2004 Sprinter cranks but rarely fires.

I'm looking at a 2004 Shorty low top Sprinter with 331K original miles. It's a one owner vehicle and, when used, the maintenance was kept up. The body's good. It's dirty from sitting unused for the last 1.5 years. He's asking $1500 for it...
The problem is, it will crank and crank and rarely fire up. It does sometimes but most of the time it cranks until the battery is dead. When it runs it runs well and there are no dash check lights on. It does have some "black death" going on but it's not real bad.
I'm handy with cars but don't know much about Sprinters or diesels. Can someone point me to where to look to see what's going on?
The problem is, it will crank and crank and rarely fire up. It does sometimes but most of the time it cranks until the battery is dead. When it runs it runs well and there are no dash check lights on. It does have some "black death" going on but it's not real bad.
I'm handy with cars but don't know much about Sprinters or diesels. Can someone point me to where to look to see what's going on?
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