87 F250 6.9L Won't Start

[daum]

Just bought the truck for $1000, started when we got there, drove it home. Wouldn't start the next day, jumped it with the '79 and it fired up. Filled up front tank, drove around for a while and shut it off. Wouldn't start back up. Borrowed buddy's truck to take the wife and kid home and it fired up for him after I left. Drove it and left it running for about 10-12 hours that day, filled up rear tank. Got home that night, turned it off and tried to start it again and it wouldn't turn over.

Replaced the batteries with the ones from the '79. Fired right up, let it run for a while and then turned it off. Still won't start back up.

Going to replace the fuel filter this weekend along with getting new batteries so I can start the '79.

What else could it be?

Lights come on, engine cranks but won't catch. Then the lights go out after a couple of trys. This led me to replacing the batteries, which worked once.

[Mitchalvin]

Does it smoke when cranking? How fast does it spin? If it spins fast with lots of smoke it may be the glow plugs, if it cranks slow even with good batteries you may have a starter going out or bad cables. You may also have a fuel leak allowing it to lose prime overnight. This may be from the fuel water separator on the firewall, leaking caps on the injectors, leaking hard lines on the vehicle, or bad soft lines.