[DK on the road]

John, last year I had a similar experience while driving into Twin Falls ID. It ran at fast Idle, or rolling down the road at speed, but below 800 RPM it struggled and eventually shut down. My Bowl was empty after sitting or it shut down. It was hard to restart, due to loosing prime.
I spent a lot of time looking for glittering Unicorns before getting back to basics and getting logical on fuel supply. I thought my lift pump had failed, I was testing pump pressure, repriming filters, etc. it wasn't getting consistent fuel.

I Pressurize my fuel tank with 3-5 psi to a open line before fuel filter. I had a loose fitting above my fuel tank that allowed enough air at low speed and not enough fuel to keep it running. After shutting down, the pickup line would slowly lose suction and prime. The air pressure showed bubbles at the fitting, and I heard the PSSS.
Simple fix, but I spent 6 hrs trying to figure it out. But that's me.

Hope it's this simple.

[ccjohnson]

Possibly an air pocket in fuel line run. If so, the air pocket collects in the high spots of the fuel line run. I had to pressurize my tank and bleed about a gallon of fuel out at primary filter on engine to fix mine when I got air in the fuel line. You will still need to figure out how air got in the lines if that is the problem. I had opened drain cock on my fuel / water separator while Detroit was running to get fuel to prime generator fuel filter. I WILL NEVER do that again!

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Changed fuel filter, after draining water - bottom valve. after no start went and bought quart of diesel and poured into top of bowl. started after a bit ran rough. bubbles pouring into sight glass but it kept running. decided to continue trip. 250 miles later with no incident bowl was clear and engine now will slow idle without stalling. The manual shows the high level when to change the filter. as some of you suggested I change the filter even though it was not even half way up. Lesson is
dont wait until its high in bowl like the manual would suggest.

[arcticdude]

As an alternative to getting diesel, you can use automatic transmission fluid instead. Cleaner and easier to pour.

Sounds strange I know, but it works.

[Wardworks]

I was 99% sure it was the filter. Mine did the exact same thing. Even though the site glass said it was not due to be changed yet, it was. Glad it worked out for you!