I've got an '89 and occasionally, I will try to start the car to find the battery is as dead as a doornail. Maybe someone out there can help.

When I go to start, nothing happens, no lights, radio, starter, nothing. When I put the battery on a charger, I heard what sounded like a fan spinning inside or under the engine. I started pulling fuses to determine what it was. When I pulled the fuse for the fuel pump, it stopped. What I determined is (for some reason), the relay for the fuel pump doesnt shut off when the engine is turned off and it runs the battery dead. Has anyone else experienced this? If so, is the problem as simple as replacing the relay? Besides being annoying to have your battery randomly go dead on you, I dont want to lose a fuel pump because it was running all night into an engine that wasnt accepting fuel.

 

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http://forums.corvetteforum.com/show...=battery+drain

See if you find an answer in these. Troublshoot

 

Is it the blower fan you are hearing? The relay is notorious for going out which causes the blower fan to stay on even with the key removed. To check the relay, Pull the connector with the big red wire off the triangular piece on top of the blower fan ( on the firewall, passenger side), and see if the blower turns off. A new relay from a Chevy dealer will cost $547. From GM parts direct - $274. Discount auto parts - $103.

 

The fuel pump running after shutdown will run down a battery and it could be as simple as a pump relay with contacts stuck together and repaired by relay replacement. First I would make some measurements to see if the relay is really defective or something else that is keeping the relay coil energized during ignition off. First, the fuel pump relay coil is supplied 12v from the ECM and the ECM only turns on the fuel pump for 2 seconds when you attempt a crank and if the engine starts, an oil pressure switch supplies 12v directly to the fuel pump when oil pressure exceeds 4 psi. If your fuel pump runs with the ign off, pull the relay and see if the pump stops. If it does, either the relay is defective, or the ECM is defective. You can use an ohmeter to measure if the relay contacts are open circuit (between terminal A and E). If open, then the ECM is defective. If the pump does not stop with the relay unplugged, then you may have a defective oil pressure switch and you can unplug the oil pressure switch and with the engine off, use an ohmeter to find out if the oil pressure switch is open circuit (it should be) or if it is closed, and if closed, the switch is defective.