Hard start/long cranking time

[Calvin & Diana Craig]

Sometimes this is indicative of the fuel pump going bad.  Sometimes, as was
the case on a '91 SHO I had, it is the cam or crank position sensor....more
likely cam.  My S4 also had a similar problem and it turned out to be the
fuel pressure regulator.  The pressure regulator is cheap, about $35, and
literally takes about 15 minutes to change.  I would try this before any
other fix, unless you are 100% sure it is not it.  It does take quite awhile
when the fuel pressure drops to 0 to re-pressurize.  I would crank for a
good 6-10 seconds on the S4 before getting it to start.  The regulator was
also elusive because it didn't ALWAYS lose pressure (i.e. when I was
measuring it).  I replaced the fuel pump first, $200 including labor, then
the problem was still there, so that's when I replaced the
regulator...problem gone.
--Calvin