ISX 15 Loosing Prime Overnight

A fuel line sucking air doesn't often show a visible leak. It's not under pressure

 

What I do, is bypass all the fuel lines from the tank, all the way to the pump, if possible.

If not, go to the nearest connection to the pump. I'll then install a line from the pump or nearest connection, and drop the other end into the fuel tank. Just take the fuel cap off the tank and put the hose in. If it tries to curl in the tank, attach the hose to a tire bar or winch bar with zip ties, then drop it in the tank.

Prime the system, get it running and let run for 20-30 minutes. Then shut it off and let it set.is this the one they put a starter on?

Did they have to move any fuel lines? Or remove a filter, or filter base?

 

It's losing prime. I'd be looking at fuel lines around the starter because that's when it started, and always the most likely spot of failure is in the general area where someone worked.

Maybe somebody has an ISX specific way to check it, but what I mentioned works.

 

When changing fuel filters at oil change (dry, not pre filled) and cycling the lift pump 4-5 times, it can take 30 seconds or more for the engine to catch with running the starter continuous. You wrote take maybe 2 minutes to clear up. With a known good system, the air will purge in less than 1/2 minute and idle will smooth out. After shut off with a 10 minute wait to check oil level the next start can still be hesitant and need a moment to clear air in the system. Try timing the actual time from ether start to smooth idling. (Is it really 2 minutes?)

 

Have you recently changed fuel filters…?
On my isx cummins I guess I got a bad filter once. Was ok for a few hours, but over night. You had to prime/ether it.