2000 Chevy Express 3500 6.5l td problems!
 

Hey guys. first time poster in here. i would like to thank everyone in advance for taking the time to help even just to read. my fiance just totaled her car and i need to get this running asap. hope i came to the right place!
ok so i bought this van with 200k miles . clean title and for 1300. many things have been replaced. my buddy is a good mechanic and knows his stuff but this van is being a turd.

It starts up a little slow. but does start up every time.
it is loud. not tooo loud when u get it going.
it accelerates nice and smooth. has boost, can hear the turbo.

BUT here is the issue. and sorry if i am hard to follow. i am more a motorcycle guy and terms confuse me haha.

Like i said acceleration is great, but say i want to go to 45. ill accelerate to 45 and then when i get there and am holding the pedal down to the "cruise" speed of 45, the van will just start to lose speed. my foot is still on the pedal though. it seems to only not do this at 90mph haha.
i feel like fuel is being consumed quickly and also another issue is that at idle it shakes. kinda like a beefed up muscle car when u rev it up.

i have heard that there is a screw in the injection pump that gets a little lose and that will cause it to do something like this.
Also it has the electronic gas pedal setup so i dont now if that may be the isue.

please any advice or things to check or anything like that would be awesome.

First go to the parts store and have it checked for trouble codes,write them down and post any that it has here-we will help decode them.

Second-there is no screw coming loose in the IP ,that applies to 93 and older trucks and then I haven't heard much of it unless tampered with.

Has it had the fuel filter changed lately?

You also need to verify that the lift pump that supplies the injection pump with fuel is working-try bleeding the fuel filter with the engine running.
If fuel comes out the bleeder and it keeps running-thats a good sign.
If you open the bleeder and it stalls and won't restart easily-theres a problem with the LP.

Vans are apparently different than the trucks so you might have to figure out a way to bleed the filter that I currently forget without a van in front of me.

That is the first things I can think of with the info given.