Q: Car parked for 1 month has dead battery

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After having to park my car for a month, it wouldn't start due to the dead battery. It is a 4 cylinder engine. After charging it, we found a vacuum leak. Fixed the leak, but after just 2 miles of driving, it lost power. My friend (who works in an auto repair shop) thought the ignition might be the problem, so he replaced it. Car still wouldn't start and only tests at 1 volt. Next, he took out the distributor, tested it and it works fine. Now, he thinks the problem might be the crank position sensor or the rpm speed sensor. But he doesn’t really know what the problem is. To continue - now the battery is fully charged and he says the problem isn’t the alternator, which he checked. When I asked him about the 1 volt reading, he said it was the crank position sensor/ rpm speed sensor. He has just about checked everything. My car had stalled when I came to a complete stop and that’s when it had lost power. This same thing happened also when the rotor button was bad on the distributor, but my friend also checked that and said that is good. Can you tell me what we should look for that will fix this problem?

The engine computer definitely needs to see engine RPM in order to power the coil. Between the ignition coils and the engine computer is an ignition coil power output stage unit which is supplied power from the engine computer. The power into this unit can be checked at the three pin connector at the unit. All 3 wires will measure battery voltage with the key on and the plug disconnected when measured with a voltmeter between the connector and ground.

A low voltage reading indicates a problem in either the engine computer or the wiring. While a battery voltage reading at the connector with a 1 volt reading at the coil indicates an issue in the ignition coil final stage unit or the wiring from the unit to the coil. You may want to enlist the help of a mechanic, such as one from YourMechanic, who will have equipment and expertise needed to diagnose the no start issue.

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