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Crankshaft Sensors
What I'm going to talk about today are crankshaft sensors. If you remember on the older cars you had a distributor. If you look at a modern car you'd be hard pressed if you could find a distributor. This is one of the key components that are in distributor-less ignition systems that are replacing distributors. The crankshaft sensor sticks into a hole in the engine block and when it's in the engine block you can only see the head of it where a wiring plug plugs into it. The rest of the sensor is inside the engine.
This sensor picks up on a series of notches on the crankshaft so that the computer running the spark and the fuel injector on your engine can figure out where cylinder number one is and if in fact the engine is actually cranking over and the speed that it is turning over at. This sensor is a very important input on a modern car. This one is one that was recently replaced on a car that was towed in.
When the car was hot, there would be no spark and it wouldn't start and when it cooled down there would be spark and it would start again and then you could drive for 5 or 10 minutes. This is typical symptom of a car with a bad crankshaft sensor. Another symptom that you could have is a vehicle that would work fine one night and you can drive home with no problem, you come out the next morning the car is cooled down, you turn the key, no spark, no start and then you would have to get it towed in to get it fixed. It's not at all uncommon to replace the crank sensor in a GM V6 engine, but it usually has to be at least a few model years old and have a lot of miles on it before it fails the first time. But that isn't always the case on a crank sensor failure.
For example on late model Grand Cherokee's and Ram pickups: the crank sensor can fail at a fairly early age. And in many cases there are no symptoms leading up to it. You're driving alone, everything is fine and then all of a sudden it just cuts out and you're dead in the water, you have no start, no spark situation. The engine cranks over but it won't start. The crank sensor is usually not easy to locate and it's not easy to diagnose either. It usually involves a tow in and you'll have to have a professional mechanic check it out and then replace it. On the GM V6 this sensor for example is only a $40 part: rather inexpensive. Other engines could be $100 or more. It's certainly not something that a do-it-yourselfer can do; you're going to have to get it checked out by a professional mechanic.
Till next time, I'm Bill Gardiner for Motoring.
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