Vehicular Drama

The biggest risk in this trip isn't the fuel I'm using, it's the 24-year old car I'm driving. That fact has been made clear to me this week. The car isn't starting.

I drove it to work on Wednesday. When I hopped in to go home, it would not start, and I killed the battery trying. So, I took the battery out and hitched a ride home with a coworker. Thursday morning, with a fresh charge on the battery, I try again, and again kill the battery trying to start the car. With a little help from my friends, I wheeled the car over to a power outlet and plugged the block heater in.

Current situation:
The car is in a parking lot, with the block heater and battery charger plugged in. It hasn't moved for almost 4 days now.

Possible problems:
Dead battery: I took the battery to the auto parts store to check it's health - the guy charged the battery and says the battery is in great shape. Car still won't start.

Gelled fuel: (diesel fuel solidifies at low temperatures: it's been as low as -6F at night) I added some anti-gel to the tank. Car still won't start. If this is the real problem, I probably will just have to wait until it reaches a balmy 40F on Tuesday.

Bad glow plugs: I noticed this: when I try to start the car, on the first attempt, the glow plug indicator light does not light up, but if I immediately try again, it does light up - does this indicate a problem with the plugs? I hope so - that would be an easy fix. I purchased 5 new glow plugs (~$50), and will investigate this weekend.

Bad glow plug relay: I really hope it's not this. New relays cost ~$150 and have to be special ordered. When I investigate the plugs, I'll also be able to see if the problem is the relay.

Could there be something else I haven't considered? The starter seems to be working fine - the engine is turning over smoothly. When I turn the key, I hear a nice solid thunk of relays operating. Any ideas out there?

I will have more info after I've had a chance to look at the glow plugs.