Q: Car parked for 1 month has dead battery

asked by on July 22, 2016

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.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Transmission fluid is leaking

I would not recommend driving your truck under these conditions to prevent transmission damage. My first recommendation would be to have your transmission system inspected by an automotive service professional to locate the source of the leak. Possible leak sources...

Car cranking, but not staying on

If a car cranks and doesn't start, I would typically check the spark and fuel, either of which could be the cause of your problem. If everything tests out ok and the truck still doesn't start, then I would suspect...

Key not turning the ignition cylinder.

Hi. A test that can be administered would be if you have a spare key, try to turn on the car with that key. If it turns on, then that would indicate you have a bad key and you should...

Related articles

How Long Do Brake Rotors Last?
Brake rotors, sometimes called discs, are an important component of the braking system on any vehicle. The brake rotors are the part of...
How Air Bags Work
Designed Designed to protect the occupants of a vehicle in the case of an accident, air bags inflate when the vehicle collides with another object, or otherwise suffers a sudden deceleration. Absorbing the energy of the impact, vehicle owners need...
How to Replace a Coolant Vacuum Valve Switch
A vacuum line attaches to the vacuum switch in your car as part of the engine’s heating and cooling system. A faulty switch can break your heater.