The Strange Ignition Mystery - solved

[Ricky Luke]

This actually happened to my dad's 59 Triumph Herald convertible, but I thought I'd post here because it was an unusual problem.

 

Dad gave me the Herald recently, as he now cant in and out of such a small sports car. It's had issues which I was working through. I've been driving it to and from work over winter (on sunny-ish days) but eventually it became very hard to start then 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 in the distributor with a NOS one. Hot spark from the HT lead, nothing at the plugs.

 

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. 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’ve had a brush spring break and a 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. 

 

Rick

 

 

[Dave72dt]

Some problems really don't show up very often and tracking them down can be very frustrating.  I once had a rotor ground to the distributor shaft.  Black rotor with a very small dot of gray under the center terminal contact point and even smaller gray dot on the bottom side of the rotor.  The rest of the rotor looked like new.  That's why I've always recommended a systematic approach to troubleshooting.