It's like picking up water with your finger on the end of a straw.
A leak anywhere in the fuel supply/return system breaks the vacuum and lets air in.

 

Update:
Got the OFV in the mail, thank you LarryB, pretty nice little sealed baggy, instructions and rubber gloves, came fast too considering I am in AK.

I put the new OFV on and no dice. Still tough to start, will run for a few seconds as long as I give it some pedal, let off and it dies. Does that for about 20 seconds, then it will idle fine on its own, but misses and sputters at 1500, almost can't even go to 2000.

I know return line is on the list for the hard start, which it did again by the way, in only as long as it took me to pour 5gal into the tank. I am at 7/8 tank too. But the return shouldn't relate to the sputtering right? I mean if the OFV is working, the supply could be dumping on the ground and it should run as long as the supply line is good.

This just leaves the LP being shot or the timing did somehow slip between me parking it when it ran fine, sitting for 4 months, and now. No driving, nothing, can it slip like that?

I guess next is check FP. I have a little 20$ oil pressure gauge, just need to buy a tap and get it connected.

Am I on the right path still? This seems like a better next step than setting timing, would need several new tools for that.

 

Right path in my book.

 

Update:
Tapping that bolt was a PITA. Maybe I just had a crappy bit, or doing it without a big vice was why. But got the fuel gauge in. I adjusted the needle valve and bled until I got fuel at the back of the gauge, no air. Turned the needle valve down just until the needle stopped bouncing around and it settled at about 18psi. That was idle, maybe just getting a really good long idle made it run better, it would rev to 2000 rpm now before sputtering. I was able to take it for a drive to get some real FP readings, that gauge seems pretty slow to respond, but any looser on the needle valve and its bouncing like crazy.

While crusing at 45mph, something like 1500rpm it was about 10psi. And under moderate accel it dropped to probably like 5-8 range, gauge isn't hash marked from 0-10psi. This points to the LP now right? No fuel leaks and those are the pressures I am getting. I was surprised though at the idle psi at first, seemed good, but guess it just can flow any kind of volume and maintain that pressure.

I bought the LP and the studs to replace the stock bolts, I will tackle that next, really hope it works!

By the way, I think this sad old 47RH needs an adjustment, I think I have two gears: one big mixed gear that gets me up to about 45, then a very obvious overdrive.

Thanks for the help so far, getting the truck better!

 

Since you have the gauge now, pinch off the return line, if it doesn't fly up to 60 PSI or so, then yea, Lift Pump.

 

OK, truck was idling at about 18psi, got under and pinched the hose, wife said it slowly climbed to about 35psi at most.

Tomorrow I will be doing that lift pump then! Nice having that gauge.

 

Buy some studs too, it will make the job 100 times easier.
Toss the stock pump bolts and replace with a pair of 8mm x 30mm x 1.25 pitch studs with nuts

 

Well, it took 5 hours but got the new pump on. That elbow needed a torch to get it off the old pump. Went the stud method, can't imagine not doing that.

Truck now idles at 30psi and at 2000rpm ,no load, it's about 45-50psi!!!! Man it feels better.

Though I have two things that were temporary fixes:

1) the short hose between the pump and filter was silicon heater hose I found out once I pulled it off. No dice on the real part, will get that from dodge, put the silicone back on though for now.

2) Intake horn gasket came off in pieces, was nasty. No dice either at napa so I used high temp RTV! I hope that holds up alright for a day or two.

So truck runs much, much better. Though still at about 2500-2800 rpm (I don't really go that high anyway) but it has a tiny miss or stumble. Could that be a little timing slip, or valve clearances? I think that's next just for good measure (valves)

Thanks for all the help!

 

Beware, fuel pressure in excess of 45 psi can blow out expensive to replace internal injection pump seals. Your oil level will increase and dipstick will smell like diesel.
Sounds like someone has tampered with the overflow valve or your gauge isn't reading right.

 

I will look at that again, the OFV is brand new from LarryB, installed that a week ago. Gauge was a 20$ cheapie from O'Reillys. I could have been reading the numbers incorrectly too.