96 Silverado Hard Starting

1996
350,5.7

After putting everything back together after replacing the intake manifold gasket the engine is very hard to crank but every once in a while (4 or 5 start attempts)
it starts perfectly and runs great, but if I turn it off it goes through the same thing again hard cranking.

Is it possible the rotor or distributor is on backwards? (I changed the rotor and am pretty sure I put distrubutor back in same spot but just trying to think of what it might be or would it not start at all if this was the problem.
Would a crankshaft position sensor cause this behavior? I don't have andy code testers but would go get one if this would help diagnose.
I am trying to narrow down the possiblilities before taking it in for a diagnosis.

Any suggestions would be great

Gary

BUY A NEW TRUCK, ITS THAT SIMPLE

If the engine is out of timing this will happen. Most of the time when you take out the distributor, even if you mark it, you have to have a scan tool than will display the cam position offset to set the cam position sensor to 0* +/- 2*.

If the engine is out of timing this will happen. Most of the time when you take out the distributor, even if you mark it, you have to have a scan tool that will display the cam position offset to set the cam position sensor to 0* +/- 2*.

hi, main is 2001 was too hard to start, I dicovered that fuel pump was not holding presure; just change hose betwin pump and module and is working fine. good luck