Tip & How-To about Chevrolet 2500
Either you are not getting spark or not getting fuel. A bad crankshaft
position sensor would cause no spark at all. You can pull one spark
plug, place it back on the plug wire. Lay the plug electrode next to a
metal surface. Have someone else crank over the engine while you observe
for spark. You should see a spark jump from plug to the metal surface.
(plug electrode should be no more than 1/4" away) If you don't have
spark, put the plug back in and move on to the next plug and try that
one. (the correct way is to use a spark tester) If you have no spark in
any plug, you may want to test the crankshaft position sensor with an
ohmmeter. You can also use a meter to test power at the ignition module.
If you find that you do have spark in every plug, then it's possible that you don't have fuel. There is a fuel pressure test port on the fuel rail. There is a cap and a valve. With the key in ON position ,you can place rag over the test port, press in on the valve and there should be fuel that comes out meaning there is fuel pressure. (the correct way is to use a fuel pressure gauge if you have one)
If you find there is no fuel pressure, turn the key off and back on again. You should hear the fuel pump. If you can hear the fuel pump, then it is working. That means you may have a plugged fuel filter or faulty fuel pressure regulator. If you do not have hear the fuel pump, check the fuse and fuel pump relay. You can test the relay and a fuse with an ohmmeter on the ohm setting. You can also use a voltmeter and check power to the relay and also to the fuel pump to test for 12 volts. If you have power to the pump but the pump is not running, it is likely faulty. If you don't have power to the pump, then either the relay or fuse is bad. If they test out ok, then test power from ECM.
These are the most common causes of a no start. If you have any bad sensors of any sort, it would likely set of the check engine light. Then the computer should be tested for engine codes which can be done with a scan-tool.
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