12 replies to this topic

[DanJones96]

My dizzy is pumping out a constant earth from the black wire that comes out of it regardless if the points are open or shut. Ive tested with a power probe and even isolating the points contacts everything is earthed. The condensor is what's earthing everything.. I've tried another condensor but its doing the same.. Is it possible both condensers are broken and leaking earth? Do i possibly have an isolation piece missing?

Thanks
Dan

[gazza82]

The plastic 'washers' on the connection point to the points are easy to mix up ..

[DanJones96]

I dont think this is the issue.. Even with the points completely removed the condenser is letting an earth through to the black output wire. It can only be either the inside of the condenser or a missing isloation piece imo?

[Ethel]

The condenser is just a capacitor, no current should flow through it, but it will "soak up" a little bit while it charges. Probably enough to fool a low power device like a meter.

[David128]

try using a test lamp

[DanJones96]

I will try a bulb later but its just strange that with the points wide open the black output wire from the dizzy is constantly earthed. surely that output wire should only be earthed when the points are closed?

[DanJones96]

Tried a lamp.. As expected it was lit up the whole time its defiantly a closed curcuit comstantly, even when turning over its just constant earth.. Ordered new points and condenser hopefully they arrive within the next 1-2 hours

[mini13]

yeah crap condensor,

 

basically a condensor is two large plates, one with he black wire connected and one with the case connected, when a voltage is applied an electro static charge builds up between the plates, and when diconnected the charge wants to flow out of the plates... kind of like a battery but faster acting. this effect is used in smoothing voltages, and in the case of points it prevents the points arcing and burning out....

 

in condenders the two plates are rolled up foil with a thin insulator between them, often aluminium with one side anodized to make it non conductive... if this insulation breaks down ( usually from over voltage or heat) the capacity will decrease or totally short out.

 

Unfortunaltly moder condensors are pretty crappy in terms of quality and fail quite often... always carry a spare, and spare points!

[dklawson]

Gazza82 made a point that I would like to follow up on.

 

What distributor is this?  If it is a 23D or 25D series, there are insulators that have to be located correctly of the points and condenser will appear permanently shorted to earth.

 

When you made your resistance measurements, was the condenser's black wire disconnected... were you measuring resistance from the disconnected black wire to the metal shell of the condenser?

[DanJones96]

43D dizzy... I have got some new points but an interesting thing they were from a rover mgb st1. I now have a spark but not starting. I have spark compression and fuel

[sledgehammer]

if you disconnect the condenser , does the engine start ?

 

it will run rough - due to points sparking - so don't run for long , otherwise they will burn 

 

as above - condensers are now carp - buy 2 , 1 as a spare

Edited by sledgehammer, 19 March 2016 - 05:04 PM.

[DanJones96]

Do i need to do this test even if im getting a spark?

[dklawson]

Where are you observing the spark... at the points or at the spark plugs and what color is the spark?

 

When did this engine last run and what has been done to the engine?