Sparking Problem '72 MkIV Spitfire

[Will It Ever Run Again]

Hi all,

I have fitted a brand new loom on a '72 MkIV Spitfire together with a new switch and electronic ignition (Powerspark - the entire dizzy and a compatible coil). I cannot get a spark.

This is my understanding of the relationship between starter solenoid, ignition coil and ballast resistor on a standard points car with 6V coil (not electronic ignition):

Battery sends power to solenoid which, via brown wires, sends power to the switch. When cranking, power comes back to the solenoid via red/white wire which sends it on to coil +ve via white/yellow wire. When not cranking, but running, the power comes via a white wire to a ballast resistor (to reduce voltage) then onto coil +ve via another white/yellow wire.

Is that correct?

With electronic ignition I understand there's no need for the ballast resistor. A 12v coil is used. Do I still need the white/yellow from the solenoid to the coil +ve for cranking or is it unnecessary?

The engine does turn over so I assume the solenoid is earthed ok and the switch is working. Is that a correct assumption? My solenoid has a main battery connection with spades off to left and right of that. On those spades are brown wires into the loom. There's a main connection to the starter. There are two further spade connections, one on either side. I have a red/white wire on the left one and white/yellow on the right. I have read I can check if there's a 'click' from the solenoid when, with all connections to it removed, except for battery cable, I connect a wire from battery +ve to these spades junctions one at a time. The one that creates a click is the correct spade for the red/white wire. I am yet to check this. Could I have a duff solenoid?

I have tried numerous wiring configurations but cannot get a spark. I am using a spark tester (which goes between HT lead and spark plug and lights up when a spark would be present and have tested it on another Spit that runs). I have swapped the coil with another Spit (a 1500) with electronic ignition and it ran on that car fine. 

Is it right that the red/white wire only have power during cranking? That makes sense but how do I test that it does?

What am I missing? It's completely frying my brain at the moment and any help would be greatly appreciated! I can take pics if it helps.

Thanks,

Steve

[thescrapman]

All you theories seem right.

to test 12v cranking only feed, which is the spade opposite the one that triggers the solenoid, remove output lead to starter as you do not want engine turning at this stage, put a bulb on the cranking only spade, and then turn ignition key and see it bulb comes on when you get to stater position.

[RobPearce]

If you have a 12V (3ohm) coil then you do not connect any of it to the solenoid. Leave that extra terminal unconnected and remove the white/yellow wire. Remove the ballast resistor. Connect the white (ignition switched) wire directly to the coil and to the distributor pickup/amplifier supply as directed by the installation instructions. Check that this white wire has 12V on it when the ignition is switched on.

If you are keeping the ballasted coil, leave all the coil and solenoid connections as they are. Take a white feed from the "top" end of the ballast resistor (i.e. the ignition switch) to the amplifier supply.

If the pickup amplifier is trying to be a single wire device, powered through the coil, then it won't work with a ballast system. I don't know how many of them are designed like that, though.

If your engine turns over you don't have a duff solenoid. It's possible for only the ballast bypass contact to fail but it's rare and usually harmless. There is no point trying to diagnose the solenoid - it's not the problem.

[Will It Ever Run Again]

4 hours ago, thescrapman said:

All you theories seem right.

to test 12v cranking only feed, which is the spade opposite the one that triggers the solenoid, remove output lead to starter as you do not want engine turning at this stage, put a bulb on the cranking only spade, and then turn ignition key and see it bulb comes on when you get to stater position.

Thanks so much for your comment. 

A bit confused about the spades you mention. So you mention 'cranking only feed' - is that then the red/white wire? I understand that this wire is only live when cranking and feeds the solenoid. But I also assumed then that that 'triggers' the solenoid? But then you say the cranking feed is opposite the one that triggers it. Sorry not really looked at solenoids much until this issue arose. Thanks

Edited August 24, 2021 by Will It Ever Run Again

[Will It Ever Run Again]

3 hours ago, RobPearce said:

If you have a 12V (3ohm) coil then you do not connect any of it to the solenoid. Leave that extra terminal unconnected and remove the white/yellow wire. Remove the ballast resistor. Connect the white (ignition switched) wire directly to the coil and to the distributor pickup/amplifier supply as directed by the installation instructions. Check that this white wire has 12V on it when the ignition is switched on.

Yes I have a 12v coil which is suitable for the elec dizzy. The dizzy has two wires, one red one black. These I believe go to +ve and -ve coil terminals respectively. So if that's right the dizzy gets its power via the coil and not direct from the white wire. Does that sound right?

3 hours ago, RobPearce said:

If you are keeping the ballasted coil, leave all the coil and solenoid connections as they are. Take a white feed from the "top" end of the ballast resistor (i.e. the ignition switch) to the amplifier supply.

I'm not but I'm interested in how it should be set up on a standard car just for future projects. When you say 'top end' what do you mean? It had white wire (live 12v with ignition on) coming in to ballast and then yellow/white coming out the other end (I assume it makes no difference which way through the ballast the voltage runs?). 

And sorry what do you mean by a 'Pick up Amplifier'? I assume you're talking about some part of the elec ignition set up. And I agree they don't work well with the ballast resistor. I had tried to get a spark without the ballast (ie white 12v direct to coil) but not quite in the way described above so I will have another go and report back.

Many thanks indeed for your help.

[RobPearce]

1 hour ago, Will It Ever Run Again said:

The dizzy has two wires, one red one black. These I believe go to +ve and -ve coil terminals respectively. So if that's right the dizzy gets its power via the coil and not direct from the white wire.

