting the coil hot...
Turn on the ignition. Using a small screwdriver, bridge the arm on the points to the points body while keeping an eye on the spark plug. Release the screwdriver slowly.
If you get a weak spark/nothing at the plug and also weak spark/nothing at the end of the screw driver your coil is wired the wrong way round.
If you get a normal spark at the plug and a big audible spark at the points, your condenser is toast.

Rangieman123 · Apr 7, 2024

There's a very thin wire in the distributor that earths the points baseplate to the distributor body. This can break, resulting is nothing happening.
At this stage I suggest establishing if your coil is correctly wired and firing. Step 2 is spark distribution. I have been plagued over the last few years using new points and condensers yet still having issues as the parts are of crap quality.

kermit_rr · Apr 7, 2024

Check you haven't lost the middle out of the distributor and that is still springy or it might not be making contact with the rotor arm.
From a fellow positive earther

Rangieman123 · Apr 7, 2024

I was having a pint recently with a very old friend who has been working on classics for 50 years.
He's of the opinion that positive earth vehicles rust faster than negative earthed ones.
Any ideas on this??

Funonthefarm · Apr 7, 2024

kermit_rr said:
Check you haven't lost the middle out of the distributor and that is still springy or it might not be making contact with the rotor arm.
From a fellow positive earther

The pin is still there. The coil was new last year, is there a positive and negative type, or just the way is wired up? I’m wondering if I’ve blown the condenser wiring it the wrong way round?

kermit_rr · Apr 7, 2024

There's a + and a - but unless it's earthed (they haven't been for years) then it shouldn't matter
With a dead capacitor/condenser you still normal get some kind of spark
Are the points fully opening and closing?

Funonthefarm · Apr 7, 2024

kermit_rr said:
There's a + and a - but unless it's earthed (they haven't been for years) then it shouldn't matter
With a dead capacitor/condenser you still normal get some kind of spark
Are the points fully opening and closing?

Yea the points appear to be opening and closing, when taking the dizzy cap off they are at different positions, from closed to open. Have the multimeter on them and when closed reading 12.4v and when open 0…
And I’m getting spark on the ht from the coil… just not at the plug…

kermit_rr · Apr 7, 2024

Is the cap any good? Could be cracked or arcing inside

Funonthefarm · Apr 7, 2024

kermit_rr said:
Is the cap any good? Could be cracked or arcing inside

Cap looks perfect, contacts are clean and new.

Series 2 - won’t spark positive earth

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