Van wont start

2001 GMCSavana 1500.  Before it stopped
working, at times while driving acted like it didn't
want to go. I would tap the gas a cpl times, would
stop doing that for a bit. I started having trouble
starting my van. For awhile would only start with a
jump, then nothing. Got a new battery. It did the
same thing for like a week, only starting with a
jump. It was fine almost a month. This time when it
wouldn't start, was no noise. Someone started it
from under my van and tried to install a new
ignition. That didn't work. He put in a new cranking
fuse, started fine for 3 days. Took it to another guy
who said it was the celanoid/starter. Worked great
for 3 days. It makes noise, sounds like it wants to
start, but doesn't. Took it to another guy and when
he tried starting it, something is smoking and
making a clunking noise. He thought maybe a
timing issue. He left and never came back. I had a
4th guy look at it, he said a tune up. My question is
what could it be. I can't afford to keep putting
money into the wrong thing. I can't afford another
vehicle either.