Won't stay running, dies, starts hard, dies again

[Mammoth73]

My 7.3idi factory turbo won't stay running. It started the other day with a hard start, then died twice going to work. Showed the exact symptoms of running out of fuel except I had fuel. Did the return lines twice, replaced pickup tube and blew lines as well as cleaned the tank of debris. It'll start hard, run for about a minute then sputter out. Bleeding the Schrader valve of air gets it started again but then dies right after. Towards the end the shader valve wasn't putting out anything when cranking, no air built up, no fuel, I'm thinking the check valve maybe? But the thing is the valve seemed to be working fine when the problem started and up until Just before the point when I gave up. I ordered a facet duralift pump but my truck is stranded on the ranch at the moment. Any input is appreciated, I'm usually able to figure this stuff out but this really has me stumped [emoji35]

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[DrCharles]

Sounds like a combination of air intrusion and a bad lift pump?

The Facet pump should cover-up the first problem and fix the second.
You DID check the fuel filter, right? Doubt it'd be plugged solid but never say never.

 

[BrianX128]

Check your oil for diesel if your lift pump did end up dying. See my 60 some post nightmare I went on with fuel in the oil. Almost had my engine runaway in my driveway.

 

[Mammoth73]

I've changed the fuel filter twice now, once right after I got the truck, then again after I cleaned the rear tank and blew the lines just for reassurance. How would I tell if there's diesel in the oil? It usually seems good, done 2 oil changes with Amsoil/delo been adding a quart roughly every 700-1000 miles

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[Mammoth73]

I should add that I've had the truck a little over a year now. Got her at 240 and she's now at 256

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[IDIBRONCO]

Your oil will be thinner, run off of the dipstick more like water, and will smell like diesel. Your oill level will also rise. There's probably more, but these are what I could think of right off of the top of my head.

 

[Mammoth73]

Update - I just finished installing the facet duralift pump and while it seems to work flawlessly, it'll prime and prime and I'll keep letting air out of the Schrader valve, but it seems as if it's sucking air as fast as I'm bleeding it.
Running just the pump gets bubbly fuel leaking from the bottoms of few of the caps that I've replaced twice now. Cracking the injectors and cranking gets fuel to them but as soon as I close them and try to start it'll run then dies after a few seconds.
I'm about ready to push this truck off a cliff with all these fuel problems. I'm gonna try and put the main draw from the electric pump into a 5 gal jug of diesel and see if it exhibits the same symptoms. Hopefully this should help to isolate the leak to either the engine bay or the tanks and lines. I'll let y'all know what I find

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[DrCharles]

If the electric pump is sucking air constantly, then the problem is upstream of the pump. That can only be tanks/pickups, selector valve, or lines.

You have to get air-free fuel from the Schrader valve with the pump on or it'll never start and run properly...

 

[Mammoth73]

Ya it runs fine off the jug, but don't see any leaks along the entire length fuel lines going into either tanks.
There's some deeply oil coated spots where the line runs under the flywheel. But other than that I can try and prime the line coming from the tanks into the pump, but it just keeps going down with no visible fuel leaking anywhere up until the selector valve other than that damp oil soaked area I mentioned.
When I fist noticed it running rough I figured I was just low in the back tank so I switched to the front and it persisted which leads me to believe that if I had a problem it would be from the selector valve forward.
When I disconnected the pump feed to the to switch it to the jug I noticed the line had a steady stream of fuel coming out of it but plugging it back into the pump and trying to bleed it proved unsuccessful.
Incidentally, I noticed my electric pump no longer triggers with the key on. Still runs when jumped to the battery but nothing when plugged into the relay. Checked and re-checked all splices, connections, fuses, and terminals. All seems good, maybe I fried the relay??? I'm really trying to stay patient but this might just be the one that does me in...[emoji34]

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[Thewespaul]

What level is your fuel tank? Have you tried to see if it does it with both tanks?

 

[Mammoth73]

The rear tank was low but the front tank was full and it ran on the front tank a good 20 minutes before it finally sputtered out. it ran rough that whole 20 minutes tho except when it was idling.
I think tomorrow I'm gonna run a clear line from the pump to the selector valve to see if that's my issue. I figure this way if it is the hard line that's the issue it should run fine with the clear line and if not I should hopefully be able to see the air coming from my tanks.

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[Mammoth73]

Update: After talking with 283dfc and getting very helpful advice, I ran a clear line from the pump to the line coming from the tanks/ selector valve and I primed it with the mechanical pump. I then noticed an air bubble sitting at the high point in the line with a small bubble coming from the tanks and feeding the bigger bubble.
I'm talking a SMALL bubble. Like just barely noticeable, roughly every 5-10 seconds conning from the tank tube. It took me 5 minutes of watching the line with it idling just to confirm my eyes weren't playing tricks on me. I then ran a new temporary rubber line in place of the hard line to the rubber lines just before the selector to see if this was the issue... it wasn't.
My suspicion is that the bubble was there before but only until it got big enough did it choke out the fuel... but it seems to just stay constant. I can purge it out but almost immediately more bubbles come to occupy the space of the old one. Then it'll sit and run perfect but still feeding the air into the system. Once the bubble reaches a certain size it seems to stay that way with any additional air going up to the engine and not causing any noticeable issues.
I switched to the back tank and noticed substantial air coming thru which makes sense considering its almost empty. I'm about to go fill the rear tank and see if the bubbles persist. If they do then ill probably drop the front tank to gain access to the selector valve and replace all fittings to and from it. If they go away then I'll drop the front tank and replace the front tank lines.
Realistically I'll most likely replace every line can once I've got the front tank now but for the moment I just need a working truck until I can plan a time to do a full bulletproofing of the fuel system or at least a complete oem quality replacement of all fuel lines....
There are definitely times I wonder if I'm wasting my time on here but years of reading forums from others and the hundreds of solutions I've found from other users gives me hope that one day someone else will read this and be as thankful as I was for posts like this when I first started on cars. Even tho some of the posts I learned on were 10-14 years old when I read them, I still can think of a few threads in particular that I only wish I could let the OP know how much they've unknowingly helped me and how much undelivered credit they deserve.
That being said I'll update y'all when I find out what my next step is.

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