This is one I've personally never heard of before, and can't seem to find any instances of it anywhere online.

This 89 E150 with a 5.8L sat for at least a couple years before it came to be my problem, and I wasn't there when it was started for the first time so I have no history there, but the van drove for a few days, had it's oil changed, passed safety and emissions tests, and died on the side of the freeway with a crank/no start condition. It was towed into my driveway and my adventure starts from there.

The van has dual tanks, and after sitting for so long with horrible, horrible gas still in the tanks, both lift pumps and one of the sending units had completely rotted out and seized, so both tanks were dropped, both lift pumps replaced, a new fuel filter, and a new high pressure front pump installed. During the process of troubleshooting and replacing these parts, the engine cranked just fine, no noise, no issues whatsoever except for the no start. After getting the fuel system up to snuff and some new gas, the engine fired right up and idled just fine again. Drove it around, full power, nothing of concern at all. Until I shut it down for a few hours.

Now every time you attempt to start the van, there's a nasty nasty internal clank that sounds to me like top end valvetrain noise, and the engine spins over with what seems like zero (no joke) compression at all, just like you spun the engine over with no spark plugs installed. If you keep cranking for about 15-20 seconds, the clank starts to go away, and compression starts to build, until the engine studders and finally starts, flooded as hell at first, and then smoothes out to a perfect idle again. No noise, full power, no issues. Until you shut it off again and let it sit for an hour or two, sometimes it will start to exhibit similar but less severe symptoms only after a few minutes of downtime.

I can only assume that the lifters have bled down enough to collapse and cause hellacious noise, until the oil pump builds pressure back up and takes up the valve lash. What confuses the hell out of me though, is how this damn thing drove for days, killed the fuel pumps, and then cranked and cranked and cranked like crazy through all the fuel system tests, started back up, drove, and THEN developed this problem. Especially on enough cylinders to drop overall compression THAT bad, to where it litterally sounds like there's no spark plugs in it.

Basically, I guess I'm wanting to know if it's worthwhile to pull the intake and chase after the lifters and pushrods, or if anybody knows of another issue that could be causing this?

Thanks!!