Technical Is my coil wired up the wrong way?

[Noah500]

I'm just about to try to fit my Powerspark electronic ignition so I thought I would double check the wiring first.

On my Marelli coil there is one black wire going from the terminal marked 16 and +B to the distributor, and one blue wire attached to the terminal marked D. From what I can tell from the wiring diagram, the blue wire comes from the fuse box so should be powered and therefore go to the + terminal? However, there are no other wires than the black one going to the distributor so if I swap them round would any power get to the distributor?

The current wiring (with points setup) does work, so now I'm confused. The Powerspark instructions say the new red wire goes to the + terminal along with a wire ”from the ignition switch”...

 

[Noah500]

Voltmeter shows 12V from the blue wire i.e. NOT on the + terminal.

 

[Noah500]

So, is there supposed to be no + wire to the distributor?

 

[Noah500]

There's also a black wire from the bottom of the condenser to the terminal with the black wire on the distributor body

 

[Goldnrust]

Yes, your coil appears to be wired backwards! A backwards coil may still work, but at considerably reduced spark output.

With points you should have +12 going to the positive side of the coil and a single wire from the negative side of the coil to the points. The points are 'passive' and when they close they just connect the negative side the coil through the distritubter body itself to the engine ground.

Electronic pickups, like the Powerspark kit, are 'active' and therefore need a 12v supply to power their electronics and a negative supply through the distributer body and then output a signal along the wire to the negative side of the coil.

The condenser should be connected between ground (it may be grounded through it's mounting point/bracket) and the negative side of the coil.

I would be tempted to swap the coil wiring over and go for a test drive before fitting the electronic ignition, if only for testing purposes to understand whether the coil polarity was actually the root of the problem or not.

 

[Noah500]

Thanks... sounds like it was as I suspected. I was going to try swapping the coil wires before trying the Powerspark in any case but thanks for the confirmation. Since the condenser has a wire coming out of the bottom I assume that is an earth. I'll try it and see

 

[Noah500]

Reversed the wires on the coil and it starts and runs!

 

[Toshi 975]

Can you confirm where you have connected the condenser wire to, it should go to the low tension connection on the distributor.

 

[Noah500]

I just reversed the connections at the coil end. The short black wire from the bottom of the condenser (the only wire on the condenser) was connected to the bolt that comes out of the distributor in the plastic bush thingy. There was another black wire going from there to the coil - originally to the +ve side, then to the -ve side after I swapped them. Then engine started and ran like that

 

[Noah500]

To be clear:

Before I started, the wiring was:

• Blue wire to -ve side of the coil
• Black wire from +ve side of the coil to the removable bolt (in a plastic bush) which goes through the body of the distributor - is that the " low tension connection on the distributor"?
• Black wire from that bolt to the bottom of the condenser

No other earth wires or anything from the coil or the distributor

Afterwards, I changed it to:

• Blue wire to +ve side of the coil
• Black wire from -ve side of the coil to the removable bolt (in a plastic bush) which goes through the body of the distributor
• Black wire from that bolt to the bottom of the condenser (no change)

 

[Noah500]

From :| to ... after going for a drive on Friday with the Powerspark fitted, then taking the car out of the garage yesterday. when I went to put it back in the garage it wouldn't start. I tried moving the distributor round in its mounting hole but nothing.

This morning I checked that the HT leads were on, that the magnet thingy inside the distributor was pushed on well, and reset the static timing to 10° BTDC using the marks on the pulley and it still wouldn't start.

I rechecked the resistance across the coil (>3Ω) and the power supply at the coil - both OK but it still wouldn't start.

Retried starting, adjusted the timing at the distributor by loosening the nut underneath - still nothing.

Now, it seems like there is no power at the coil with the ignition on, not a sausage. I checked the relevant fuse and that's OK, and there is 12V at both sides of Fuse 2, so that's not the problem.

I'm hoping that it isn't the coil feed wire that's buggered, because that would be a pain to find the break and fix/replace but any ideas on what else it might be?

It's really frustrating because it was starting and running with the Powerspark at one point, though not 100%.

 

[Noah500]

Further update: there is power at the coil but nothing shows on the voltmeter if I put the black (negative) probe on the negative terminal of the coil so somehow the circuit is not complete. The circuit is completed if I touch the black probe onto the body of the coil.

Not sure why this should 'suddenly' have happened when previously there was continuous circuit across the coil terminals. It's odd that there is still resistance across the coil terminals (3+Ω). I am tempted to put an earth wire from the coil negative terminal to a body point, except that the Powerspark No Spark troubleshooting instructions say "Ensure that there is only the Black wire on the negative side of the coil (this wire can provide an unwanted earth for the electronic system and result in no spark, if this is your tachometer/rev counter then remove for testing)". May be OK to test, though

??

 

[Noah500]

OK - I tried a direct earth from the coil to a body point and then there is no resistance in the coil, though there is 12V cross the coil, as expected.

Reset (again) the distributor 10° BTDC and the rotating thingy inside the distributor to point to the engine and now when cranking there is occasionally a stuttering half firing...

 

[Goldnrust]

The negative side of the coil should only be earthed when the coil is charging for those handful of milliseconds before it fires.

So the negative side should only be connected to the points / Powerspark unit.

Have you pulled a plug and turned the engine over physically checking for spark? Before you go round in circles hunting for a lost spark that might not be lost.

 

[Noah500]

Yes, I did that and there is a spark

 

[Goldnrust]

Then it does sound like timing might be the issue. As far as I know, there's no reliable way to static time the Powerstark units. What you really need is a timing light, do you have one?

Whilst it's much easier with the car running, you should still be able to use one to see how far out the timing is while cranking on the starter motor.

 

[Noah500]

No I don't but think I need one

 

[Noah500]

Today I got my tame mechanic/service guy to come round to the house (great guy, his workshop is only a couple of minutes away and I've been using his services for >20 years) and he set up the timing so it starts and seems to run OK though with his timing light the dynamic timing seemed to be advanced way more than the 10+18 degrees (he thought maybe his light is not suitable for 2 cylinder cars...?? or maybe he didn't rev it to 3000 rpm. Who knows). I'll take the car out to see how it feels in practice. I've also ordered a timing light from Powerspark (where I got the electronic unit and leads from) and I will see what results I get.

 

[Noah500]

I got a timing light from PowerSpark and it also shows the timing advanced way too far. Today I finally got round to adjusting the timing on the slot on the distributor and I've got it to show 28° using my Fiat copy timing plate. It also sounds smoother (as much as a 2 cylinder can ever be smooth) so I'm hopeful that it's now OK