A DEAD VOLVO (hehe!)

A friend of mine once called on a friday afternoon (Dont they always?) She was moving to another house that weekend and her eightysomething Volvo 240 had suddenly died, towing the third trailerload of furniture. Arriving at the scene I noticed that someone had made a mess of the underbonnet HT wiring loom. A couple of guys (All guys are mechanics, right?), including her boyfriend had heroicly tried to make the Volvo start. No such luck. Dont you just hate it when someone incompetent tries to fix something, and then calls you?

I took one look at the points (the distributor cap was hanging loose at the other end of the engine) and said "-No wonder it wont start, with a dwell angle setting like that". Not knowing whether (but suspecting that) the aforementioned braintrust had fettled the points, I adjusted them by eyesight so that they at least closed between each lobe-pass-by. Then I started assembling the rest of the ignition system, putting back the odd undone spark plug and such.

Before I refitted the distributor cap, I adjusted the dwell angle to 50 degrees (Yes, I do carry a test-meter in my boot). Then we tried to start the damned thing. STONE DEAD. Rechecking every connection was fruitless, so I started investigating the ignition system step by step.

The coil did get power, although an unhealthy 7,2 V and there was no start-up by-pass of the ballast resistor. (Funny though, Volvo is Scandinavian) It also provided a spark from it's output lead to the block. (Things were looking up...) But when fully assembled, there were no detectable impulse on any HT lead for my strobe-light ignition timer. Shorting the ballast resistor made no difference either.

Hmmm... I carefully examined the king lead from the coil, and the distributor cap again. A bit worn but no obvious faults. The rotor looked fine(ish) too, but that funny section between the two ends of lead material puzzled me. Most rotors have a solid lead of some metal-sort, this one was obviously a radio-noise-suppression rotor.
A quick test with the ohm-meter showed that there was contact through it, albeit some resistance. 50 Kohm to be precise! Not knowing whether this read-out was normal for a suppression rotor, I just stood there studying the rotor, thinking "-where the heck do I find another one at these hours to test?" whilst the others were watching.

Then I got an idea. Component sharing has been an important word in the motor industry for decades. Parts availability and cost, is the upshot. Volvo is Swedish and uses Bosch components. Saab is Swedish and uses Bosch components. I opened the bonnet on my Saab, took out the rotor and without even looking at it, fitted it to the Volvo. The others were now looking at me in disbelief. "-Start!", I ordered, and the unhappy car owner twisted the key. The engine started instantly! I didn't let them have my rotor of course, but now they knew what was wrong.

I would estimate that 90% of all roadside breakdowns are due to ignition failure of some kind, but I've never seen a ROTOR fail like this before...