56 replies to this topic

[mullet]

No,you measure the dwell while cranking.The points when on the flat part of the dissy cam are closed and connects the coil to earth thro thedissy body.As the engine turns the points ride the love of the cam and open,disconnecting the coil and causing it to discharge thro the high tension lead.It does this a lot.The dwell is the percentage of the time they are closed(I think)
The rotor connects the spark from the cap center to the post of hopefully the correct plug.As I said it is very,very simple.Use Google,did I mention it is very simple.Enjoy,Steve..

Hey Steve.  Great expression: "ride the love of the cam".  Sounds like a 60s hippy song!  Thanks for the explanation!

[sonscar]

Auto correct sadly,should read lobe,Steve

[cal844]

The white pink is a seperate connection on the white wire, to the left side (as viewed when working from front of car) of the terminal, under the tape wrapping. Personally I'd strip this connection, change the coil for a normal 12v coil and run it seperate from the loom.


I have worked on 3 ballast resistor wired cars.


I will add that should the ballast wire get hot or melt it will take the rest of the loom with it.

Edited by cal844, 16 May 2023 - 07:38 PM.

[Lplus]

 

 

Hi LPlus.  Quite a newbie to electronics on this car I'm afraid (more into the mechanics side).  So forgive me, but what do you mean by "I take it you have cleaned and gapped the points if it has them?"?  If all the spade-connectors, I did clean them up and they all seem to fit snug.  Except that yellow/white (picture B), as cannot access it just yet.

The points inside the distributor under the distributor cap which open and close to make the coil produce a spark.  There's a capacitor in there too which is vital to the operation.  Of course it's possible you have some sort of electronic conversion, but I believe an '84 would normally have had a points type distributor.

 

Hi Lplus.  I think (apart from my own USB addition) that the wiring is original. I can never be sure, but just looking at components and wiring and how everything seems to be taped using the same tape, I think it's all original.  So based on the voltage and resistance readings, do you think we are narrowing it down to the distributor?  As this all kicked off with the jumpstarting, could the capacitor be damaged?  Is their a way to know, or should I take the distributor out?

 

I hesitate to point to the distributor with certainty, but since it is vital for the spark and you haven't inspected it, it is worth doing so.  It is not necessary to remove the distributor, just take the cap off and you should see the contact points and the capacitor. Check the points first and either clean up or renew if they're too eroded.  It's worth fitting a new capacitor at the same time if you're renewing the points.  One other check would be to measure the resistance of the coil HV circuit from the body of the coil to the HV outlet in the middle.  It seems unlikely to have failed but it might be worth a check. Tthe resistance should be in the thousands of ohms but not open circuit.

as to the jumpstarting, unless you used a 24 volt battery or connected it up back to front, I can't see how it can have damaged the electrics.

 

[mullet]

 

 

 

Hi LPlus.  Quite a newbie to electronics on this car I'm afraid (more into the mechanics side).  So forgive me, but what do you mean by "I take it you have cleaned and gapped the points if it has them?"?  If all the spade-connectors, I did clean them up and they all seem to fit snug.  Except that yellow/white (picture B), as cannot access it just yet.

The points inside the distributor under the distributor cap which open and close to make the coil produce a spark.  There's a capacitor in there too which is vital to the operation.  Of course it's possible you have some sort of electronic conversion, but I believe an '84 would normally have had a points type distributor.

 

Hi Lplus.  I think (apart from my own USB addition) that the wiring is original. I can never be sure, but just looking at components and wiring and how everything seems to be taped using the same tape, I think it's all original.  So based on the voltage and resistance readings, do you think we are narrowing it down to the distributor?  As this all kicked off with the jumpstarting, could the capacitor be damaged?  Is their a way to know, or should I take the distributor out?

