1992 Freightliner FLA / Cummins N14 starts, runs, then dies

Looking for some help with a 1992 Freightliner FLA cabover with a Cummins N14 Red Top.

Where it’s at now:
Right now, the truck will start and run, but only for about 30 seconds or so before it dies. Yesterday we actually had it running well enough to drive it around, but today it’s back to starting, running briefly, and then cutting out again.

A little background:
The truck ran fine the last time it was used in October. It sat through the winter with the batteries removed. When we first came back to it, it would crank fine but would not fire on its own unless we gave it a little ether. Once we got it going, it would run rough, stutter, and die. Over time we did get it running better, and at one point it would run longer each time we restarted it.

Earlier on, the RPM gauge was dead, and it was throwing blink code 121. We found broken wires near the speed/tach sensor plug, repaired that, and after that the RPM gauge started working again. After that repair, the blink code changed to 322.

What we’ve tried so far:

-Replaced and filled the fuel filter multiple times
-Charged the batteries multiple times
-Was cranking it in shorter sessions instead of just grinding on it
-Loosened the fuel cap to see if it changed anything
-Repaired the broken wiring at the engine speed/tach sensor
-Kept starting and running it as we were able

Current symptoms:

Starts and runs
Dies after roughly 30 seconds
Yesterday it ran long enough to drive around
Today it went right back to short run time and dying
Previously had white smoke while cranking
Previously had code 121, now showing 322

I’m trying not to assume too much or send myself in the wrong direction. I’d really appreciate any ideas on what you would check next, what questions you’d want answered, or what details I should look at more closely.

 

Thanks for the reply, I appreciate it. I’ve tried that some already, and if I give it a little ether when it starts to die, I can keep it alive for a while. I just don’t want to keep leaning on ether too much without actually fixing whatever is causing it to cut out in the first place.