Starting problems

[CarMAn2]

Hello,
My 98 firebird has 100,000 miles on it. Whenever I try to start it, it just rolls over for long periods of time before finally starting, and backfires occasionally while cranking. I have replaced the crank and cam sensor, and checked for fuel pressure. My fuel pressure is about 50psi, which sounds about right to me. The fuel pressure quickly drops to 15-20psi within and hour after the car is shut off, but as soon as I turn the key I immediately get the 50 psi in the line. Could this be related to my ignition switch? Any other ideas?
Thanks!
~Will

[86TATpi]

Could be a number of problems. Injectors, fuel pressure regulator. After the fuel pump primes and the pressure is around 50, within 10 minutes the pressure shouldn't drop more than 5 psi. This is from memory I can get the actual flow chart for testing fuel pressure later. Hook a spark tester to make sure it's not in the ignition. Could also be in the air metering. If, for example, the MAF sensor is failing you can have a starting problem. The car may not stay running, but you may not get a SES lamp.

[CarMAn2]

Thank you fo rthe advise. Is there an easy way to test the pressure regulator. It is extremely hard to get to because it is way in the back under the cowl. I have tapped on it with a screwdriver and the engine RPMs change sometimes when I do that. Thanks again
~Will