Q: Generally speaking, would a cracked crank shaft pulley be replaced during a full engine rebuild?

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We had our engine rebuilt and when we brought it home the mechanic said we needed to replace the crank shaft sensor. We did so and about a month and a half later the Jeep wouldn't start and idle. After testing found that cylinder 2 was dead and the rest had low compression. After this the computer ended up shorting out and then they blamed that on an "improperly seated crank shaft sensor". When we pulled the engine and all of that a part, we found the crank shaft pulley was cracked along the inside and that cylinder 2 was bright and sparkly silver color while the rest were all black. According to the shop that rebuilt the motor, this happened to the cylinder because gas was let in there from a faulty sensor. So I don't know if this is possible or true but my theory is much different.

My car has 209000 miles.
My car has an automatic transmission.

Hello there, this seems like a rather complex situation with everything that has happened. I will answer this the best I can with the information given. The crankshaft sensor could cause the vehicle to not start, but if it does, it would idle erratically. The ECU uses the information from the crankshaft and camshaft sensors to fire the proper cylinder and the proper time. The computer may become damaged if there is a short in the wiring such as with the crankshaft sensor. If a cylinder is not firing but the fuel injector is still spraying fuel into the cylinder, it can cause what we call a fuel wash. The fuel in this case is unburned and will clean the cylinder resulting in the clean cylinder you have noticed. Either the cracked crankshaft pulley or the crank sensor or the computer could of caused this misfire among other issues. It sounds like a few different issues contributed to the engine failing. With everything going on, you may want to have a professional inspect the car firsthand to verify what happened and advise on how to proceed in this situation.

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