Distributor Question

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Jacksprat

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Sorry for posting so much on here, I am learning!

I am finding that the engine is faltering and believe that it is an electrical problem. On inspection of the distributor one of the two thin wires that come out the side of it has been damaged and is probably shorting onto the distributor. I am going to put some electrical tape on it and see if this cures the problem. Can anyone tell me what these thin wires are and what do they do?
 
One of the wires will come from the coil and the other may go to a capacitor on the side of the distributor. Any shorts would need to be fixed so I'd definitely start there.

The wire from the coil connects to the points inside the distributor and, when the points are closed, to ground through the distributor body. The opening of the points breaks the coils connection to ground causing the high voltage discharge from the coil to the spark plug via the HT leads and distributor cap.

The wire to the capacitor (condenser) connects the capacitor across the points (one side of capacitor is connected to the coil side of the points, the other side of the capacitor is connected to ground). The capacitors function is to reduce the spark across the points as they open. If either wire is shorting to ground (the distributors body is connected to ground) then the coil would not discharge and you would have no spark.
 
You can do a quick repair by fitting some heat shrink sleeve over it then shrinking it. It will have to go over the end conection but it will look quite neat and its tough.
 
doobie said:
One of the wires will come from the coil and the other may go to a capacitor on the side of the distributor. Any shorts would need to be fixed so I'd definitely start there.

The wire from the coil connects to the points inside the distributor and, when the points are closed, to ground through the distributor body. The opening of the points breaks the coils connection to ground causing the high voltage discharge from the coil to the spark plug via the HT leads and distributor cap.

The wire to the capacitor (condenser) connects the capacitor across the points (one side of capacitor is connected to the coil side of the points, the other side of the capacitor is connected to ground). The capacitors function is to reduce the spark across the points as they open. If either wire is shorting to ground (the distributors body is connected to ground) then the coil would not discharge and you would have no spark.
Click to expand...
That is extremely thorough and easy to understand, thank you.
 
Jacksprat said:
I think still has points..
Click to expand...

In that case, it's well worth making sure the contact faces are clean, and the gap is correct. This will also give you an opportunity to check the inside of the distributor cap for tracking marks, the carbon brush in the centre of the cap, and the condition of the rotor arm.
 
I only checked with a torch at night so need to have a proper look. I think that one of the contacts looked in poor condition so I think I will replace the cap. Thanks
 
There are two small wires inside the distributor:-
  • One of them connects the points contact to the condenser. Since both the points and the condenser are mounted on the moveable plate it seems unlikely that this wire would snap and fail.
  • The second wire, often called the "Dizzy lead" connects the points contact to the outside world and therefore the coil low tension side. The points are mounted on the moveable which is rotated a few degrees by the automatic advance/retard components, the weights and the vacuum bellows, consequently this is the lead which tends to be under stress from continuous bending. I've had this lead fail for this very reason on numerous vehicles in the past.
Since the condenser, points and a new dizzy lead shouldn't cost more than a tenner, I'd be minded to change the lot, reset the points gap and refit and re-time the distributor. Or convert it to an electronic contactless system.
 
Tall Ratbag said:
Does your distributor have points inside, or, has it been converted to electronic?
Click to expand...
Ratbag.. apologies I was wrong.. it has been converted to electronic with what looks like an accuspark kit. Sorry everyone I should have worked all this out first.. (two children under 3, starting a new business and a new (to me) Land Rover parked on a busy city street mean I don't get much time to lift the bonnet).

The damaged wire that I first referred to is in the thin black wire going to the coil. I think that it has been trapped between the cap and the distributor at some stage and will now definitely be shorting against the distributor.

I also had two minutes today to look in the distributor cap and the contact points are all in poor shape, I was able to scrape off some of the deposits with my finger. I read somewhere that electronic ignitions are particularly hard on caps and ht leads, is this true?

My plan now is to insulate the thin black wire to prevent it shorting and fit new rotor arm, cap and HT Leads.

Do you think this is the right course of action? do you think that I should replace the coil as well?

Many thanks again everyone for your help.
 
Always worth replacing the cap, arm and leads as they all deteriorate over time, they get hairline cracks and water gets in but they look OK. Our wifi reaches the road which is a lifesaver when (now 8) son wants to watch Lego vidoes in the drivers seat while I work under the bonnet - (until he presses the horn, that game is now banned..)
 
Parts are coming this afternoon. I have ordered a coil as well but not going to fit unless replacing the cap, leads and rotor arm doesn't do the trick. I will let you know I get on. Thanks.
 
Right I think that I have been a bit stupid.. I replaced the cap and rotor arm.. no difference, I replaced the leads.. no difference. I replaced the coil.. no difference. So I took out a spark plug and it was very black and one was a bit oily which is a bit of a worry.. although I am not going through oil quickly? Anyway long story short I cleaned up the plugs and gapped them and that sorted it! Obviously I should have checked the plugs first and I expect that everyone thought I would have already done that! Very stupid of me, hopefully this will remind anyone reading this in the future to have look at plugs before changing everything else!

Anyway I really enjoyed playing around with an engine again for the first time in 20 years and hopefully I don't have to suspect the electrics for a while! I am loving owning a series!
 
If any one is interested I thought that the black sooty plugs was probably to do with the mixture so was about to dive into adjusting the carb idle and mixture when I realised that the choke cable was sticking.. I must remember to check simple things first!!
 
Jacksprat said:
it has been converted to electronic with what looks like an accuspark kit.
Click to expand...

As above, replace or heat shrink the wires.
Might also be worth checking that the magnetic pickup sensor (red in diagram below) is as close to the reluctor (black thing around the shaft) as possible....place a piece of cellophane between them and move and tighten so they just don't touch.
I had loads of issues with mine as it was about a 0.5 mm off.
thXCJR8A9X.jpg
 
The gap between the reluctor and the pick up should be specified, its usually 0.010" (about 0.25mm). making the gap smaller increses the ramp up of the signal and advances the ignition slightly.
 
rob1miles said:
The gap between the reluctor and the pick up should be specified, its usually 0.010" (about 0.25mm). making the gap smaller increses the ramp up of the signal and advances the ignition slightly.
Click to expand...

This was the advice given by SimonBBC of PowerSpark who supplies ignition modules. I have not had issues since resetting it, but a quarter of a mm was about the thickness of the cellophane used (plastic film rather than actual cellophane) and on the PS distributor plate the screw settings make it impossible to push the pick up too close.
 
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