Variation on "Start you blighter!" - solved

[Rickoz59herald]

Variation on the theme...

Dad gave me his 59 Herald recently, as he now can't get in and out of such a small car. It's had a few issues which I was working through. Rear wheel bearing, a bad habit of blowing head gaskets, seals on the convertible hood not staying put... I've been driving it to and from work over winter (on sunny-ish days) but eventually it became very hard to start then eventually it refused to start. Plenty of fuel - no spark. Poor spark out of the HT coil lead. Ok, either the coil or condenser has died. Replaced the condenser with a NOS one. Hot spark from the HT lead - great! Nothing at the plugs - not so great.
Hmmm - only thing left is the distributor cap. Put a multimeter across the coil lead connector and the carbon brush - open circuit. There should be some resistance....

Carefully removed the brush and its spring as I didn’t want to stretch or damage it. The spring looked burnt, and the hole it sat in was black. After a squirt of WD40 in the hole and cleaning it out with a cotton bud I could see the metal the spring sat against. Cleaned the spring and brush and pushed it back. I used a flat punch to carefully push the brush until it actually clicked in place against the metal. I checked for continuity with the multimeter and I had a reading! I turned it over with all plug leads off and one aimed at No. 4 plug. Damn thing tried to start!

Put it all back together and away she roared – well, as much as a 948cc engine can roar. It actually feels like I’ve gained a couple of HP. 

Moral of the story - when you have eliminated the obvious, whatever remains, however improbable, must be the problem. I guess the spark from the HT lead had to jump the gap to the brush spring and eventually created an insulator. I’ve had a brush spring break and a carbon brush crumble, but this was something new. Dad’s 82 and been mucking around with cars for most of that time and never had that problem. Live and learn... 

Cheers

Rick

[JohnD]

Welcome, Rick!  You and your Dad have good taste!

AND, good practice - your diagnostic procedure is exemplary, and successful, of course!  Well done!

I'll look forward to hearing more of your Herald.  As a semi-daily user, you're in the elite group already!

John

[Rickoz59herald]

Thanks John

Normally I'd just swap caps, but my spares are 300 miles away and nobody local had one that I could borrow. I wasn't going to buy a new one if it was a simple issue. 

I have a 3 mile drive to work, and on a day like today why would you drive a modern car?