Here are a couple thing to check.
This next test will tell us if the primary ignition system is supplying an electrical trigger pulse to the ignition coil. To test the ignition trigger pulse remove the small wires from the coil. Using a voltage multimeter connect the leads to both wires and set the multi meter to DC voltage. Next have a helper crank engine over and observe the voltmeter, if the meter jumps from 12 volts and then to zero in rapid succession the trigger system is working properly. Next check the ignition coil for corrosion if no corrosion exists use the voltage multimeter to test the coil primary and secondary circuits for continuity and resistance. This testing procedure will work for most automotive coils. With all wires disconnected from the coil, use a multimeter switched to ohms and check the resistance between the small side terminals of the coil. You should get a reading of 0.75 to 0.81 ohms of resistance. Then check the resistance between on either side terminal and the center high output terminal. The ohms reading should be about 10,000 to 11,000 ohms. Any significant deviation from these numbers would indicate the coil is shorted and needs to be replaced. If there is no primary ignition trigger output proceed to next step.
Step 7 - If the ignition coil has no trigger pulse input the primary ignition system has failed. This system contains a crankshaft position sensor (CKP), camshaft position sensor (CAS) which is a low voltage generating system (1.5 to 3.0 volts) and is then amplified to 12 volts by using a ignition module (amplifier) and then transferred to the primary side of the ignition coil. The ECM (engine control module) controls the engine ignition timing by advancing and retarding the primary trigger signal to the ignition module. You might say " if the crankshaft position sensor (CKP), camshaft position sensor (CAS) has failed wont it produce a diagnostic trouble code?" The answer is "not always" this is because some computer systems think the starter has failed or you have left the car in a drive gear or the clutch not depressed completely, not allowing the engine to crank over. In this case the computer just thinks the engine is not cranking over, even though it is. First turn the key to the on position, with the ignition coil connected to its wiring. Then, using a test light or a voltage multimeter ground one side of the test light or meter and test the coil terminals, there should be power on both sides of the coil. If the coil doesn't have power, locate the main computer system control relay and replace it with a new unit and re-test. If 12 volts is present continue to the next step.
Step 8 - Locate the crankshaft position sensor (CKP) and camshaft position sensor (CAS) (note: if your engine is designed with a distributor sometimes the CAS is inside the distributor housing) disconnect the wiring connector to probe the connector, there are three wires on most of these sensors so three tests are needed. Set your multimeter to ac voltage and probe any two wires on the sensor side, have a helper crank the engine over you should observe the multimeter jumping between 0 and 2.5 volts on two of the three combinations. Continue testing until three pairs of wires are complete. (I.E: right outer and center, left outer and center and right and left wires) if no pulse is present remove the sensor and observe inside the mounting port with a flash light. While looking inside the port have a help crank the engine over, you should see a small hole or magnet used to trigger the sensor, if this trigger is present replace the sensor. Perform this test for both sensors if equipped, if the sensors test ok suspect the ignition module (amplifier) or ECM.
Sunday, November 1st, 2009 AT 9:33 PM