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+--- Thread: Mystery ailment (/showthread.php?tid=7938)
Mystery ailment - David Cochrane - 18-08-2022
Hilda, our ridiculously unreliable RP saloon, has come up with yet another way to plague her long-suffering owners. After doing 600 miles this year with only a broken contact breaker points heel, dodgy rotor arm & distributor cap, intermittent main fuse, suspected blocked oil jet, stuck advance & retard mechanism, indicators flashing at double-speed, leaking head core plug, rubbing rear brake and a rear spring pin halfway out, her latest trick is: after about a couple of miles the engine cuts out for 3 seconds, then continues for about 6 seconds, then cuts out for 3 seconds, then resumes for 6 seconds, and so on.
It's not (or unlikely to be) fuel, as the SU float chamber has petrol and fuel problems tend not to be on/off like this is. I have changed the condensor which made no difference. Before I try changing the coil, has anyone come across anything like this before?
David
RE: Mystery ailment - JoeRowing - 18-08-2022
check the:
Fuel filter,
points,
coil,
distributor lash,
king lead insulation
RE: Mystery ailment - Ruairidh Dunford - 18-08-2022
Sounds like an ignition wire fault - in the switch.
This is the kind of thing that will instantly kill electronic ignitions, which I think you had some trouble with too.
Run a live wire from the battery to the coil and see if it remains. Worth a try.
RE: Mystery ailment - john williams - 19-08-2022
David, I had a similar fault on a RM, a while ago. It turned out to be a poor electrical connection on the coil SW terminal. Just a thought.
RE: Mystery ailment - Damian GT - 19-08-2022
Hi David, FWIW I would change the coil. Simplest way of excluding it as a cause?
RE: Mystery ailment - Peter Naulls - 19-08-2022
I had something like this with one of those red-key battery isolators.
RE: Mystery ailment - John Cornforth - 19-08-2022
Hi David
I have a suggestion for testing the ignition switch / coil feed whilst driving. Wire up a small 6 volt bulb between the Switch terminal of the coil and Ground, and place it somewhere easily visible whilst driving. This way you may be able to "catch it in the act", i.e. see if the bulb goes out at the same time as the engine dies.
The ignition switch part of the PLC switch does eventually wear and can become a little intermittent after 80 or more years. You may even find that the bulb flickers a bit as you turn the key, which is a sign of wear.
On the subject of red-key battery isolators, of the three I have tested (at high current) all have shown inconsistent contact resistance and I wouldn't trust any for use on a 6 volt car.
RE: Mystery ailment - John Mason - 19-08-2022
Hello David, The thing that puzzles me is the three then six second recurring stop start of the engine. Could it be a faulty coil that once warm fails then takes three seconds to cool enough to re start but after six seconds is to hot again and fails. Then the cycle just keeps repeating. Just another point. It could be the condenser that is doing this for the same reasons.
John Mason.
RE: Mystery ailment - Denis Sweeney - 19-08-2022
Talking condensers, between my brother and myself we have had 5 new condensers that have failed within the last four months. These have been purchased through our normal suppliers with the exception of the last which failed within less than 10 miles on the clock and this was procured from a distributor specialist.
Having just rebuilt my distributor and taking Ruby out for a run to the local A7OC meet it failed within five miles from leaving home. Replaced with yet another new one.
RE: Mystery ailment - Tony Griffiths - 19-08-2022
(19-08-2022, 11:02 AM)Denis Sweeney Wrote: Talking condensers, between my brother and myself we have had 5 new condensers that have failed within the last four months. These have been purchased through our normal suppliers with the exception of the last which failed within less than 10 miles on the clock and this was procured from a distributor specialist.I wonder...these Chinese-made lumps of rubbish - are they simply being overloaded and two or more wired in parallel might be worth an experiment?
Having just rebuilt my distributor and taking Ruby out for a run to the local A7OC meet it failed within five miles from leaving home. Replaced with yet another new one.