Sep 03, 2024
Time for the new puzzler.
Here it is.
This happened years ago in the shop.
A customer came in with a car that wouldn't run. He said he went to start it that morning, turned the key and it cranked, but it would not start.
I asked him if he opened the hood to take a look.
The customer said he did not. He just immediately called a tow truck and that the car should be pulling in the garage any minute.
So, the tow truck brings the car in. And we get inside the car and turn the key, and it sounds pretty good.
It sounds like there's compression in the cylinders, and we smelled gasoline even. But we open the hood and find out that the distributor cap is broken into a million pieces, smashed to smithereens.
I was able to get most of the pieces, but some of them were still stuck to the wires. So the distributor cap has a piece stuck to one wire and a piece stuck to another wire. The spark plug wires are still attached to it for the most part, but it is broken beyond recognition.
And I said, "Well, maybe there was a crack in the cap, or some such thing? Maybe the rotor hit it? Maybe there's something wrong with the rotor. The rotor spun around and it broke the thing maybe?"
Those are all very unlikely things, but all slightly possible.
In any event, we put a new cap and rotor on this thing.
The car starts right up and runs great. We park it outside and run it a bit, drive it around, to make sure everything is okay now. And it is.
The end of the day, the customer comes to get his car. He pays the bill and then leaves.
About 5 minutes later, he comes back, all upset and says, "What is this? Some kind of joke?"
I go out, open the hood, and the distributor cap is again smashed into a million pieces.
And the puzzler quesiton is, what was happening here?
And a hint, this would happen much more often with cars of yesteryear. And these days, this wouldn't happen at all, because most cars these days don't have distributors, distributor caps and rotors.
So, what was happening to this guy's car?
Good luck.
So, what was happening to this guy's car?
And the hint, this is only something that would happen with very old cars. Would not happen now.
And the answer is...
This would not happen in new cars because they are missing one piece that older cars used to have. And this is the vacuum advance.
The vacuum advance was simply a vacuum operated device, which contained a diaphragm and a rod, and when the engine vacuum was high, it would pull the plate and advance the timing. It was an elegant little device.
This is all done electronically now.
And in this case, the vacuum advance of this car had a little hole in it. And the vacuum is pulling from the manifold. And what's in the manifold is a mixture of gasoline and air.
When the thing was shut off, this mixture would waft into the vacuum advance, penetrate the diaphragm, and get on the other side of the diaphragm, where it would get into the area of the cap and the rotor, where there are sparks of high voltage.
And when that mixture of gasoline and air was in there, and then he turned the key, that first spark that was made exploded the cap.
All from a little hole in the distributor cap.
