Check the Compression and see what kind of readings you're getting. If you don't have a
compression gage, take a Sparkplug out and put something over the hole, like a ratchet handle
or such thats so large that it can't be sucked into the eng and turn the motor over and see if
you get a healthy puff of air coming out on the compression stroke. The compression stroke will
be when NO valves are open thus the only place for compressed air to go is thru the sparkplug
hole. It should be near like 100 LBS psi blast of air. If it's weak, I would suspect Cylinder Washout or some call it washdown.
Before cranking the eng over, disconnect the wire from the Ballast or resistor OR pull a fuse
for the fuel pump. IE; dis-able injectors.
There's a few threads here about cyl washout and the cure.
If it is a case of cyl washout post back if you don't know how to cure it. Hope this helps.