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The exact procedures for correctly diagnosing ignition related problems on DIS equipped vehicles vary from manufacturer to manufacturer, and sometimes can be quite lengthy. But, here are some tips to help solve your ignition-related problems. There are several scenarios that could arise at your counter, yet the following tips could benefit you, your store (increased part sales) and your customers (replacing the right part, the first time):
- The result of your DIS Tester's module test is the first important step
- Has the customer checked the on-board computer for stored trouble codes? (a Code Reader can be used)
- Gather as much information about the customer's vehicle and conditions surrounding their complaint (i.e., recent repairs or accessories installed in their vehicle, etc…). You can download a quick check list form from the UPGRADES/DOWNLOADS section in this web site.
- When, where and how does this problem occur?
- How long has this condition existed for?
- How often does this condition occur?
- Always double-check the obvious (i.e., thorough visual inspection- blown fuses, unplugged connectors, etc )
Did the module pass or fail?
MODULE PASSED:
If the module passed the test, you need to ask your customer some questions.
- Did you check for spark at the spark plug with an approved spark tester?
- A timing light can be used also to determine if there is spark (checking for spark by pulling a plug wire off a plug is not recommended and can damage an ignition coil and/or module).
NO SPARK CONDITION:
If the customer does not have spark, you should first ask them whether there has been any repairs done that might have routed the wiring out of the original location. Many times a wiring harness has been routed too close to the high voltage plug wires which disrupts the signal causing intermittent problems. It is very important that all the wiring harnesses be returned to their original locations insuring that all systems are operating properly before any diagnosis can be made. Once this has been confirmed these simple tests should be performed.
- First, your customer will need a repair manual to help them identify the correct wires for the following tests, an automotive DVOM for the voltage measurements and an approved test light will be required.
The DIS system has five major circuits that must be checked, battery (B+) voltage, ground (low reference), crankshaft sensor (CKP+), EST/SPOUT (electronic spark timing/spark output timing) and tach signal (reference/PIP). In order for the ignition module to supply voltage to the ignition coil(s), the module must also be supplied with "fused" battery voltage. In turn, to complete the circuit to the battery, the ground to the module must be intact.
This test will verify the integrity of the battery voltage and ground circuit. With the module harness connector removed from the ignition module, place the positive DVOM probe into the power supply pin in the connector and the negative DVOM probe into the ground pin in the connector. While the key is in the "on" position, you should read battery voltage on your DVOM.
If there is no voltage, remove the negative DVOM probe from the connector and place it on the negative battery terminal. If there still is no voltage, you need to check the fuse or wiring for the power supply circuit. If you now see battery voltage with the negative DVOM on the negative battery terminal, the problem is in the module's ground wire circuit.
TECH TIP: Some systems utilize the module case for the ground circuit. To check this type of module's ground, attach the positive DVOM probe to the module case, and the negative DVOM probe to the engine block. Using the voltmeter function, crank the engine and read the voltage. If the voltage is more then 200 millivolts (.2 volts) then the ground connection for the module needs to be inspected. Check the nuts or bolts that secure the module to its bracket for tightness.
- If no problem is found with the power or ground circuits, the next circuit to check is the crankshaft sensor. First, you need to determine if the vehicle's crankshaft sensor is a Hall Effect or a Magnetic type. (consult the specific vehicle service manual for exact procedures)
If the vehicle is equipped with a Hall Effect sensor, locate the signal (CKP+) wire pin in the module's harness connector and place the positive DVOM probe here and the negative DVOM probe to the engine block. Select the Hz (hertz) function, now crank the engine, you should read approximately 10 to 1000 Hz depending on what type of vehicle you are testing. If there is no reading, the crankshaft sensor will need to be replaced (remember when replacing the crankshaft sensor on some models the clearance between the interrupter rings and sensor are critical, make sure none of the rings are bent before you replace the sensor).
If the vehicle is equipped with a Magnetic (variable reluctance) sensor, locate the signal (CKP+) wire pin in the module's harness connector and place the positive DVOM probe here and the negative DVOM probe to the engine block. Select the DC voltage function, now crank the engine, you should read approximately .2 to .4 volts. If there is no reading, the crankshaft sensor will need to be replaced. If any one of these tests failed, you will need to repair the wiring or sensor accordingly and retest.
TECH TIP: Always double-check the wiring and connectors for opens or shorts and verify the voltage and ground supply to the sensor before replacing the component (consult the specific vehicle service manual for exact procedures)
- If all these tests are good, the ignition coil(s) will need to be checked next.
This quick test can be used on GM systems to verify if the module is working and to pinpoint if there is an ignition coil(s) problem. This test must be performed with an approved test light. First, remove the ignition coil(s) and connect the test light across the module's terminals, now crank the engine. If the test light flashes, the module is good and the ignition coil(s) need to be replaced. For Ford vehicles, this test requires the ignition coil connector to be removed and the test light connected between the battery voltage terminal and the coil trigger pins one at a time. Whenever an ignition coil(s) fails, most manufacturers recommend replacing the spark plugs, plug wires and coil(s) at the same time.
SPARK PRESENT, BUT WILL NOT START:
If the customer has spark, it might be necessary to check the Crankshaft or Camshaft (CKP or CMP) sensor circuit for opens or shorts because some systems require this signal for the computer to synchronize fuel delivery. Although the engine has spark and fuel pressure, it will not start.
A quick test here is to install an approved "noid" test light to an injector harness and crank the engine. If there is a no flash condition, the fuel injectors are not being pulsed. Since there are many different systems and several different fuel injector-synchronizing methods used, you should consult the service manual for exact details for your system. If the fuel injector is being pulsed, you might direct them to check for a fuel pressure or other fuel related problem. Further testing might require a fuel injection pressure tester.
MODULE FAILED:
If the DIS module failed the test, it is important to note what area of the module has failed. Because the ignition module failure might have damaged other ignition-related components, or the module was damaged due to failed ignition related component. Either way, it's critical to inspect the system before installing new parts. The following chart will assist you in affected areas to thoroughly inspect before installing the new ignition module:
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DIS Test Failed
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Component Area Effected
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Break Current/Current Limit
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Ignition Coil(s)
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Firing Order
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PCV Valve, Air Cleaner Housing and Duct, Mass Air Flow (MAF) Sensor, Manifold Absolute Pressure (MAP) Sensor
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GM L.P. Circuit
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Ignition Coil(s)
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Start Retard Control
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Perform Starter Battery Test
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Dwell Time
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Ignition Coil(s)
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As a general rule, most manufacturers recommend the replacement of the ignition coil(s), plug wires and spark plugs whenever an ignition coil has failed. Most importantly, if you are reusing any component, you must thoroughly inspect and test each component to the manufacturers specifications for the year, make and model of vehicle you are testing.
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