Ignition problem

[arcturus]

Originally Posted by Pigeon

Putting bosch condenser into UK Amazon brings up plenty of choices; I'd be surprised if the Portuguese site was any different. Doesn't matter if it's not the identical one.

When I do that I get a bunch of condenser tumble dryers
Addendum. found some on amazon .de. ordered two

[Underdrive]

I knew I had seen it somewhere, just checked Specifications in Haynes 120/1800 manual and condenser capacitance is 0.23-0.32 mF. Not sure if that would be any different for a 6v PV system though. Hope this helps. Also just consulted a very good reference book I would recommend to all, 'Haynes Automobile Electrical And Electronic Systems' which says 'A capacitor used in an ignition circuit has a capacitance of around 0.2 mF.

[simonvolvo]

Originally Posted by Ron Kwas

0.22uF?...I thought someone measured one once and it measured around 1.0uF...I don't have a C meter so I cant confirm...do you?...could you measure one and post...I'll see about getting access to a C-meter and measuring one also. It would seem that C value is important because it must play correctly with the L of Primary...

I had two lying around. I measured them and get 0.245 μF for the one and 0.285 μF for the other. (That is for a 12 volt system.)

Yes, the C must “play” with the L of the coil. The combination is supposed to give a short electromagnetic “ring” in the circuit when the points open, the frequency of the “ring” depending on the values of C and L. But I think the mere fact that the “ring” happens is more important than the actual frequency of the “ring”. It’s a bit like a bicycle bell: the pitch doesn’t really matter; as long as it rings and people can hear it.

I am sure 1.0 μF will also work.

[simonvolvo]

Originally Posted by arcturus

Problem solved, it was condenser again, not the usual warning hiccups before hand. I seem to need to change condensers more frequently than oil! I'm sick and tired of changing condensers, I think that I will change to a 123. as soon as funds allow.
Photo of points, note if possible the white rime on points edge, fortunately no pitting

I spy surface rust on the outside of your distributor body.

Are you sure there was good electrical continuity all the way from the condenser can to the car chassis, including between the condenser can and distributor body? Important, particularly if you run at 6 volts.

What made you conclude that the condenser was the problem? Could it not be that the act of swapping condensers serendipidously resulted in changing the electrical continuity from bad to good, and had nothing to do with the condenser itself?

[arcturus]

Originally Posted by simonvolvo

I spy surface rust on the outside of your distributor body.

Are you sure there was good electrical continuity all the way from the condenser can to the car chassis, including between the condenser can and distributor body? Important, particularly if you run at 6 volts.

What made you conclude that the condenser was the problem? Could it not be that the act of swapping condensers serendipidously resulted in changing the electrical continuity from bad to good, and had nothing to do with the condenser itself?

Had it been down to poor connectivity it wouldn't have happened instantaneously. Having had quite a few go belly up on on my cars I get to recognize the symptoms. But I do take your point.

[Ron Kwas]

underdrive & Simon; ...great info from both of you...I haven't measured one yet, but given your info, would certainly also expect a value in that range...regarding failure mechanism, the (Bosch) one I had fail had worked fine without issue before an extended lay-up of a car, then, after re-commissioning, failed when trying to rev engine...idled fine, but broke down and shorted intermittently killing the ignition when trying to drive...that was a tricky one to find...I suspect ingress of moisture during storage compromising the dielectric...

Simon; I understand the "ringing" of Primary L and C based on values and max expected RPM...I would expect value to be less dependent on V of system...but, given these Ign systems are somewhat different (different R and L?) from more typical ign systems with Ballast resistors, do you have any insight or thoughts on what the C-value would be for one of those ign systems?

Regarding corrosion on C connections on arcturus' vehicle...I hope with my constant preaching of "clean and tight connections, preferably treated with ACZP", his chassis connections didn't suffer from issues, but I do understand you had to ask...

Cheers

[Pigeon]

The ballast resistor systems, in the normal running condition (ie. with the resistor in circuit), look the same as a non-ballast system. The total series resistance of coil + resistor is about 3 ohms; the resistance of a non-ballast coil on its own is about 3 ohms. The inductance is the same for either coil. It does not, of course, make any difference whether the series resistance is all distributed or partly distributed and partly lumped. Therefore, both systems have equivalent L/R time constants, max currents, and energy storage; and both have the same requirement for the capacitor value, too.

[Laird Scooby]

Originally Posted by Ron Kwas

regarding failure mechanism, the (Bosch) one I had fail had worked fine without issue before an extended lay-up of a car, then, after re-commissioning, failed when trying to rev engine...idled fine, but broke down and shorted intermittently killing the ignition when trying to drive...that was a tricky one to find...I suspect ingress of moisture during storage compromising the dielectric...


Regarding corrosion on C connections on arcturus' vehicle...I hope with my constant preaching of "clean and tight connections, preferably treated with ACZP", his chassis connections didn't suffer from issues, but I do understand you had to ask...

Cheers

The thing i would suspect is simply age of the dielectric - a lot of these capacitors are made using metallised polypropylene and a re "cleared" as part of the test procedure which involves charging them with an extra high voltage before testing them for value and actual performance.

The clearing process can age the plastic so it fails prematurely although would still be out of its standard warranty following an extended lay-up. The capacitors are sealed with resin so shouldn't allow water ingress unless the resin is compromised or it was added on a damp day, sealing moisture in.

Good call on the clean and tight connections too!

I'm a bit late to this thread but having had a 144 about 30 years ago and suffered repeated condensor failure on that (duff components, proven on a digital Wayne Kerr bridge at work) it intrigued me. I think generally the standard of replacement parts has gone downhill largely due to things being made to a price, rather than a specification.

[Ron Kwas]

LS;

...good insight and info!...interesting, about the "clearing process"...I too have seen instances where the "test" process was so stressfull that it actually subtley (sp) compromised the product with "latent failures"...and this wasn't discovered until hard field failures started occurring later...investigations narrowed in on the test process as the root cause...a major ooops (expensive...recalls, etc.)!

I expect that bridge instrument to measure C value and so not necessarily show a high voltage breakdown mode of failure (unless it has a test mode for that also), but you might elaborate on the instrument, and mode of failure you found, further...

Cheers

[Laird Scooby]

Originally Posted by Ron Kwas

but you might elaborate on the instrument, and mode of failure you found, further...

Cheers

I might but it was late 1985/early 1986 - i've diagnosed countless faulty components (not just electronic and not just on cars either) since and the main reason i remember the digital Wayne Kerr Bridge is we had it in the training department ( i was an apprentice at the time) and although an older model (apprentices never got the new kit, it was always "hand me downs" from other departments within the plant) was the first digital one i'd seen or used.

As far as i remember it, the condensor had gone open circuit and i had 3 similar ones, all from the same shop and brand. I replaced it with a Lucas one and problem solved so presumably a bad batch.

As an aside, generally testing of any product can result in almost destructive testing and would certainly compromise some things out in the field. For example, something i learned about 25 years ago is when lifting equipment is tested to let's say, 500kg, they use twice that weight (1 tonne) and if it lifts and holds for a certain period of time, it's certificated safe for 500kg.

Obviously that's a different kind of testing and there are so many different methods of testing various products to ensure they work to try and list them all, or even research them all would take an incredible amount of time.