I’ve just had a slightly frustrating time getting a newly rebuilt engine to run. After checking connections, replacing condensers etc etc., the car seems sometimes to fire and run and other times refuses. Checking the points by separating them sometimes gives a strong spark other times nothing! I think the problem may be due to the quality of earthing to the distributor.
Has anyone had a similar problem and has anyone tried a separate earth lead to the distributor body?
For info this is a 6 volt system with DS4 distributor.
09-03-2023, 01:03 PM (This post was last modified: 09-03-2023, 01:04 PM by MartinH.
Edit Reason: Typo
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I had an intermittent misfire, particularly on bad road surfaces. An extra earth wire to the distributor body solved it completely. Belt and braces, it can do no harm.
The DS4 has to be able to rotate for advance/retard, which rather conflicts with the need for a good earth between the points and the engine block. You could just add an earth lead using a crocodile clip each end if you want to try things out before doing anything more permanent.
The lucas design of earthing the points base plate through on of the screws holding the whole plate down is not always reliable. I run a wire from the points base itself to a good earth elswere. I use one of the dynamo through bolts.
I had similar recurring engine failures until another forum member, GrahamO, found that there was poor earthing from the points to the distributor base plate. We resolved by soldering a wire onto the points base and running it to the condenser body. See the green wire in the photo. The long term solution was to install a new distributor base plate, because the screw threads for holding the points base were in poor shape.
Graham, I’m aware of problems with earthing the Bakelite base plate of DJ and DK distributors. I believe the earthing is reliant on a thin brass strip in the Bakelite and brass sleeves in the bolt holes. Eddie Loader wrote an article on this in both the Hereford and South Wales club magazines. However the DS4 has a steel baseplate and should have a good ground between it and the body.
As John says there is a requirement for the DS4 to rotate in the dynamo end piece to achieve advance and retard. This means there is no positive clamping position where an earth connection between the distributor and dynamo can be achieved and earthing is reliant on moving components.
It is good to know that others have used earth cables on the distributor and I will devise an earth cable route. As Jim has mentioned the head of the dynamo through bolt looks a good place to attach it.
Good point, Howard. I should have checked my distributor model before posting. Thanks for expanding on the baseplate faults in my model of distributor.
Regards
Graham.
