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The crank sensor can definitly cause the engine not to start, but it has to be diagnosed thru a factory level scan tool or automotive oscilliscope. So we can determine if it may be at fault, by testing some basics. You say you have "some" spark.
Is there intermitent spark on all cylinders?
Or is there only spark on 1 or 2 cylinders?
How are you testing for spark?
And how have you tested for fuel?
Was there a Check Engine Lamp illuminated, when it was running?
The unusual part of your description is that there is "weak spark." The CKP (crankshaft senor) only creates a signal for the computer to use to tell the module when to fire, and on what cylinder. It has no affect on the magnitude of the spark. The components that create spark are considered 'secondary ignition components.' These include, the plugs, wires, coils, and module. So if your getting spark on all the cylinders, this would entail that the computer must be recieving the CKP signal, and that somewhere between the module and the spark plug it's being lost. We need to get a better look at the spark, at the coil end. This is done with a generic automotive test lamp, do you have one of these? Before anything, make sure the battery cables are tight and clean. If they are not this will casue a voltage drop, and the ignition components may not get full voltage to operate, even if the engine cranks fine. Let me know if you have a test lamp, and i'll give you instructions on testing for spark strenght.
How about you can accept when we've gotten as far as we can?
#1, I'd like to show you haw to use the test lamp to check for the strenght of spark, this way I can get an idea if it truly is a spark issue or do we have too much fuel, putting the spark out. Clamp your test lamp to good engine ground, near the coil pack area. If this model has the coil packs under the intake, it'll be difficult to do the test, unless you can get the car up on jack stands. Pull one coil wire off, and keep the tip of the test lamp approx 1/2 inch away from the coil tower. Have an assistant crank. Will the spark jump to the tip? If so what color is it - orangeish or blue? Do the rest of the coil towers, one buy one, replacing the respective wire on the previous one as you go, so that you will not get shocked. If the spark does not jump 1/2", move the tip of the test lamp closer and closer until you can see where it arcs to the tip. And let me know your results. Also, did the exhaust ever get red hot??
If the exhaust got red hot, this concerns me. It either means that the ignition timming (computer controled) is excessivly retarded, or the cam timming has changed (timming chain). Or it could mean that too much fuel is entering the intake. Are you sure you don't have any more codes in the computer? Do you know how to check for codes? If you still have a knock sensor code - this may mean something. I want you to still check the spark strenght, but just so you know, we're going to have to make a few more checks before comming to a determination.
How many miles are on this car?