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Tech501
Tech501, Auto Service Technician
Category: Car
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Experience:  38 years exp, ASE Mastertech with L1 Advanced Engine performance
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chevy cavalier: ran fine..injector..diff ecm - ignition coil pack

Customer Question

chevy cavalier 2.2 1990 bought car 3 days ago ttc selenoid bad disconnected and ran fine for the 3 days
would not start - no fuel out of injector-no spark at plugs-from junkyard got diff ecm - ignition coil pack-
still nothing adl reads code 12 any ideas or voltage checks or ideas? would crankcase sensor cause this ?
Submitted: 11 years ago.
Category: Car
Expert:  Tech501 replied 11 years ago.

 It has all the symptoms of a bad crank sensor



Crankshaft Position (CKP) Sensor


See Figure 1


A magnetic crankshaft sensor (Hall Effect switch) is used which is remotely mounted on the opposite side of the engine from the DIS/IC module. The sensor protrudes in to the engine block, within about 0.050 in. (1.27mm) of the crankshaft reluctor.


Click image to see an enlarged view
Fig. 1: View of the CKP sensor-to-crankshaft reluctor relationship



 


The reluctor is a special wheel cast into the crankshaft with seven slots machined into it, six of which are equally spaced 60° apart. A seventh slot is spaced 10° from one of the other slots and serves as a generator of a "sync-pulse". As the reluctor rotates as part of the crankshaft, the slots change the magnetic field of the sensor, creating an induced voltage pulse.


The CKP sensor, ICM or DIS ignition module sends reference signals to the computer control module (ECM/PCM), based on the Crankshaft Position (CKP) sensor pulses, which are used to determine crankshaft position and engine speed. Reference pulses to the computer control module occur at a rate of 1 per each 180° of crankshaft rotation for vehicles through 1993, or 7 per 360° of crankshaft rotation for 1994 vehicles. This signal is called the 2X or 7X reference because it occurs 2 or 7 times per crankshaft revolution, depending on the year of your vehicle.


For 1994 vehicles, the 7X reference signal is necessary for the PCM to determine when to activate the fuel injectors.


The computer control module (ECM/PCM) activates the fuel injectors, based on the recognition of every other reference pulse, beginning at a crankshaft position 120° after piston Top Dead Center (TDC). By comparing the time between the pulses, the DIS module or Ignition Control Module (ICM) can recognize the pulse representing the seventh slot (sync-pulse) which starts the calculation of ignition coil sequencing. The second crankshaft pulse following the sync-pulse signals the DIS module to fire the No. 2-5 ignition coil, the fourth crankshaft pulse signals the module to fire No. 3-6 ignition coil and the sixth crankshaft pulse signals the module to fire the No. 1-4 ignition coil.



Customer: replied 11 years ago.
Reply to Tech501's Post: Put new crank sensor in---- fixed!!!
Thanks !
Chris
Expert:  Tech501 replied 11 years ago.

Great, please click on the accept button to complete the transaction.

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