Coil with Accuspark

[Dab_Hand]

Hi, I have been following the thread about the coil, and have a similar non starting 1974 mk4 spitfire.

The car just stopped a few weeks ago, and doesn't want to fire. Its a ballasted coil at 1.5 ohms with an Accuspark fitted  in distributor. I squirted some Easy Start in carbs, but no sign of life, although they have been off and serviced with new jets. There is a yellow spark from each plug earthed on the engine, and the distributor has not been touched, so at TDC timing mark rotor arm points to number 1.

A couple of weeks ago the starter motor was off, as I was getting clicking when I tried to start. Cleaned up engine earth and refitted starter and the starter motor is now  cranking engine ok. I was wondering if I caused a problem with the ballast wire bypass switch, but I can't find where this switch is. Is it in the starter motor? 

I measured 12v at the coil  + with ignition on, but drops to 9v when cranking. I put meter across coil -ve and +ve and get reading jumping all over. I wonder if the black wire to Accuspark is not being earthed via engine? Removed sensor and cleaned, but left a bit of thermal paste on it. Perhaps the Accuspark sensor is damaged? Is there any way to test this?

Any ideas welcome or tests I can undertake?

 

[johny]

The ballast wire/resistor bypass switch is the starter solenoid. Only when this is operated by the ignition key to start the engine a contact in it closes to put a full 12v supply to the coil while cranking...

[Dab_Hand]

Thanks Johny for replying to this post. I have a white wire on one side of the solenoid, and a white/red on the other side. Also white/yellow on +ve side of coil. When put ignition on get 12v on white/red then drops to 9v when cranking.  Why only 9v?

I am a bit lost about what to check next, so any help appreciated 

[johny]

Well cranking will drop the battery volts so not really a good test. Do the procedure I put in the other thread and take readings to identify exactly what youve got👍

[Pete Lewis]

with no load the ballast system can show battery voltages 

just how the accuspark does or does not do this  is not my best clues 

accuspark is cheap and can be good or troublesome  , i  seem to only see ones that have failed 

Pete

[Dab_Hand]

OK some fresh readings.

-ve of coil earthed, +ve of coil = 5.3/5.4 v. Battery at 12.2v.

All wires to coil disconnected coil resistance = 1.3/1.4 ohms. Accuspark measures open circuit.

So from this I assume this is a ballasted system.

Any thoughts what I  can check next?

 

[johny]

Right yes you have a ballasted system with the correct coil and hopefully youve have the starting boost supply from the solenoid working? For this there should be a yellow white wire connected at the solenoid which runs to the +ve terminal of the coil possibly via the ballast. This means when the starter motor is running you should see more than the 5.3/5.4v you measured previously at the coil...

Unfortunately as you have a ballast system unless you have new full voltage feed to supply your accuspark igntion (its red wire shouldnt be connected to the +ve of the coil but to a separate wire) then it will not be operating as recommended - not sure of the effect of this but better if wired as per manufacturers instructions...

[Dab_Hand]

Did a couple more measurements,  as wanted to see what happened before starter motor cranking.

So disconnected starter motor via thick wire at motor. Now able to measure the solenoid without cranking.

There is a white/yellow on +ve coil, which h measures 12.5 v with ignition on.

Pulled this wire to coil, and still measured 12.5v on this wire with ignition on.

Measured white/red on solenoid, and got 11.5v when solenoid pulled in.

 So maybe I need to swap some wires around?

Only had the car a few months, but was working OK, then suddenly  stopped.

[johny]

when you say 'ignition on' do you mean in cranking position? If so thats correct, 5.3/5.4v at coil positive with ignition switch on and then 12.5v (obviously wont be this high when starter motor actually turning) when in cranking position👍

[johny]

white red wire is solenoid operating wire from ignition switch when in cranking position

[johny]

What are you going to do about getting a full 12v supply for the accuspark from the ignition switch?

[Dab_Hand]

No the white/yellow seems to have 12.5v when ignition on, before reach  cranking position, even when pulled wire. So there seems to be a live feed 

[johny]

dont understand how you measured 5.3/5.4v volts at coil then!

[Dab_Hand]

The white/yellow is a 12.5v whi h goes to same +ve on coil, and attached to Accuspark  red wire

 

[johny]

oh you have two feeds to the coil +ve? A yellow white and whats the other, white?

 

[Dab_Hand]

No just the one white/yellow, and the red wire to the Accuspak.

Maybe I should take a photo?

 

[Pete Lewis]

the wjite /red is the trigger line to operate the solenoid  its on its own terminal at the sol.  dont try to use this for anything else .

the other white    should be a grubbywhite /pink trace this is the ballasted wire to coil pos.

and the white /yellow is the 12v bypass from the starter sol to coil pos.

Pete

Edited November 18 by Pete Lewis

[johny]

No its ok I can understand the yellow white and red on the coil +ve terminal but I dont understand how you measured 5.3/5.4v and 12.5v on the +ve terminal with the ignition switch in run position not start! Are you sure you didnt turn the key a bit further and thats when you got 12.5v reading? 

[johny]

You did this test with the coil -ve terminal earthed both times didnt you? 

[Dab_Hand]

No took that off a while ago, as didn’t want to heat up cable.

Just checked again, there is  a third wire to+ve coil, but this is only condenser wire (yellow).

The ign on / run position is easy to tell difference to cranking position, as you can hear solenoid clunk in

 

 

 

[Dab_Hand]

On pic, red wire is Accuspark, white is a spliced onto white/yellow. Condenser hides behind solenoid

[johny]

The tests are only valid if theres a flow of current through the coil so its -ve terminal must be earthed. Then measure the voltage to earth on the +ve terminal. It will be 5.3v in ignition switch run position and 12.5v in start position👍

[Dab_Hand]

Sorry, I confused myself.

Put earth back onto -ve coil, and measured 5.5v on +ve coil with ignition on, and 11.0v with solenoid pulled in.

(Charged battery up a bit, so variance in voltages)

 

[Pete Lewis]

that sounds about right, you can see the 5,5v on a bad day will drop below the operational volt range of most electronic units

pete

 

[johny]

Right thats good although dont know why you only got 11v as this should be full battery volts🤔 Anyway your ballast system seems to be working correctly so only leaves the problem of supplying the accuspark with 12v all the time rather than just when the starter motor is turning. I can see a white wire in you photo that goes to a relay on the bulkhead which I think is non standard - do you know what it does?