1993 Astro won't start under 14 volts

How old is your battery? And is it a sealed or unserviceable unit with the green eye? I had an experience similar to this with a factory GM battery. The eye was green and checking the voltage was fine however an internal wall to a cell had failed somehow and battery performance was lost. Borrow a new battery from someone. Unplug your battery for about one hour to let your computor system reset. If your problem persists, then the alternator will be the next logical step to find a break or short in your system. This will be internal, therefore replacement with a rebuilt or new one will be called for. How old is your alternator, do the wires leading to it appear chaffed/frayed?

Change the battery out I had the same thing go wrong with my pickup

Try checking for corrosion inside the main battery terminals. Especially on a side-terminal battery they tend to get corroded beyond the post.

Soaking them in hot water for a minute or so. Drying thoroughly and then cleaning up with some emery cloth is the best way.

You'd be suprided at how much voltage drop a small amount of corrosion can cause.

The battery has been tested four times. The first three times it tested alright. Yesterday it failed, having only 10.3 volts after 2 load tests. I thought great, at least we found it. Ha! Hooked up the new battery, does the same thing. I have checked all the wiring and cleaned the connections to be sure they were making good contact with each other. All the hoses have been checked. The alternator is brand new. I had thought that was the original problem and had it tested. It was on the border line and had a bearing that was starting to make some noise, so I replaced it. The starter was checked and it is well within it's parameters. The coil and ignition module have also been changed. Something is drawing a large amount of power during startup and while operating. The system voltage while running is between 15 and 16 volts, a lot higher then the normal 14 that it usually is at running. I am beginning to suspect the fuel pump. The pump doesn't make any more noise then usual, and it doesn't surge, miss, or stall while running, and it does come up to pressure right away. But it just seems strange that I am getting a good hard spark and it is spinning really good, yet it won't fire without the extra voltage. I did just replace the pump about 15 months ago, but that doesn't really mean much. The thing that leads me to believe this, is that when this problem first started, I could turn on the ignition severals times to pressurize and then I would get lucky and it would fire and run. But through testing it, everything appears to be well within it's parameters with the pump. I don't know. Hate to tear that tank out and found out that isn't it.

FIXED! Yeah!

Turned out that the fuel pump was not coming up to pressure unless it had at least 14 volts. At 12 volts it would only give 48 pounds of pressure. I install a new fuel pump and turned the key and it fired right off without any help. Thanks for everyone's help and suggestions.