Monday, December 11, 2006

No spark for 1992 Olds ninety Eight with 3.8L engine: No Codes


My car quit on me yesterday and following ATS course, I found it has no spark. As per your lesson, this problem is caused by crank sensor and ignition module. I first replaced the crank sensor and found still no spark. Went and got a new ignition module and same thing happened. But after spending all these money for parts, I still have no spark? What am I doing wrong? Is my engine computer buggered up too?

ATS Adviser:

First of all, although ATS fixes tells you to suspect both crank sensor and ignition module, there are a few tests involved before replacing those parts. Examples:

Did you check if the crank sensor has proper ground and power supplies? If you requested the ignition wiring diagram, you can see the ground and power supply wires. Always go to the basic: Ground wires should read 0.250 volt or less with key on engine off. Power wires always give you around 12 volts with key on engine off.

These simple tests will tell you if there is a problem with the sensor or ignition coil. The same is true if the wirings connected to them. Those parts might be OK but if the wires are shorted because the insulation is bare, your new parts will not work still.

Finally, a lot of local parts stores can test those parts for you and they can tell if the parts are OK or not. If they say the parts are tested OK, then it gives you a red flag to test the wires or the ecm (engine computer). Again to test the ecm, all you do is test what? The ground and power supply readings at the terminal of the ecm with key on engine off PLUS, the reference voltages. This is the most basic tests of ATS troubleshooting and if you use this method, you will solve about 90% to 95% of engine electronics problem.

ATS Tip:

When testing your wires, use wiggle tests and wiring diagram to trace the shorted wire.


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