OK, the electronics has a third wire, the ground, which is connected inside the disi. The red goes to the +ve coil terminal, which also has the white wire, so it is being fed directly from the white wire. The black goes to the other coil terminal, which may have a wire to feed the tacho, if it's a late car, but probably doesn't have anything connected on a 1972 model. That's where the points on a conventional disi were connected to.

1 hour ago, Will It Ever Run Again said:

When you say 'top end' what do you mean? It had white wire (live 12v with ignition on) coming in to ballast

Yes, that white wire is the "top" - it's the supply from the ignition switch so would conventionally be drawn at the top of a schematic wiring diagram, although vehicle wiring diagrams don't always follow that convention.

1 hour ago, Will It Ever Run Again said:

And sorry what do you mean by a 'Pick up Amplifier'? I assume you're talking about some part of the elec ignition set up

The pick up amplifier is the electronics in an electronic disi. It replaces the points, senses ("picks up") the shaft position either magnetically or optically, then amplifies that signal into the high current needed to switch the coil.

[Will It Ever Run Again]

Fabulous thanks.  All makes sense. I'll give the suggestions a go tomorrow. Way too busy today with kids back at school in the morning!

I will report back.

Steve

[thescrapman]

9 hours ago, Will It Ever Run Again said:

Thanks so much for your comment. 

A bit confused about the spades you mention. So you mention 'cranking only feed' - is that then the red/white wire? I understand that this wire is only live when cranking and feeds the solenoid. But I also assumed then that that 'triggers' the solenoid? But then you say the cranking feed is opposite the one that triggers it. Sorry not really looked at solenoids much until this issue arose. Thanks

Cranking only feed is the one that goes live at same time that engine is cranking. And provides the 12v to bypass ballast.

it is a separate contact inside solenoid, it it was paired with red / white trigger wire it would lock starter on by back feeding via ballast resistor.

[Will It Ever Run Again]

On 24/08/2021 at 20:50, thescrapman said:

Cranking only feed is the one that goes live at same time that engine is cranking. And provides the 12v to bypass ballast.

it is a separate contact inside solenoid, it it was paired with red / white trigger wire it would lock starter on by back feeding via ballast resistor.

I get it that on cranking, the ballast is bypassed but I'm not sure I fully understand what you said there. Are you saying the red/white is or isn't the one that goes live on cranking? I thought it was.

As per comments above I now have white wire direct to +ve on coil, no ballast and no yellow/white from solenoid as I have electronic dizzy and 12v coil. I have red/white to solenoid and other than battery, starter and several brown wires there are no others to the solenoid.

I have tested my spark tester, the HT lead from coil to dizzy, the HT leads and the coil. All good. Still no spark. I also tried getting one between the end of the lead from the coil and earth but couldn't even though that lead works fine on another car. 

The coil has a 12v reading at both positive and negative terminals with ignition on. I assume this is ok as this is also the case with my other spit which works well. The wires to the coil +ve are red from elec dizzy and the white power wire. To the -ve terminal is just the black from the dizzy.

If I had hair I'd have pulled it out so if anyone can help resolve this I'd be rather chuffed.

Thanks 

Steve

[Will It Ever Run Again]

I should also say the car turns over fine

[RobPearce]

4 hours ago, Will It Ever Run Again said:

Are you saying the red/white is or isn't the one that goes live on cranking? I thought it was.

The problem is that the description is insufficiently specific.

The white/red wire goes live when you attempt to crank, because it's fed from the ignition switch, which connects it to live when you turn the key. It controls the solenoid.

The white/yellow goes live when you are cranking, because it's fed from an extra terminal in the solenoid.

While this may seem a matter of fine pedantry, it is actually a very important distinction. If the white/yellow were merely connected directly to the white/red then the solenoid would be activated by the coil feed whenever the ignition was on. If it were connected to the main solenoid contacts (starter motor connection) then the low resistance of the starter motor would kill the engine as soon as you released the starter. It has to be a separate, extra contact on the solenoid "output" side.

[RobPearce]

4 hours ago, Will It Ever Run Again said:

The coil has a 12v reading at both positive and negative terminals with ignition on. I assume this is ok as this is also the case with my other spit which works well. The wires to the coil +ve are red from elec dizzy and the white power wire. To the -ve terminal is just the black from the dizzy.

OK, ignition on and engine not turning, the coil has 12V applied on one side and probably and open circuit on the other, hence also 12V through the coil. (On a car with points, this may be 0V because the points are closed, depending where the engine stopped, but many EI units incorporate a protective timeout to ensure the coil is off in this condition).

The question is what happens while you're cranking. Connect a small bulb (a dashboard light, for example) across the coil. Crank the engine over. If the light does not flash then there's a problem with the low tension side, probably the EI unit. Try a bulb in the place of the coil (i.e. disconnect the coil, put an indicator bulb in its place). If this flashes then the EI is failing to drive the coil load. If not then it's just not working at all. It may not be properly earthed inside the disi, or it may have been fried.

[Will It Ever Run Again]

Awesome thanks Rob and everyone else. I did a bench test between coil, dizzy, battery and a spark plug and with a different distributor, when turning the shaft, I got a spark. With this one I've had trouble with I didn't (I even did a video about it!). I contacted the supplier and they asked me to do another simpler test on the car with a test bulb between the black lead from the dizzy and the +ve on the coil. When turning over the bulb should light which it didn't so it seems the brand new distributor is duff and they're sending me another.

Edited September 7, 2021 by Will It Ever Run Again

[yorkshire_spam]

Result!

[Will It Ever Run Again]

Just to finish this off, I rec'd another module in the post and with it fitted got a spark first time. Whatta you know!!

Within a few minutes it was running, albeit extremely fast so I need to do some adjustments. But at least I now know not to trust brand new parts! I also now have two tests for an electronic distributor which may save me time on future cars.

Thanks all!!