13-08-2024, 08:03 PM
(13-08-2024, 08:11 AM)John Cornforth Wrote: Hi again
At risk of telling you stuff you know, check that the sprung loaded carbon button in the centre of the distributor cap is present and correct. Since your malaise seems to affect all cylinders, the finger of suspicion is pointing to the king lead and its connections, and the rotor arm.
The rotor arm tip should run pretty close to the contacts, I guess no more than a 20 thou gap would be in order. This needs a spark to jump it, but with such a small gap and only atmospheric pressure the voltage loss is acceptable. Watch out for caps where the four electrodes have eroded away. The rotor arm tip should ideally also be unworn and have nice sharp edges.
I have seen cases where the rotor arm tip has actually touched the contacts, leading to rapid wear and a film of brass filings inside the cap. This can happen if the shaft bearings have worn enough to give appreciable side play, or where mix and match caps and arms have been fitted and there has been a build up of tolerances.
Thanks for all the help, John. All the caps have brass, not aluminium inserts and are a mix of perfect condition original brown types and new black ones.
This time I swapped the first failed distributor but complete with its cap and wires to another 7 and it ran. So did the reserve unit - so, nothing to do with the original cap or HT leads.
I then tried each of the non-working units with an earth wire from their bodies directly to the battery - with no result. I then fitted a DK4 that I'd assembled, but that didn't work either - so I tried the earth wire to that and, hey presto, it ran. I then removed the earth wire to see if would work (why should it?) but it did - and has continued to do so. So, what the problem is I've no idea.