No start

[95suburb]

So the other day I was driving and parked the truck. Just cranked over for 30 secs then the battery died. I got a jump and the truck started immediately. Truck did the same thing today. Any Ideas? Volt meter is around 14 then suddenly drops to 10. Goes back and forth while I drive. The speedometer is also jumpy on cold starts. New glow plugs, relay, switch, batteries, all new power cables and grounds, lift pump, filter, ops switch and relay. Original alternator. Thanks in advanced.

......I looked under the truck and i have what looks to be a ground (looks like a big show lace) it is really beat up and goes from my frame to my flywheel cover. Could this be my issue?

[CAdiesel]

go ahead and replace the ground strap. they're cheap and very necessary. Some of the other guys could give the details on why but the fact of the matter is that if it ain't grounded right you are going to have problems.
Speedo runs off alternator so you might have alternator checked too. They'll do it for free at most parts stores.

[95suburb]

sounds good, thank you.