 

I hesitate to point to the distributor with certainty, but since it is vital for the spark and you haven't inspected it, it is worth doing so.  It is not necessary to remove the distributor, just take the cap off and you should see the contact points and the capacitor. Check the points first and either clean up or renew if they're too eroded.  It's worth fitting a new capacitor at the same time if you're renewing the points.  One other check would be to measure the resistance of the coil HV circuit from the body of the coil to the HV outlet in the middle.  It seems unlikely to have failed but it might be worth a check. Tthe resistance should be in the thousands of ohms but not open circuit.

as to the jumpstarting, unless you used a 24 volt battery or connected it up back to front, I can't see how it can have damaged the electrics.

 

"connected it up back to front".   I had a felling something got fried due to the jumpstart, but it seemed fine afterwards for 2 drives.  But gradually got worse now doesn't start.  I wonder if I made a stupid error like this.

[mullet]

Hi all.  Sorry for the late reply as had to travel.

 

I replaced the distributor cap about 4 years ago and have done very little driving.  I took the cap off for a couple of photos. Looks good, but I am guessing on appearance not much can be established about its condition.

 

I feel a bit out of depth here.  Could I try:

1) "jumping" over a potential damaged wire temporary to see if it starts?

2) buy new like-for-like components of a possible culprit, and replace one by one until the problem is solved? (I know, possible unnecessary cost, but cheaper than garage I expect and all the parts are old...note all distributor cables, spark plug cables, and cap are only 4 years old so I guess OK)

3) failing that, when my mechanic neighbour has time (probably not for months now), I'll ask him to look at the above suggestions (eg, changing the ballast set up).

 

Any thoughts on the above?  Sorry for being so thick here!

 photo_2023-06-13_19-20-29.jpg   37.08K   0 downloads  photo_2023-06-13_19-20-40.jpg   19.57K   0 downloads

[sonscar]

With the cap off turn the engine over and check the points actually open and close,Steve..

[mullet]

With the cap off turn the engine over and check the points actually open and close,Steve..

Thanks Sonscar.  If I understand, I will see if it does this?  I'll get my wife to turn it over tomorrow while I look to see what happens....

https://youtu.be/sV_X7Z9WY78

Actually the above seems like a good video in general for me!  This also looks good

 

Quite a lesson.
 

[mullet]

With the cap off turn the engine over and check the points actually open and close,Steve..

Hi Sonscar.  The points open and close.  No spark seems present (although it is in daylight); would a spark be expected when the cap is off?  I cannot upload the video.  But I have the video on this link if it works for you?  https://1drv.ms/v/s!...cWHuCD?e=C3GEjm

 

Does it offer any clues?

[sonscar]

Get a bulb holder or test lamp.Connect one side to the engine and the other to the coil positive.manually open the points.The bulb should light with them open and go out when closed.If it fails to light disconnect the wire to the dissy at the coil and it should light.If it does not light remove the positive wire from the coil and connect to it and it should light.Failure here is no supply to the coil.Ignition needs to be on.Steve..

[Designer]

Hi Mullet,

Have you checked the Low Tension side of the circuit. In the left hand picture above there is a black wire coming out of a rubber grommet top right hand corner of the picture.

This black wire is about 4 to 6 inches long before it connects to a coloured wire, off hand I cannot remember the colour of this I think it is black with white stripe. Pull the black wire out from this connector which will expose the male spade part of the connector. Connect a piece of wire from this spade connector to the negative side of the coil. Try starting the engine again. if it starts it means there is a bad section in the Low Tension side most probably the connector you have just separated.. Give it a thorough clean both male and female parts. Then try starting the engine again to make sure that that was the problem. Also check the connection on the negative side of the coil is clean.

[mullet]

Get a bulb holder or test lamp.Connect one side to the engine and the other to the coil positive.manually open the points.The bulb should light with them open and go out when closed.If it fails to light disconnect the wire to the dissy at the coil and it should light.If it does not light remove the positive wire from the coil and connect to it and it should light.Failure here is no supply to the coil.Ignition needs to be on.Steve..

@Designer.  Thank you.  I made a "jumper" cable but made no difference (I also cleaned up all connectors I could reach when the problem started).

 

@Steve.  Thanks again.  I made a lamp from a spare car bulb.  Here are the results with CAPS being my text....

Get a bulb holder or test lamp.Connect one side to the engine I CONNECTED TO GROUND CABLE FROM ENGINE and the other to the coil positive.manually open the points.The bulb should light with them open and go out when closed LIGHT STAYS ON WHETHER POINTS TOUCH OR NOT, AND STAYS AT THE SAME BRIGHTNESS.

 

If it fails to light disconnect the wire to the dissy at the coil I DISCONNECTED THE 2 BLACK/WHITE SPADE CONNECTOR CABLE AT THE COIL NEGATIVE (WHICH IS THE ONLY WIRE THAT GOES TO THE DISTRIBUTOR FROM COIL AS I JUST TESTED WITH DESIGNER'S ADVICE) and it should light YES LIGHTS (OR RATHER, STAYED LIT).

ALTHOUGH IT LIT, I CONTINUED TEST.......

 

If it does not light remove the positive wire from the coil and connect to it  and it should light.  BY REMOVING PINK/WHITE AND YELLOW/WHITE THE LIT BULB THEN GOES OFF, EVEN THOUGH LAMP IS CONNECTED TO POSITIVE OF COIL.

 

Failure here is no supply to the coil.Ignition needs to be on.

 

I DID OTHER TESTS FOR THE HELL OF IT....

   ALL REMOVED FROM COIL BUT FOR TEST LAMP AT POSITIVE AND LIGHT GOES OFF

   YELLOW/WHITE PINK/WHITE CONNECTED WITH LAMP ON POSITIVE TOO FOLLOWED BY REMOVING NEGATIVE-TO-DISTRIBUYOR MAKES LIGHT MUCH MUCH BRIGHTER

FINGERS CROSS THIS HELPS?

[sonscar]

The points earth the coil charging it up.The light not dimming would indicate that they are not doing this.Check the wire from the coil negative to the points for continuity and clean and regap the points.They earth through the base plate which has a short braided wire joining the moving and fixed parts.Enjoy,Steve..

[Designer]

Hi Mullet,

Just another thing to try. Remove the distributor cap, remove the rotor arm and smear a very thin layer of toothpaste or use threadlock if you have it on the top of the rotor. Replace the rotor arm without touching the paste and very carefully replace the distributor cap. No need to lock it in place just make sure it is fully seated in its correct position. Remove distributor cap and check  to see if the paste or threadlock has been transferred onto the centre pin of the cap. If it hasn't then this is the problem but why I do not know, it could be that the centre shaft of the distributor has dropped for some reason or the centre pin of distributor is not long enough. Obviously clean the paste/TL off the rotor and cap centre pin afterwards. It has to be a paste as the distributor is on an angle anything thinner is likely to run off.

If this is the case then as a temporary fix pack the inside of the rotor arm with something suitable, ie kitchen foil, to raise the rotor arm up to meet the centre pin.

 

Regards Paddy

[mullet]

Hi Mullet,

Just another thing to try. Remove the distributor cap, remove the rotor arm and smear a very thin layer of toothpaste or use threadlock if you have it on the top of the rotor. Replace the rotor arm without touching the paste and very carefully replace the distributor cap. No need to lock it in place just make sure it is fully seated in its correct position. Remove distributor cap and check  to see if the paste or threadlock has been transferred onto the centre pin of the cap. If it hasn't then this is the problem but why I do not know, it could be that the centre shaft of the distributor has dropped for some reason or the centre pin of distributor is not long enough. Obviously clean the paste/TL off the rotor and cap centre pin afterwards. It has to be a paste as the distributor is on an angle anything thinner is likely to run off.

If this is the case then as a temporary fix pack the inside of the rotor arm with something suitable, ie kitchen foil, to raise the rotor arm up to meet the centre pin.

 

Regards Paddy

Hi Paddy. Thanks.  I just tried this and there's definitely no gap.  I took the opportunity to sand stuff down too (there was black on the rotor arm, but it appeared to be melted plastic rather than carbon from the distributor cap, which is pretty new).  Tried to start and again, no luck.

 

As I am short on equipment (eg, checking the gaps) I hope someone who knows more than me will go through it while I shadow them.  I'll update this again soon!